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Accepted papers to appear in an upcoming issue

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Nodal-line dynamics via exact polynomial solutions for coherent waves traversing aberrated imaging systems

David Paganin, Timothy Petersen, and Mario Beltran

Doc ID: 313314 Received 13 Nov 2017; Accepted 19 Jan 2018; Posted 19 Jan 2018  View: PDF

Abstract: We obtain exact polynomial solutions for two-dimensional coherent complex scalar fields propagating through arbitrary aberrated shift-invariant linear imaging systems. These are used to model nodal-line dynamics of coherent fields output by such systems.

Real-time spectral characterization of a photon pair source using a chirped supercontinuum seed

Jennifer Erskine, Duncan England, Connor Kupchak, and Benjamin Sussman

Doc ID: 313562 Received 17 Nov 2017; Accepted 19 Jan 2018; Posted 19 Jan 2018  View: PDF

Abstract: Photon pair sources have wide ranging applications in a variety of quantum photonic experiments and protocols. Many of these protocols require well controlled spectral correlations between the two output photons. However due to low cross-sections, measuring the joint spectral properties of photon pair sources has historically been a challenging and time-consuming task. Here, we present an approach for the real-time measurement of the joint spectral properties of a fiber-based four wave mixing source. We seed the four wave mixing process using a broadband chirped pulse, studying the stimulated process to extract information regarding the spontaneous process. In addition, we compare stimulated emission measurements with the spontaneous process to confirm the technique's validity. Joint spectral measurements have taken many hours historically and several minutes with recent techniques. Here, measurements have been demonstrated in 5-30 seconds depending on resolution, offering substantial improvement. Additional benefits of this approach include flexible resolution, large measurement bandwidth, and reduced experimental overhead.

Tomography of asymmetric molecular orbitals with one-color inhomogeneous field

Hua Yuan, Lixin He, Feng Wang, Baoning Wang, Xiaosong Zhu, Pengfei Lan, and Peixiang Lu

Doc ID: 318111 Received 20 Dec 2017; Accepted 19 Jan 2018; Posted 19 Jan 2018  View: PDF

Abstract: We demonstrate to image asymmetric molecular orbitalsvia high-order harmonic generation in a one-colorinhomogeneous field. Due to the broken inversionsymmetry of the inhomogeneous field in space, thereturning electrons with energy in a broad range can beforced to recollide from only one direction for all theorientation angles of molecules, which therefore can beused to reconstruct asymmetric molecular orbitals. Followingthe procedure of molecular orbital tomography,the highest occupied molecular orbital of CO is satisfactorilyreconstructed with high-order harmonic spectradriven by the inhomogeneous field. This scheme ishelpful to relax the requirement of laser conditions andalso applicable to other asymmetric molecules.

Controllable photonic crystal with Raman gain in a coherent atomic medium

Yanpeng Zhang, Jingliang Feng, xing liu, Jiteng Sheng, Yiqi Zhang, Zhaoyang Zhang, and Min Xiao

Doc ID: 318502 Received 27 Dec 2017; Accepted 18 Jan 2018; Posted 19 Jan 2018  View: PDF

Abstract: With two sets of standing-wave fields built in a thermal rubidium vapor, we have established a controllable photonic crystal with gain in a coherently-prepared N-type four-level atomic configuration. First, the photonic lattice constructed by a resonant standing-wave coupling field results in a spatially modulated susceptibility and makes the signal field diffract in a discrete manner under the condition of electromagnetically induced transparency. Then, with the addition of the standing-wave pump field, the N-type atomic medium can induce a periodic Raman gain on the signal field, which can be effectively controlled by tuning the pertinent atomic parameters. The experimental demonstration of such a real-time reconfigurable gain/absorption photonic crystal structure can pave the way for realizing desired applications predicted in the gain-modulated periodic optical systems.

Silicon Microdisk-Based Full Adders for Optical Computing

Zhoufeng Ying, Zheng Wang, Zheng Zhao, Shounak Dhar, David Pan, Richard Soref, and Ray Chen

Doc ID: 314674 Received 30 Nov 2017; Accepted 18 Jan 2018; Posted 19 Jan 2018  View: PDF

Abstract: Due to the projected saturation of Moore’s law as well as the drastically increasing trend of bandwidth with lower power consumption, silicon photonics has emerged as one of the most promising alternatives that has attracted a lasting interest due to the accessibility and maturity of ultra-compact passive and active integrated photonic components. However, up to now, most of the relevant research about optical computing still focuses upon the realization of fundamental logic gates. In this paper, we demonstrate a ripple-carry electro-optic two-bit full adder using microdisks, which replaces the core part of an electrical full adder by optical counterparts and uses light to carry signals from one bit to the next with high bandwidth and low power consumption per bit. All of the control signals of the operands are applied simultaneously within each clock cycle. Thus, the severe latency issue that accumulates as the size of the full adder increases can be circumvented, allowing for an improvement in computing speed and a reduction in power consumption. This approach paves the way for the future high-speed optical computing systems in the post-Moore’s-law era.

Performance Comparisons between Semiconductor and Fiber Amplifier Gain Assistance in Recirculating-Frequency-Shifter

Xiaoxi Wang and Shayan Mookherjea

Doc ID: 314960 Received 04 Dec 2017; Accepted 18 Jan 2018; Posted 19 Jan 2018  View: PDF

Abstract: Recirculating frequency shifter (RFS) loops can be used for electronically-programmable, variable-spacing multi-line spectrum generation, which can benefit the development of fully-flexible optical communications and other frequency comb applications. Here, we report on and explain the observation of significant performance variations between chip-based gain in semiconductor optical amplifiers (SOA) and fiber-based gain in erbium doped fiber amplifiers (EDFA) when used as the gain element in the RFS. Previously, SOAs and EDFAs have been demonstrated in different RFS experiments and studied separately from each other, and discussion mainly focused on the noise from amplified spontaneous emission (ASE). We show that SOA effects including four wave mixing (FWM) can be measured which impose limits to the wavelength spacing of the combs, and that this effect is mitigated by increasing the RF drive frequency of the RFS and operating SOA in deeper saturation.

Pulse carving using nanocavity-enhanced nonlinear effects in photonic crystal Fano structures

Dagmawi Bekele, Yi Yu, Hao Hu, Pengyu Guan, Luisa Ottaviano, Michael Galili, Leif Oxenlowe, Kresten Yvind, and Jesper Mork

Doc ID: 315325 Received 12 Dec 2017; Accepted 18 Jan 2018; Posted 19 Jan 2018  View: PDF

Abstract: We experimentally demonstrate the use of a photonic crystal Fano resonance for carving-out short pulses from long-duration input pulses. This is achieved by exploiting an asymmetric Fano resonance combined with carrier induced nonlinear effects in a photonic crystal membrane structure. The use of a nanocavity concentrates the input field to a very small volume leading to an efficient nonlinear resonance shift that carves a short pulse out of the input pulse. Here, we demonstrate shortening of ~ 500 ps and ~ 100 ps long pulses to ~ 30 ps and ~ 20 ps pulses respectively. Furthermore, we demonstrate error-free low duty cycle return-to-zero (RZ) signal generation at 2 Gbit/s with energy consumption down to ~ 1 pJ/bit and a power penalty of ~ 2 dB. The device physics and limitations are analyzed using nonlinear coupled-mode theory.

Hilbert-Huang single-shot spatially multiplexed interferometric microscopy

José Ángel Picazo-Bueno, Maciej Trusiak, Javier Garcia-Monreal, Krzysztof Patorski, and Vicente Mico

Doc ID: 315559 Received 12 Dec 2017; Accepted 18 Jan 2018; Posted 19 Jan 2018  View: PDF

Abstract: H2S2MIM (initials incoming from Hilbert-Huang Single-shot Spatially Multiplexed Interferometric Microscopy) is presented as the implementation of a robust, fast and accurate single-shot phase estimation algorithm with an extremely simple, low cost and highly stable way to convert a bright field microscope into a holographic one using partially coherent illumination. All together, H2S2MIM adds high-speed (video frame rate) quantitative phase imaging capability to a commercially available non-holographic microscope with improved phase reconstruction (coherence noise reduction). The technique has been validated using a 20X/0.46NA objective in a regular Olympus BX-60 upright microscope for static as well as dynamic samples showing perfect agreement with the results retrieved from temporal phase shifting algorithm.

Optical Rewritable Liquid Crystal Displays without Front Polarizer

Cuiling Meng, Man chun Tseng, Shutuen Tang, and Hoi-Sing Kwok

Doc ID: 313611 Received 27 Nov 2017; Accepted 18 Jan 2018; Posted 18 Jan 2018  View: PDF

Abstract: A front polarizer-free optically rewritable (ORW) liquid crystal displays (LCDs) has been made via a hybrid alignment configuration with dye-doped LCs. The hybrid structure consists of one optically active planar and one optically passive homeotropic alignment layer. The rewritability of the device is achieved by photo- reorienting the azo dye molecules in the active planar alignment layer. The dye doped in LCs function as a polarizer by following the LCs alignment via a guest-host effect so that the front polarizer can be eliminated. This makes the device more compact and easier to operate for image erasing and rewriting. The image rewriting time only requires ~9.0s, which is determined by the exposure energy and LC parameters. The hybrid-mode dye-doped optically rewritable (DDORW) LCD devices could find applications in E-paper, transparent display and various photonics devices.

Two-dimensional electronic-Raman spectroscopy

Zhengyang Zhang, ADRIANA HUERTA-VIGA, and Howe-Siang Tan

Doc ID: 318185 Received 21 Dec 2017; Accepted 18 Jan 2018; Posted 18 Jan 2018  View: PDF

Abstract: We present a new technique, two-dimensional electronic-Raman spectroscopy (2DER), that combines femtosecond stimulated Raman spectroscopy (FSRS) and a pulse shaper assisted two-dimensional spectroscopic scheme for the actinic pump. The 2DER spectrum presents the initial actinic excitation wavelength with nanometer spectral resolution in the first axis, and the detected stimulated Raman spectra in the second axis. We use 2DER to measure the correlation of the electronic and vibrational states in the photosynthetic accessory pigment β-carotene and revealed its photoexcited state manifold.

Radiation hardness of Ce-doped sol-gel silica fibers forHigh Energy Physics applications

Francesca Cova, Federico Moretti, Mauro Fasoli, Norberto Chiodini, Kristof Pauwels, Etiennette Auffray, Marco Lucchini, stefania baccaro, ALESSIA CEMMI, Hana Bartova, and Anna Vedda

Doc ID: 313455 Received 15 Nov 2017; Accepted 17 Jan 2018; Posted 18 Jan 2018  View: PDF

Abstract: The results of irradiation tests on Ce-doped sol-gel silica using X- and g-rays up to 10 kGy are reported, in order to investigate the radiation hardness of this material for high energy physics applications. Sol-gel silica fibers with Ce concentrations of 0.0125 mol% and 0.05 mol% are characterized by means of optical absorption and attenuation length measurements beforeand after irradiation. The two different techniques give comparable results, evidencing the formation of a main broad radiation-induced absorption band, peaking at about 2.2 eV, related to radiation-induced color centers. The results are compared with those obtained on bulk silica. This study reveals that an improvement of the radiation hardness of Ce-doped silica fibers canbe achieved by reducing Ce content inside the fiber core, paving the way for further material development.

87-fs mode-locked Tm,Ho:CaYALO4 laser at ~2043 nm

Yongguang Zhao, Yicheng Wang, Xuzhao Zhang, Xavier Mateos, Zhongben Pan, Pavel Loiko, Wei Zhou, Xiaodong Xu, Jun Xu, Deyuan SHEN, Soile Suomalainen, Antti Harkonen, Mircea Guina, Uwe Griebner, and Valentin Petrov

Doc ID: 317999 Received 19 Dec 2017; Accepted 16 Jan 2018; Posted 19 Jan 2018  View: PDF

Abstract: We report on the first sub-100-fs mode-locked Ho3+-laser in the 2-µm spectral range employing a disordered co-doped Tm,Ho:CaYAlO4 (Tm,Ho:CALYO) crystal as a gain medium. Pulses as short as 87 fs are produced with an average output power of 27 mW at 80.45-MHz repetition rate. An output power of 96 mW is reached for a pulse duration of 98 fs.

Watt-level widely tunable femtosecond mid-infrared KTiOAsO4 optical parametric oscillator pumped by a 1.03 μm Yb:KGW laser

Hao Meng, Zhaohua Wang, wenlong tian, Huijun He, SHAOBO FANG, and Zhiyi Wei

Doc ID: 318524 Received 27 Dec 2017; Accepted 15 Jan 2018; Posted 19 Jan 2018  View: PDF

Abstract: A high power, high repetition rate, broadband tunable femtosecond optical parametric oscillator (OPO) is constructed based on KTiOAsO4 crystal, pumped by a 75.5 MHz mode-locked Yb:KGW laser. With 7 W pump power, the OPO generates as much as 2.32 W of signal power at 1.55 μm and 1.31 W of idler power at 3.05 μm, corresponding to a total conversion efficiency of 51.8%. Operating at 151 MHz repetition rate, the wavelength of the signal covers 1.41 to 1.71 μm with a tunable idler range of 2.61-3.84 μm. The idler bandwidth is more than 180 nm over the entire mid-infrared range. By compensating intra-cavity dispersion, the signal pulse has a nearly Fourier transform-limited duration of 129 fs at 1.52 μm.

Subwavelength-grating contra-directional couplers for large stopband filters

Dominique Charron, Jonathan St-Yves, Omid Jafari, Sophie LaRochelle, and Wei Shi

Doc ID: 315106 Received 08 Dec 2017; Accepted 15 Jan 2018; Posted 16 Jan 2018  View: PDF

Abstract: Manipulating the coupling coefficient at subwave- length scales provides an additional degree of freedom in designing integrated Bragg gratings. We demon- strate asymmetric contra-directional couplers (contra- DCs) using side-wall-corrugated subwavelength grat- ing (SWG) waveguides for broadband add-drop Bragg filters. We show that SWG can effectively increase the overlap of coupled modes and thus the photonic band gap. The measured spectra show good agreement with the prediction of photonic band structure simu- lations. A record bandwidth of 4.07 THz (33.4 nm) has been achieved experimentally. A four-port Bragg resonating filter made of a phase-shifted Bragg grat- ing SWG contra-DC is also demonstrated for narrow- band (near 100 GHz) filtering. All these devices are achieved on the 220-nm silicon-on-insulator platform with a compact footprint of less than 1000 μm2. These large-stopband filters may find important applications such as band splitting, reconfigurable channel band switching, bandwidth-tunable filtering and dispersion engineering.

Three-dimensional inverse synthetic aperture lidar imaging for long-range spinning targets

Di Mo, wang ran, NING WANG, Tian Lv, Ke-Shu Zhang, and Yi-Rong Wu

Doc ID: 317898 Received 18 Dec 2017; Accepted 15 Jan 2018; Posted 16 Jan 2018  View: PDF

Abstract: We present a three-dimensional (3D) imaging method for long-range spinning targets. This method acquires multi-angle two-dimensional (2D) images of spinning targets by inverse synthetic aperture lidar (ISAL) imaging technique. The 3D distribution of the scattering coefficients of a target has a mapping relationship with the series of 2D images. This mapping is analyzed and 3D Hough Transform is used to implement inverse mapping. The parameter space of the Hough transform is the estimation of the 3D distribution of the scattering coefficients. The 3D point spread function (PSF) obtained by the method has narrow main lobe widths and sufficiently low side lobes to achieve high image quality, which is verified by computer simulations. In the simulations, the main lobe widths in the three dimensions are 0.29 cm, 0.29 cm and 3.48 cm, respectively. In outdoor experiments, 3D images of targets at 1 km away from the lidar were obtained. The images clearly show the 3D shape of targets.

Engineering spectrally unentangled photon pairs from nonlinear microring resonators by pump manipulation

Jesper Christensen, Jacob Koefoed, Karsten Rottwitt, and Colin McKinstrie

Doc ID: 313444 Received 15 Nov 2017; Accepted 15 Jan 2018; Posted 16 Jan 2018  View: PDF

Abstract: The future of integrated quantum photonics relies heavily on the ability to engineer refined methods for preparing the quantum states needed to implement various quantum protocols. An important example of such states are quantum-correlated photon pairs, which can be efficiently generated using spontaneous nonlinear processes in integrated microring-resonator structures. In this work, we propose a method for generating spectrally unentangled photon pairs from a standard microring resonator. The method utilizes interference between a primary and a delayed secondary pump pulse to effectively increase the pump spectral width inside the cavity. This enables on-chip generation of heralded single photons with state purities in excess of 99 % without spectral filtering.

High efficiency all-fiber vectorial laser using a long-period fiber grating

Chen Ruishan, jinghao wang, z xq, Anting Wang, Hai Ming, Feng Li, Dick Chung, and Qiwen Zhan

Doc ID: 313950 Received 22 Nov 2017; Accepted 15 Jan 2018; Posted 16 Jan 2018  View: PDF

Abstract: We demonstrate a novel all-fiber laser generating cylindrical vector beams (CVBs) with high slope efficiency and low threshold by introducing a long-period fiber grating (LPFG) into the laser cavity. Highly efficient mode conversion is realized by an LPFG at ~1548 nm. Mode selection and spectrum filtering are achieved in combination with a two-mode fiber Bragg grating (TM-FBG). The fiber laser operates at a single wavelength of 1547.95 nm with a 30 dB linewidth of less than 0.18 nm and a side-mode suppression ratio (SMSR) of more than 56 dB. The lasing threshold and slope efficiency of the laser are 24.5 mW and 35.41%, respectively. The output power is 72 mW with an absorbed pump power of 225 mW. The variation of slope efficiency with respect to the reflectivity of the TM-FBG is investigated. Through adjusting the intra-cavity polarization controller (PC), high purity radially and azimuthally polarized beams are both obtained.

3-bit writing of information in nanoporous glass by single sub-microsecond burst of femtosecond pulses

Sergey Fedotov, Andrey Okhrimchuk, Alexey Lipatiev, Alexander Stepko, Kseniya Piyanzina, Georgiy Shakhgildyan, Mikhail Presniakov, Ivan Glebov, Sergey Lotarev, and Vladimir N Sigaev

Doc ID: 314226 Received 28 Nov 2017; Accepted 15 Jan 2018; Posted 16 Jan 2018  View: PDF

Abstract: We have found that a single sub-microsecond burst of femtosecond laser pulses produces a sub-micron cavity possessing the homogeneous birefringence with slow axis orientation perpendicular to polarisation of the laser beam in high-silicate nanoporous glass. Retardance and the root mean square of slow axis orientation are investigated in dependence on the energy and the number of pulses in the burst. A burst of just three pulses with 98 ns inter-pulse intervals has been shown to induce homogeneous birefringence and a burst of four pulses has provided birefringence with retardance of 35 nm which is sufficient for reliable read out of the information recorded with multilevel encoding in slow axis orientation. A text file has been recorded and read out in an array of birefringent cavities, each carrying 3 bits of information. The sub-microsecond burst of femtosecond pulses paves the way for a multiple increase of the rate of digital information recording with multilevel encoding in glass.

Ultra-Low-Threshold InGaN/GaN Quantum Dot Micro-ring Lasers

Danqing Wang, Tongtong Zhu, Rachel Oliver, and Evelyn Hu

Doc ID: 315014 Received 11 Dec 2017; Accepted 15 Jan 2018; Posted 16 Jan 2018  View: PDF

Abstract: In this work, we demonstrate ultra-low threshold, optically pumped, room temperature lasing in GaN microdisk and micro-ring cavities containing InGaN quantum dots (QDs) and fragmented quantum wells (fQWs), with the lowest measured threshold at a record low of 6.2 μJ/cm^2. We observe a systematic decrease in lasing threshold of micro-rings with decreasing pump volume. The photon loss rate, γ, increases with increasing inner ring diameter, and leads to a systematic decrease in the post-threshold slope efficiency, while the quality factor (Q) of the lasing mode remains largely unchanged. A careful analysis using finite-difference time-domain (FDTD) simulations attributes the increased γ to the loss of photons from lower quality higher order modes during amplified spontaneous emission (ASE).

CMOS compatible source of single photons at near-visible wavelengths

Robert Cernansky, Francesco Martini, and Alberto Politi

Doc ID: 308961 Received 21 Nov 2017; Accepted 15 Jan 2018; Posted 16 Jan 2018  View: PDF

Abstract: We demonstrate on chip generation of correlated pairs of photons in the near-visible spectrum using a CMOS compatible PECVD Silicon Nitride photonic device. Photons are generated via spontaneous four wave mixing enhanced by a ring resonator with high quality Q-factor of 320,000 resulting in a generation rate of 950,000 pairs/mW. The high brightness of this source offers the opportunity to expand photonic quantum technologies over a broad wavelength range and provides a path to develop fully integrated quantum chips working at room temperature.

Phase-synchronous undersampling in nonlinear spectroscopy

Lukas Bruder, Marcel Binz, and Frank Stienkemeier

Doc ID: 318519 Received 27 Dec 2017; Accepted 14 Jan 2018; Posted 16 Jan 2018  View: PDF

Abstract: We introduce the concept of phase-synchronous undersampling in nonlinear spectroscopy. The respective theory is presented and validated experimentally in a phase-modulated quantum beat experiment by sampling high phase modulation frequencies with low laser repetition rates. The advantage of undersampling in terms of signal quality and reduced acquisition time is demonstrated and breakdown conditions are identified. The presented method is particularly beneficial for experimental setups with limited signal/detectionrates.

Cavity solitons in a microring dimer with gain and loss

Carles Milian Enrique, Yaroslav Kartashov, Dmitry Skryabin, and Lluis Torner

Doc ID: 315477 Received 11 Dec 2017; Accepted 14 Jan 2018; Posted 18 Jan 2018  View: PDF

Abstract: We address a pair of vertically coupled microring resonators with gain and loss pumped by a single-frequency field. Coupling between microrings results in a twofold splitting of the single microring resonance that increases when gain and losses decrease and that gives rise to two different cavity soliton (CS) families. We show that the existence regions of CSs are tunable and that both CS families can be stable in the presence of an imbalance between gain and losses in the two microrings. These findings enable experimental realization of frequency combs in configurations with active microrings and contribute towards the realization of compact multisoliton comb sources.

Polarization- and wavelength-resolved near-field imaging of complex plasmonic modes in Archimedean nanospirals

Jordan Hachtel, Roderick Davidson, Elena Kovalik, Scott Retterer, Andrew Lupini, Richard Haglund, Benjamin Lawrie, and Sokrates Pantelides

Doc ID: 318651 Received 02 Jan 2018; Accepted 13 Jan 2018; Posted 18 Jan 2018  View: PDF

Abstract: Asymmetric nanophotonic structures enable a wide range of opportunities in optical nanotechnology because they support efficient optical nonlinearities mediated by multiple plasmon resonances over a broad spectral range. The Archimedean nanospiral is a canonical example of a chiral plasmonic structure because it supports even-order nonlinearities that are not generally accessible in other locally symmetric geometries. However, the complex spiral response makes nanoscale experimental characterization of the plasmonic near-field structure highly desirable. Here we employ high-efficiency, high-spatial-resolution cathodoluminescence imaging in a scanning transmission electron microscope to describe the spatial, spectral, and polarization response of plasmon modes in the nanospiral geometry.

Mid-infrared multispectral tissue imaging using a chalcogenide fiber supercontinuum source

Christian Petersen, Nikola Prtljaga, Mark Cunningham Farries, Jon Ward, Bruce Napier, Gavin Lloyd, Jayakrupakar Nallala, Nicholas Stone, and Ole Bang

Doc ID: 314140 Received 22 Nov 2017; Accepted 13 Jan 2018; Posted 19 Jan 2018  View: PDF

Abstract: We present the first demonstration of mid-infrared supercontinuum tissue imaging at wavelengths beyond 5 μm using a fiber-coupled supercontinuum source spanning 2-7.5 μm. The supercontinuum was generated in a tapered large mode area chalcogenide photonic crystal fiber in order to obtain broad bandwidth, high average power, and single-mode output for diffraction-limited imaging performance. Tissue imaging was demonstrated in transmission at selected wavelengths between 5.7 μm (1754 cm-1) and 7.3 μm (1370 cm-1) by point scanning over a sub-mm region of colon tissue, and the results were compared to images obtained from a commercial instrument.

Group refractive index quantification using Fourier domain short coherence Sagnac interferometer

Risto Montonen, Ivan Kassamakov, Peter Lehmann, Kenneth Osterberg, and Edward Hæggström

Doc ID: 315401 Received 11 Dec 2017; Accepted 12 Jan 2018; Posted 17 Jan 2018  View: PDF

Abstract: The group refractive index is important in length calibration of Fourier domain interferometers by transparent transfer standards. We demonstrate accurate group refractive index quantification using a Fourier domain short coherence Sagnac interferometer. Because of a justified linear length calibration function, the calibration constants cancel out in the evaluation of the group refractive index which is then obtained accurately from two uncalibrated length measures. Measurements of two standard thickness coverslips revealed group indices of 1.5426 ± 0.0042 and 1.5434 ± 0.0046, with accuracies quoted at 95% confidence level. This agreed with the dispersion data of coverslip manufacturer and therefore validates our method. Our method provides a sample specific and accurate group refractive index quantification using the same Fourier domain interferometer that is to be calibrated for the length. This reduces significantly the requirements of the calibration transfer standard.

Intensity noise behaviour of an InAs/InGaAs quantum dot laser emitting on ground-state and excited-state

Robert Pawlus, Lorenzo Columbo, Paolo Bardella, Stefan Breuer, and Mariangela Gioannini

Doc ID: 314564 Received 29 Nov 2017; Accepted 12 Jan 2018; Posted 16 Jan 2018  View: PDF

Abstract: We experimentally and numerically study the amplitude stability of an InAs/InGaAs quantum dot laser emitting simultaneously on ground-state (GS) and excited-state (ES) at center wavelengths 1245nm and 1168nm respectively. The stability is quantified by spectrally-resolved noise current analysis in dependence on the laser injection current. We find a reduction of the amplitude noise of up to 4 dB when GS and ES emit simultaneously. Simulations based on a rate equation model confirm the reduction in noise and suggest the cascaded GS and ES carrier paths as the relevant underlying mechanism.

Absolute distance measurement by multi-heterodyne interferometry using electro-optic triple-comb

Xianyu Zhao, XingHua Qu, FuMin Zhang, Yuhang Zhao, and Guoqing Tang

Doc ID: 315067 Received 06 Dec 2017; Accepted 12 Jan 2018; Posted 16 Jan 2018  View: PDF

Abstract: We experimentally demonstrated a method for absolute distance measurement using a triple-comb-based multi-heterodyne interferometer, which has the capacity to balance the non-ambiguous range, resolution, update rate and cost simultaneously. Three flattop electro-optic combs generated by cascaded intensity and phase modulators were adopted to form a measurement scheme including rough and fine measurements, and the unknown distance was determined by detecting the phase changes of the consecutive synthetic wavelengths. Actual tests proved an agreement within 750 nm over 80 m distance at the 167 μs update rate, corresponding to 10¬⁸ level in relative.

Measurement of the topological charges of vortex vector optical fields with a space-variant half-wave plate

Gui-Geng Liu, Ke Wang, Yun-Han Lee, Dan Wang, Ping-Ping Li, Fangwang Gou, Yongnan Li, Chenghou Tu, Shin-Tson Wu, and Hui-Tian Wang

Doc ID: 315076 Received 06 Dec 2017; Accepted 12 Jan 2018; Posted 12 Jan 2018  View: PDF

Abstract: Vortex vector optical fields (VVOFs) refer to a kind of vector optical fields with an azimuth-variant polarization and a helical phase, simultaneously. Such a VVOF is defined by the topological charges of both the polarization vortex and the phase vortex, which are related to the orbital angular momentum (OAM). We present a simple method to measure the topological charges of VVOFs by using a space-variant half-wave plate (SV-HWP). The geometric phase grating of the SV-HWP diffracts a VVOF into ±1 orders with orthogonally left- and right-handed circular polarizations. By inserting a polarizer behind the SV-HWP, the two circular polarization states project into the linear polarization and then interfere with each other to form the interference pattern, which enables the direct measurement of the topological charges of both the polarization vortex and the phase vortex.

Single-pulse writing of a concave microlens array

Xiao-Wen Cao, Qi-Dai Chen, Lei Zhang, Zhen-Nan Tian, Qian-Kun Li, Lei Wang, Saulius Juodkazis, and Hong-Bo Sun

Doc ID: 315529 Received 12 Dec 2017; Accepted 12 Jan 2018; Posted 12 Jan 2018  View: PDF

Abstract: This work developed a method of femtosecond laser (fs-laser) parallel processing assisted with wet etching to fabricate 3D micro optical components. A 2D fs-laser spot array with designed spatial distribution was generated by a Spatial Light Modulator (SLM). A single pulse exposure of entire array was used for parallel processing. By subsequent wet etching, a close-packed hexagonal arrangement 3D concave microlens array (CMLA) on curved surface with radius of approximately 120 μm was fabricated, each unit lens of which has designable spatial distribution. Characterisation of imaging was carried out by microscope and showed a unique imaging property in multi-planes. This method provides a parallel and efficient technique to fabricate 3D micro-optical devices for applications in optofluidics, optical communication and integrated optics.

Phase conjugate digital inline holography (PCDIH)

Daniel Guildenbecher, Kathryn Hoffmeister, Marley Kunzler, Daniel Richardson, and Sean Kearney

Doc ID: 313111 Received 09 Nov 2017; Accepted 12 Jan 2018; Posted 12 Jan 2018  View: PDF

Abstract: Digital inline holography (DIH) provides instantaneous three-dimensional (3D) measurements of diffracting objects; however, phase disturbances in the beam path can distort the imaging. In this letter, a phase conjugate digital inline holography (PCDIH) configuration is proposed for removal of phase disturbances. Brillouion-enhanced four-wave mixing produces a phase conjugate signal which back propagates along the DIH beam path. Results demonstrate removal of distortions caused by gas-phase shocks to recover 3D images of diffracting objects.

Ultrasound detection at fiber end-facets with surface plasmon resonance cavities

xin zhou, De Cai, Xiaolong He, Sung-Liang Chen, Xueding Wang, and Tian Yang

Doc ID: 308449 Received 05 Oct 2017; Accepted 12 Jan 2018; Posted 12 Jan 2018  View: PDF

Abstract: Ultrasound detection is performed by measuring laser reflection off a surface plasmon resonance cavity which is integrated at a single-mode fiber’s end facet. It shows a noise equivalent pressure of 5.2 KPa over 0~20 MHz, a 6-dB angular detection range as large as 70 near 10 MHz, a detection bandwidth larger than 125 MHz, and a stable performance for over twenty minutes without feedback in ambient conditions. Its small form factor, fiber-optic integration, almost omni-directional responsivity and large bandwidth are favorable for in vivo applications and high resolution imaging.

Demonstration of thermo-optic phase shifter by utilizing high-Q resonance in high-index-contrast grating

Jiaxin Lv, Xuefan Yin, Jicheng Jin, Haiyang Zhang, Che Zhao, Chao Peng, and Weiwei Hu

Doc ID: 315179 Received 11 Dec 2017; Accepted 11 Jan 2018; Posted 11 Jan 2018  View: PDF

Abstract: A thermo-optic phase shifter is proposed and demonstrated, by utilizing the high-Q resonance in high-index-contrast grating (HCG). The Q factor up to ~12000 is measured in a footprint of 110μm × 300μm. By heating the HCG with paired metal strip micro-heaters, the optical resonance shifts which induces phase modulation. A phase shift of ~1.2π under heating power of ~32 mW is directly observed and demodulated from the fringes shifting in a Michelson interferometer. The proposed configuration can also be extended to realize high-speed phase shift by adopting electro-optical modulation.

Optical see-through Maxwellian near-to-eye display with enlarged eyebox

Jae-Hyeung Park and Seong Bok Kim

Doc ID: 309473 Received 20 Oct 2017; Accepted 11 Jan 2018; Posted 11 Jan 2018  View: PDF

Abstract: We propose a Maxwellian near-to-eye display implemented using multiplexed holographic optical element. Maxwellian configuration removes the focal cue of the displayed virtual image completely, presenting always-focused image to the observer regardless of the focal length of the eye. The transparent property of the holographic optical element enables the optical see-through feature, making the proposed near-to-eye display suitable for augmented reality applications. The multiplexing of multiple concave mirrors into a single holographic optical element enlarges the effective eyebox, relaxing the limitation of the conventional Maxwellian displays. Optical experiment confirms that the proposed display can present always-focused images on top of the real environment with 9.2º(H)x5.2º(V) field of view, and 9mm(H)x3mm(V) eyebox.

A 40 Gb/s indoor optical wireless system enabled by a cyclically arranged optical beamsteering receiver

Xuebing Zhang, Yu Liu, Zizheng Cao, Fan Li, Zhaohui Li, Rand Ismaeel, Gilberto Brambilla, Yong Chen, and A. Koonen

Doc ID: 314317 Received 28 Nov 2017; Accepted 11 Jan 2018; Posted 11 Jan 2018  View: PDF

Abstract: Indoor optical wireless communication with capability of optical beamsteering attracts lots of attention. One major two dimensional (2D) optical beamsteering scheme is realized by 2D grating or its active counterpart which is usually based on spatial light modulator (SLM). However, there is a fundamental trade-off between field-of-view (FoV) and power efficiency due to the inherent feature of gratings. In this paper, we propose a new class of 2D beamsteering, named cyclically arranged optical beamsteering (CAO-BS) which can break such trade-off. Traditional 2D gratings extend optical beam in Cartesian coordinate (1D grating in horizontal + 1D grating in vertical), while CAO-BS extend optical beam in Polar coordinate (1D grating + angular rotation). Since only 1D grating is engaged, the power efficiency increases with the number of grating lobes reduced. In polar coordinate, the angle rotation tuning in a SLM is quasi-continuous in a range of full 2Pi. The CAO-BS is demonstrated at the receiving end in an indoor experimental system. The FoV is 18° by 360° in polar coordinate without any additional mechanical part. Based on the CAO-BS, 40 Gbit/s On-Off Keying (OOK) data is also successfully transmitted over 1km single mode fibre and 0.5 m free space.

Analytical Model of Waveform-Controlled Single-Cycle Light Pulses from an Undulator

Georgii Shamuilov, Alan Mak, Vitaliy Goryashko, and Peter Salen

Doc ID: 313820 Received 21 Nov 2017; Accepted 11 Jan 2018; Posted 12 Jan 2018  View: PDF

Abstract: This Letter builds upon a recent concept [Z. Tibai et al., Phys. Rev. Lett. 113, 104801 (2014)] for producing ultrashort optical pulses through the coherent radiation of electrons in an undulator. Each pulse contains only a single oscillation cycle, and has a controlled waveform (and hence a stable carrier-envelope phase). While the concept had been demonstrated numerically, this Letter provides an analytical model for the radiation mechanism, thereby revealing three key observations: (i) the correlation between the waveforms of the optical and undulator fields; (ii) the free-space dispersion of transversely confined light; and (iii) the dependence of the optical pulse shape on the undulator field strength.

Adaptive pumping for spectral control of broadband second-harmonic generation

Yanqi Qiao, Yajun Peng, Xianfeng Chen, Yuanlin Zheng, and Fangwei Ye

Doc ID: 314730 Received 01 Dec 2017; Accepted 11 Jan 2018; Posted 12 Jan 2018  View: PDF

Abstract: Second-harmonic generation (SHG) is always a significant frequency conversion process in nonlinear optics for many great applications, but can be limited when broadband spectral laser sources are involved, i.e., femtosecond pulses. The conversion efficiency can be high but the spectral control is hard because of the phase-matching (PM) limitation. Recently, a random quasi-phase-matching (QPM) scheme was proposed to make use of many nonlinear materials with large coefficient but difficult to be phase matched under traditional configurations. The spectral control is even harder in this case and the coherence is completely lost in anisotropic random materials. Here, we proposed an approach to solve this problem, inspired by coherent light control via feedback-based wavefront shaping. We utilized this method for spectral control of broadband SH generation, which is efficient especially in strong scattering media. Randomly selected wavelengths in the broadband spectra were enhanced with a good selectivity and the direction was also controlled in three-dimensional (3D) configuration. This technique paves the way for convenient spatial spectral control of both linear and nonlinear emissions and a local enhancement of the conversion efficiency, indicating a big progress in both random and ultrafast nonlinear optics.

THz-based retrieval of the spectral phase and amplitude of ultrashort laser pulses

massimo petrarca, Alessandro Curcio, Stefano Lupi, and valerio dolci

Doc ID: 312935 Received 13 Nov 2017; Accepted 11 Jan 2018; Posted 12 Jan 2018  View: PDF

Abstract: THz radiation is of great interest for a variety of applications, spanning from particle accelerations, spectroscopy investigations of quantum systems, to high- field study of materials. One of the most common laser-based technique to produce THz pulses is the optical rectification which is a second-order process able to transduce an infrared pump laser to the THz domain (0.1 − 20 THz). In this work we propose and theoretically describe a method to characterize the amplitude and phase of the electric field of the pump laser pulse relying on THz generation and detection. We demonstrate with a numerical example how THz radiation can be used as diagnostics to characterize laser pulses with temporal length at the femtosecond level.

Highly Uniform and Monodisperse β-NaYF4: Sm3+ Nanoparticles for Nanoscale Optical Thermometer

Zhangmei Zhao, FangFang Hu, Zhongmin Cao, Fengfeng Chi, XianTao Wei, Yonghu Chen, Changkui Duan, and Min YIN

Doc ID: 315601 Received 14 Dec 2017; Accepted 11 Jan 2018; Posted 12 Jan 2018  View: PDF

Abstract: Monodisperse β-NaYF4: 1% Sm3+ nanoparticles were fabricated successfully via thermal decomposition technique. Strong temperature dependence of the Sm3+ emission was observed when its thermally populated state 6H7/2 are directly excited to the 4G5/2 level. This strategy not only can eliminate laser heating and background Stokes-type scattering noise, but also has a high quantum yield as a result of one-photon excitation process. Under 594.0 nm laser excitation, the emission intensity of 4G5/2-6H5/2 enhances monotonously with rising temperature from 300 K to 430 K, including physiological temperature range (27 ℃- 60 ℃). The relative temperature sensitivity can reach 1.1 % K-1 and 0.91 % K-1 at 300 K and 330 K, respectively. In addition, the repeatability of temperature sensing was evaluated under several heating-cooling cycles and the decay curves of the emission at 560.0 nm (4G5/2-6H5/2) at different temperatures were also investigated. These results raise the prospects of monodisperse β-NaYF4: 1% Sm3+ nanoparticles for optical temperature sensing in biomedicine fields.

A transmission out of plane interferometer to study thermal distributions in liquids

Manuel De la Torre I., Fernando Mendoza-Santoyo, and Maria Hernandez Montes

Doc ID: 310048 Received 27 Oct 2017; Accepted 11 Jan 2018; Posted 16 Jan 2018  View: PDF

Abstract: An optical set up that does not need to have aligned in-line the object illumination and the camera sensor, or requires a reflection mirror after the sample, is introduced to observe the optical phase in a heating liquid. This system uses an out of plane transmission digital holographic interferometer which uniformly adds speckle to the image holograms by means of a neutral phase screen. The way in which the liquid is illuminated allows having a variable magnification of the observed area of the sample. As a proof of principle a thermal time dependent distribution experiment is presented, whose resulting optical phase readily depicts the temperature time varying distribution in the liquid.

Large-area Rainbow Holographic Diffraction Gratings on Curved Surface Using Transferred Photopolymer Films

Wen-gao Lu, Ru Xiao, Juan Liu, Lei Wang, Haizheng Zhong, and Yongtian Wang

Doc ID: 315123 Received 06 Dec 2017; Accepted 10 Jan 2018; Posted 11 Jan 2018  View: PDF

Abstract: We report the fabrication of large-area holographic diffraction gratings on curved surface from transferred photopolymer films by introducing an water soluble interlayer. The holographic gratings on curved surface have a diffraction efficiency of ~63%, which is ~80% of the recorded holographic film on flat surface. By transferring a recorded holographic grating to a flat substrate, we obtained rainbow holographic gratings under white light illumination. This can be explained by the deformation of the holographic gratings. Our result provides a low-cost method for fabricating diffraction optical elements on curved surface for optical systems.

Ultra-sensitive measurement of gas refractive index using an optical nanofiber coupler

Kaiwei Li, Nan Zhang, MENGYING ZHANG, Guigen Liu, Ting Zhang, and Lei Wei

Doc ID: 313942 Received 21 Nov 2017; Accepted 10 Jan 2018; Posted 11 Jan 2018  View: PDF

Abstract: We report an ultra-sensitive gas refractive index (RI) sensor based on optical nanofiber couplers (ONCs). Theoretical analysis reveals that a dispersion turning point (DTP) exists when the diameter of the coupler is below 1000 nm. Thus, the evanescent field can be greatly enhanced, and the RI sensitivity can be significantly improved to infinity. Then we experimentally demonstrate a DTP and achieve ultrahigh sensitivities of 46470 nm/refractive index unit (RIU) and -45550 nm/RIU around the DTP using a 700 nm-thick ONC. More importantly, the unique twin dips/peaks interference characteristics around the DTP offer further enhancement on the sensitivity to 92020 nm/RIU. The demonstrated sensor not only shows vast potential in ultra-sensitive pressure sensing, acoustic sensing, gas and gas phase biomarkers detection, but also provides a new tool for nonlinear optics, quantum optics, and ultra-cold atom optics.

Photonic hook: A new curved light beam

Liyang Yue, Oleg Minin, Zengbo Wang, James Monks, Alexander Shalin, and Igor Minin

Doc ID: 308158 Received 28 Sep 2017; Accepted 10 Jan 2018; Posted 12 Jan 2018  View: PDF

Abstract: It is well-known that electromagnetic radiation propagates along a straight line, but this common sense was broken by the artificial curved light - Airy beam. In this paper, we demonstrate a new type of curved light beam besides Airy beam, so called ‘photonic hook’. This photonic hook is a curved high-intensity focus by an asymmetric dielectric-cuboid particle illuminated by a plane wave. Difference of the phase velocity and the interference of the waves inside the particle cause the phenomenon of focus bending.

Optical spectral sweep comb liquid flow rate sensor

Yu Shen, Xiaokang Lian, Vishnu Kavungal, Chuan Zhong, Dejun Liu, Yuliya Semenova, Gerald Farrell, Jacques Albert, and John Donegan

Doc ID: 309740 Received 10 Nov 2017; Accepted 10 Jan 2018; Posted 12 Jan 2018  View: PDF

Abstract: In microfluidic chips applications, the flow rate plays an important role. Here we propose a simple liquid flow rate sensor using a tilted fiber Bragg grating (TFBG) as the sensing element. As the liquid flows in the vicinity of TFBG along the fiber axis direction, the TFBG’s spectrum changes due to its contact with water. By comparing the time-swept spectra of the TFBG in water with that of the TFBG with water flowing over it, a spectral sweep comb was formed, and the flow rate can be detected by selecting a suitable sweeping frequency. The proposed sensor has a high Q-value of over 17000 for the lower rate and a large detectable range from 0.0058 mm/s to 3.2 mm/s. And the calculated corresponding lower detectable flow rate of 0.03 nL/s is three orders magnitude better than that of the current fiber flowmeter. Meanwhile, the proposed sensor has the temperature self-compensation function for the variation of the external temperature. We believe that this simple configuration will open a research direction of the TFBG-deriving theory and configuration for lower flow rate measurements for on microfluidic chips applications.

Reducing Rowland ghosts in diffraction gratings by dynamic exposure near-field holography

Dakui Lin, Huoyao Chen, liu zhengkun, Kay Dietrich, Stefanie Kroker, Thomas Käsebier, Ying Liu, Ernst-Bernhard Kley, and Yilin Hong

Doc ID: 310002 Received 27 Oct 2017; Accepted 10 Jan 2018; Posted 12 Jan 2018  View: PDF

Abstract: Near field holography (NFH) with electron beam lithography (EBL)-written phase masks is a promising method for rapid realization of diffraction gratings with high resolution and high accuracy in line density distribution. We demonstrate a dynamic exposure method, in which the grating substrate is shifted during pattern transfer. This reduces the effects of stitching errors resulting in a decreased intensity of optical stray light (i.e. Rowland ghosts). We demonstrate a suppression of ghosts by 60%. This illustrates the potential for dynamic NFH to suppress undesirable periodic patterns from phase masks and alleviate the stitching errors induced by EBL.

Ultralow-threshold continuous-wave lasing assisted by a metallic optofluidic cavity exploiting continuous pump

Hailang Dai, Bei Jiang, Cheng Yin, Zhuangqi Cao, and Xianfeng Chen

Doc ID: 314790 Received 01 Dec 2017; Accepted 10 Jan 2018; Posted 16 Jan 2018  View: PDF

Abstract: We report an ultralow-threshold continuous-wave lasing via a metallic optofluidic resonant cavity based on the symmetrical metal-cladding waveguide (SMCW). The high quality factor Q and spontaneous emission coupling factor of the waveguide strengthen the interaction between the gain medium and the ultrahigh order modes (UOMs), hence the room-temperature, narrow-band lasing can be effectively pumped by a continuous laser of low intensity. Rhodamine 6G and Methylene blue are chosen to verify the applicability of the proposed concept. Lasing is emitted from the chip surface when the pumped laser is well coupled into the UOMs. For Methylene blue with concentration of 2.57*10-13 mol/ml, the operated emission can be observed with the launched pump threshold as low as 2.1 μW/cm2.

Optimized random phase only holograms

Alejandro Velez, Roberto Torroba, and John Fredy Barrera

Doc ID: 313717 Received 16 Nov 2017; Accepted 10 Jan 2018; Posted 10 Jan 2018  View: PDF

Abstract: We propose a simple and efficient technique capable of generating Fourier phase only holograms with a reconstruction quality similar to the results obtained with the Gerchberg-Saxton (G-S) algorithm. Our proposal is to use the traditional G-S algorithm to optimize a random phase pattern for the resolution, pixel size and target size of the general optical system, without any specific amplitude data. This produces an OPtimized RAndom Phase (ORAP), which is used for fast generation of phase only holograms of arbitrary amplitude targets. This ORAP only needs to be generated once for a given optical system, avoiding the need for costly iterative algorithms for each new target. We show numerical and experimental results confirming the validity of the proposal.

Dynamically stable Nd:YAG resonators with beam quality beyond the birefringence limit and pumping of a singly resonant OPO

Niklaus Wetter, Allan Bereczki, and Marcio Lopez

Doc ID: 315539 Received 13 Dec 2017; Accepted 10 Jan 2018; Posted 10 Jan 2018  View: PDF

Abstract: A simple, reliable, linearly-polarized laser source with very high beam quality is demonstrated using standard diode-side-pumped Nd:YAG modules. The laser produced 30 W of output power with beam quality factor M2 < 1.15 over the entire range of input powers and beam quality of 1.02 at the laser operation point. This is, to our knowledge, the highest beam quality for a dynamically stable high-power laser that uses an optically isotropic crystal. The laser was used as a pump source for an optical parametric oscillator based on a periodically poled lithium niobate, producing wavelength in the 1.5-3.8 µm range.

Surface plasmon microscopy by spatial light switching for label-free imaging with enhanced resolution

Taehwang Son, Changhun Lee, Jinwon Seo, In-Hong Choi, and Donghyun Kim

Doc ID: 315803 Received 15 Dec 2017; Accepted 10 Jan 2018; Posted 10 Jan 2018  View: PDF

Abstract: In this report, we describe spatially-switched surface plasmon microscopy (ssSPM) based on two-channel momentum sampling by switched light incidence. The performance evaluated with periodic nanowires in comparison with conventional SPM and bright-field microscopy shows that the resolution of ssSPM is enhanced by almost 15 times over conventional SPM. The results were extended to cell imaging of A549 cell lines. ssSPM provides an extremely simple way to attain diffraction-limit in SPM and to go beyond for super-resolution in label-free microscopy techniques.

Metallic gyroids with broadband circular dichroism

Benjamin Cumming, Gerd Schroeder-Turk, and Min Gu

Doc ID: 317969 Received 19 Dec 2017; Accepted 09 Jan 2018; Posted 10 Jan 2018  View: PDF

Abstract: Circular dichroism is a useful property for filtering or separating beams containing opposite spin angular momentum. Of the many geometries exhibiting circular dichroism, the gyroid micro-structure has proven to be an excellent template for exploring circular dichroism in all three dimensions. However, the bandwidth of the circular dichroism from dielectric gyroids is limited by its narrow circularly polarised stop band. Here we investigate conductive silver gyroid micro-structures using direct laser writing of polymeric templates followed by the electroless deposition of a uniform silver coating. We show that the transformation from dielectric to silver gyroid micro-structure can increase the circular dichroism bandwidth by a factor of 3.

Effective suppression of residual coherent phase error in dual-polarization fiber optic gyroscope

Rongya Luo, Yulin Li, Sheng Deng, Chao Peng, and Li Zhengbin

Doc ID: 313727 Received 17 Nov 2017; Accepted 09 Jan 2018; Posted 10 Jan 2018  View: PDF

Abstract: The impact of residual coherent phase error in a dual-polarization interferometric fiber optic gyroscope (IFOG) is investigated. Although it has been intuitively assumed that the coherence of light source can be eliminated by a sufficient long fiber delay, the experiment and theory indicate that it still contributes a remarkable portion to long-term instability. After the residual coherent phase error being well handled, we demonstrate a dual-polarization IFOG with bias instability of 3.56×10^(-4) º/h. Comparisons show that such performance is even better than the conventional "minimal scheme" that operate in single polarization.

Sub-diffraction multiphoton microscopy with low power continuous wave laser pump

Xiangdong Chen, Shen Li, Bo Du, Yang Dong, Zehao Wang, Guang-can Guo, and Fang-Wen Sun

Doc ID: 314619 Received 29 Nov 2017; Accepted 09 Jan 2018; Posted 10 Jan 2018  View: PDF

Abstract: Multiphoton microscopy (MPM) has been widely used for three-dimensional biological imaging. Here, based on the photon induced charge state conversion process, we demonstrated a low power sub-diffractionMPM with nitrogen vacancy (NV) center in diamond. Continuous wave green and orange lasers were used to pump and detect the two-photon charge state conversion, respectively. With an average laser power of 40 μW, both the axial and lateral resolutions were improved approximately 1.5 times comparing with confocal microscopy. The results can beused to improve the resolution of NV center based quantum sensing and biological imaging.

Spectral asymmetries in the resonance fluorescence of two-level systems under pulsed excitation

Christopher Gustin, Ross Manson, and Stephen Hughes

Doc ID: 312328 Received 06 Nov 2017; Accepted 09 Jan 2018; Posted 09 Jan 2018  View: PDF

Abstract: We present an open-system master equation study of the coherent and incoherent resonance fluorescence spectrum from a two-level quantum system under coherent pulsed excitation. Several pronounced features which differ from the fluorescence under a constant drive are highlighted, including a multi-peak structure and a pronounced off-resonant spectral asymmetry, in stark contrast to the conventional symmetrical Mollow triplet. We also study semiconductor quantum dot systems using a polaron master equation, and show how the key features of dynamic resonance fluorescence change with electron--acoustic-phonon coupling..

Arbitrary shaping of biphoton correlations using near-field frequency-to-time mapping

Hsuan-Hao Lu, Ogaga Odele, Daniel Leaird, and Andrew Weiner

Doc ID: 312524 Received 07 Nov 2017; Accepted 08 Jan 2018; Posted 09 Jan 2018  View: PDF

Abstract: Frequency-to-time mapping (FTM) is a technique used to mirror the spectral shape of an optical waveform in time domain. The regular approach, based on the far-field condition, requires large amounts of dispersion for successful mapping. However, when the far-field condition is insurmountable for achieving a desired temporal profile, another technique, termed near-field FTM, can be employed to assist with the mapping. For the first time, we demonstrate a shaper-assisted near-field FTM using entangled photon pairs. By pre-modifying the two-photon spectral amplitude and phase before propagating the photon pairs through dispersion, we can achieve arbitrary temporal correlations in the near-field region.

Programmable Quantum Random Number Generator without Post-processing

Lac Nguyen, Patrick Rehain, Yong Meng Sua, and Yuping Huang

Doc ID: 312823 Received 06 Nov 2017; Accepted 08 Jan 2018; Posted 09 Jan 2018  View: PDF

Abstract: We demonstrate a viable approach to producing unbiased quantum random numbers whose statistical properties can be arbitrarily programmed, without the need for any post processing such as randomness distillation or distribution transformation. It is based on measuring the arrival time of single photons in shaped temporal modes that are tailored with an electro-optical modulator. We show that quantum random numbers can be created directly in customized probability distributions and pass all randomness tests of the NIST and Dieharder test suites without any randomness extraction. The min-entropies of such generated random numbers are measured close to the theoretical limits, indicating their near-ideal statistics and ultrahigh purity. Easy to implement and arbitrary programmable, this technique can find versatile uses in a multitude of data analysis areas.

Multi-distance diffuse optical spectroscopy with a single optode via hypotrochoidal scanning

Matthew Applegate and Darren Roblyer

Doc ID: 314458 Received 27 Nov 2017; Accepted 08 Jan 2018; Posted 09 Jan 2018  View: PDF

Abstract: Frequency-domain diffuse optical spectroscopy (FD-DOS) is an established technique capable of determining optical properties and chromophore concentrations in biological tissue. Most FD-DOS systems either use manually positioned, handheld probes, or complex arrays of source and detector fibers to acquire data from many tissue locations, allowing for the generation of 2D or 3D maps of tissue. Here, we present a new method to rapidly acquire a wide range of source-detector separations by mechanically scanning a single source-detector pair. The source and detector fibers are mounted on a scan head that traces a hypotrochoidal pattern over the sample which, when coupled with a high-speed FD-DOS system, enables the rapid collection of dozens of SD separations for depth-resolved imaging. We demonstrate that this system has an average error of 4 +/- 2.6% in absorption and 2 +/- 1.8% in scattering across all SD separations. Additionally, by linearly translating the device, the size and location of an absorbing inhomogeneity can be determined through the generation of B-scan images in a manner conceptually analogous to ultrasound imaging. This work demonstrates the potential of single optode diffuse optical scanning for depth resolved visualization of heterogeneous biological tissues at near real-time rates.

Ultrahigh-resolution and wideband optical vector analysis for arbitrary responses

Shifeng Liu, Min Xue, Jianbin Fu, Lugang Wu, and Shilong Pan

Doc ID: 314216 Received 23 Nov 2017; Accepted 08 Jan 2018; Posted 10 Jan 2018  View: PDF

Abstract: An ultrahigh-resolution and wideband optical vector analyzer (OVA) with the simplest architecture, to the best of our knowledge, is proposed and demonstrated based on chirped optical double-sideband (ODSB) modulation in a single-drive Mach-Zehnder modulator (MZM). To distinguish the magnitude and phase information carried by the two sidebands in the ODSB signal, a two-step measurement which biasing respectively the MZM at two different points is applied. Since there is no optical filtering required in the scheme, the optical carrier can be located at any wavelength that is suitable for accurate measurement, for example close to the notch of a notch response or within the passband of a bandpass response, so the proposed OVA has the capability for measuring arbitrary response. An experiment is carried out, which achieves the magnitude and phase responses of a programmable optical processor with bandpass, notch or falling-edge responses. The measurement bandwidth is 134 GHz and the measurement resolution is 1.12 MHz.

Intensity statistics in long random fiber Raman laser

Sergey Vergeles and Leon Ogorodnikov

Doc ID: 313266 Received 13 Nov 2017; Accepted 08 Jan 2018; Posted 08 Jan 2018  View: PDF

Abstract: We study the output emission statistics of random continuous-wave Raman fiber laser. The signal evolution is governed by generalized nonlinear Schr\"{o}dinger equation with inserted gain. The statistics is close to the Rayleigh one, and the deviations are caused by the Kerr nonlinearity. To characterize the deviations, we analytically find mean of the squared output signal intensity basing on the kinetic theory. We show qualitative agreement with available experimental data and supplement the results with numerical calculations. In the limit of small gain the kinetic theory gives finite answer for mean of squared intensity in the first and the second order with respect to small nonlinearity. The result is consistent with the fact that the nonlinear Schr\"{o}dinger equation is integrable in the case of zero gain and is applicable to any generalized NLSE if the inserted terms are effectively small.

Intense broadband mid-infrared pulses for supercontinuum generation in gaseous medium

Ya Bai, ChangJie Cheng, Xiaolu Li, Peng Liu, Ruxin Li, and Zhizhan Xu

Doc ID: 313861 Received 20 Nov 2017; Accepted 08 Jan 2018; Posted 08 Jan 2018  View: PDF

Abstract: We produce the extremely bright mid-infrared (mid-IR) pulses with a tunable wavelength of 7 - 15 μm through difference frequency generation. Optimization of beam quality and beam focus results in an intense mid-IR pulse that spatio-temporally confined in the lambda-cubic volume. Near planar wavefront is achieved through the pump wavefront curvature manipulation in three-wave mixing process. As a result, mid-IR pulses with the peak fields up to 280 MV/cm and the intensities exceeding 100 TW/cm2 are produced at 10 μm wavelength. Interaction of such an intense mid-IR field with Xe and Kr gas forms plasma and generates supercontinuum visible spectrum.

Long-distance thermal temporal ghost imaging over optical fibers

Xin Yao, Wei Zhang, Hao Li, Lixing YOU, Zhen Wang, and Yidong Huang

Doc ID: 314137 Received 22 Nov 2017; Accepted 08 Jan 2018; Posted 08 Jan 2018  View: PDF

Abstract: A thermal ghost imaging scheme between two distant parties is proposed and experimentally demonstrated over long-distance optical fibers. In the scheme, the weak thermal light is split into two paths. Photons in one path are spatially diffused according to their frequency by a spatial dispersion component, then illuminate the object and record its spatial transmission information. Photons in the other path are temporally diffused by a temporal dispersion component. By the coincidence measurement between photons of the two paths, the object can be imaged in a way of ghost imaging, based on the frequency correlation between the photons in the two paths. In the experiment, the weak thermal light source is prepared by the spontaneous four-wave mixing in a silicon waveguide. The temporal dispersion is introduced by single mode fibers of 50km, which also could be looked as a fiber link. Experiment results show that this scheme can be realized over long-distance optical fibers.

Sensitive measurement of stress birefringence of fused silica substrates with cavity ring-down technique

Xiao Shilei, Bincheng Li, Hao Cui, and Jing Wang

Doc ID: 314437 Received 27 Nov 2017; Accepted 08 Jan 2018; Posted 17 Jan 2018  View: PDF

Abstract: Polarized cavity ring-down technique was employed to measure precisely the residual stress birefringence of fused silica substrates with greatly enhanced measurement sensitivity. Intracavity birefringence resulted in beating of two orthogonally resonant modes in a Fabry-Perot cavity. The beating frequency of the ring-down decay was directly related to phase retardation induced by stress birefringence of optical components inside the cavity. For fused silica substrates, measurement reproducibilities of phase retardation of 2.38×10-6 rad and of optical path difference of 2.4×10-4 nm were experimentally achieved. In addition, spatially-resolved mapping of stress birefringence of a fused silica substrate was obtained, which was in good agreement with that measured with a commercial stress birefringence measurement instrument. The experimental results demonstrated that cavity ring-down is a sensitive technique for stress birefringence measurements of optical components.

Terahertz nonreciprocal isolator based on magneto-optical microstructure at room temperature

Fei Fan, Chuan-Zhong Xiong, Jie -Rong Cheng, and Shengjiang Chang

Doc ID: 315222 Received 08 Dec 2017; Accepted 08 Jan 2018; Posted 10 Jan 2018  View: PDF

Abstract: We investigated THz nonreciprocal circularly polarized transmission in the thin longitudinally magnetized InSb film, especially its non-eigen nonreciprocal transmission mechanism working at room temperature. Then based on this effect, we presented a THz isolator for linear polarized waves, in which nonreciprocal transmission of the InSb film is converted and enhanced by a pair of orthogonal artificial birefringence gratings. After the optimization, the isolation reaches 24dB and insertion loss is less than 0.5dB working at room temperature and low magnetic field.

Fourier Transform Spectroscopy by Repetition Rate Sweeping of a Single Electro-Optic Frequency Comb

Md Imrul Kayes and Martin Rochette

Doc ID: 313566 Received 16 Nov 2017; Accepted 07 Jan 2018; Posted 16 Jan 2018  View: PDF

Abstract: We demonstrate the operation of a Fourier transform spectrometer that operates from sweeping the pulse repetition frequency of an electro-optic frequency comb. Incorporating a length imbalanced interferometer, this single comb system is analogous to a conventional dual comb system, but with a greatly simplified design. The functionality of the spectrometer is demonstrated via the high-resolution spectrum measurement of an H13C14N reference gas cell.

Few-period helically-twisted all-solid photonic bandgap fibers

Jie Li, Pengcheng Fan, Li-Peng Sun, Chuang Wu, and Bai-Ou Guan

Doc ID: 309149 Received 12 Oct 2017; Accepted 07 Jan 2018; Posted 08 Jan 2018  View: PDF

Abstract: We demonstrate a kind of few-period helically-twisted all-solid photonic bandgap fibers (AS-PBGFs). The helical structure leads to orbital resonance of the cladding rod mode, which couples with the core mode. A two-period twist structure exhibits an extremely strong resonant dip of up to 30 dB. A series of samples with twist periods of 3.31 – 7.92 mm (yielding helical rates of 1.90 – 0.79 rad*mm^-1) in association with different resonance orders are fabricated and demonstrated. The inherent physical mechanism underlying the resonance is analyzed. Moreover, the responses of the resonance to mechanical torsion, strain, and temperature are investigated in detail. The twisted AS-PBGFs are featured with high reproducibility, stability, and robustness and have great potential in tunable in-fiber filters and sensors.

3D thickness map reconstruction of dielectric thin films using scattering of surface plasmon polaritons

Cesar Garcia-Ortiz, Roldolfo Cortes, Robin Orejel, Raul Hernandez-Aranda, Israel Martinez-Lopez, J. Aguilar, and Victor Coello Cardenas

Doc ID: 315583 Received 12 Dec 2017; Accepted 07 Jan 2018; Posted 09 Jan 2018  View: PDF

Abstract: Thin films are key elements in current developments of nanotechnology, and its characterization has become an essential task. In this work, we report on a technique to reconstruct full 3D maps of dielectric thin films using the scattered light of decoupled surface plasmon polaritons. Patterned magnesium fluoride thin films were fabricated and their 3D thickness map was fully reconstructed with high (<1 nm) precision. This technique can be applied and easily adjusted to identify inhomogeneities in wide areas (mm^2 – cm^2) of dielectric samples with subnanometer precision, or to characterize the fabrication processes involved in the preparation of patterned multilayered systems.

Highly Sensitive Selectively Coated Photonic Crystal Fiber Based Plasmonic Sensor

Rifat Ahmmed Aoni, Firoz Haider, Rajib Ahmed, Ghafour Mahdiraji, FRM Adikan, and Andrey Miroshnichenko

Doc ID: 313363 Received 08 Dec 2017; Accepted 06 Jan 2018; Posted 10 Jan 2018  View: PDF

Abstract: Extremely sensitive and compact sensor structure which able to detect the real-time sample/analyte is highly desirable. In this work, we propose a highly sensitive plasmonic sensing scheme with the well-known miniaturized photonic crystal fiber (PCF) attributes. A large cavity is introduced in the first ring of the PCF’s for the efficient field excitation of the surface plasmon polariton (SPP) mode and proficient infiltration of the sensing elements. Due to irregular air-holes diameter in the 1st ring, it exhibits the birefringence behavior which enhance the sensing performance. The novel plasmonic material gold has been used considering the chemical stability in aqueous environment. The guiding properties and the effects of the sensing performance with different parameters have been investigated by finite element method (FEM), and fabricated the proposed PCF’s using stack-and-draw fiber drawing method. The proposed sensor performance investigated based on the wavelength and amplitude sensing techniques, and shows the maximum sensitivities of 11,000 nm/RIU and 1,420 RIU-1, respectively. It also shows the maximum sensor resolution of 9.1×10-6 and 7×10-6 RIU for the wavelength and amplitude sensing schemes. The proposed amplitude sensitivity and sensor resolution is highest among the reported PCF SPR sensors, to the best of our knowledge. It also shows the maximum figure of merits (FOM) of 407. Furthermore, the proposed sensor is able to detect the analyte refractive indices in the range of 1.33 to 1.42, as a result it will find the possible applications in the medical diagnostics, biomolecules, organic chemical and chemical analytes detection.

High-order super-resolution optical fluctuation imaging based on low-pass denoising

Limin Zou, Su Zhang, Baokai Wang, and Jiubin Tan

Doc ID: 309397 Received 18 Oct 2017; Accepted 06 Jan 2018; Posted 08 Jan 2018  View: PDF

Abstract: A new scheme of Super-resolution Optical Fluctuation Imaging (SOFI) is proposed to broaden its application in high-order case, by separating the elimination of shot noise from the computation of cumulant, applying the low-pass denoising operator to SOFI (LPD-SOFI). The high-order cumulants are derived from a basic recursion of moments with the suppression of shot noise by the low-pass denoising on raw data. A 10.6-fold lateral resolution enhancement with the cumulant order of 16th and a 7-fold 3D resolution enhancement with the cumulant order of 10th are experimentally demonstrated. LPD-SOFI therefore holds great promise and potential for broad applications in super-resolution 3D imaging.

Atom-resonant squeezed light from a tunable monolithic ppRKTP parametric amplifier

Joanna Zielinska and Morgan Mitchell

Doc ID: 313730 Received 21 Nov 2017; Accepted 05 Jan 2018; Posted 05 Jan 2018  View: PDF

Abstract: We demonstrate vacuum squeezing at the D1 line of atomic rubidium (795 nm) with a tunable, doubly-resonant, monolithic sub-threshold optical parametric oscillator in periodically-poled Rb-doped potassium titanyl phosphate. The squeezing appears to be undiminished by a strong dispersive optical nonlinearity recently observed in this material.

Coherent-perfect-absorber and laser for bound states in continuum

Bikashkali Midya and Vladimir Konotop

Doc ID: 309167 Received 16 Oct 2017; Accepted 05 Jan 2018; Posted 05 Jan 2018  View: PDF

Abstract: It is shown that two fundamentally different phenomena, the bound states in continuum and the spectral singularity (or time-reversed spectral singularity), can occur simultaneously. This can be achieved, in particular, in a rectangular core dielectric waveguide with embedded active (or absorbing) layer. The idea can be used for experimental implementation of a laser or a coherent-perfect-absorber for photonic bound state that resides in continuous spectrum.

Time-multiplexed Light Field Synthesis via Factored Wigner Distribution Function

Stephen Hamann, Liang Shi, Olav Solgaard, and Gordon Wetzstein

Doc ID: 312874 Received 06 Nov 2017; Accepted 04 Jan 2018; Posted 04 Jan 2018  View: PDF

Abstract: An optimization algorithm for preparing display-ready holographic elements (hogels) to synthesize a light field is outlined, and proof of concept is experimentally demonstrated. This method allows for higher-rank factorization, which can be used for time-multiplexing multiple frames for improved image quality, using phase-only and fully complex modulation with a single spatial light modulator.

Self-assembled monolayers of bimetallic Au/Ag nanospheres with superior SERS activity for ultra-sensitive triphenylmethane dyes detection

Yue Tian, Hua Zhang, Linlin Xu, Ming Chen, and Feng Chen

Doc ID: 313431 Received 15 Nov 2017; Accepted 04 Jan 2018; Posted 05 Jan 2018  View: PDF

Abstract: The bimetallic Au/Ag self-assembled monolayers (SAMs) were constructed by using mono-dispersed Au/Ag nanospheres (Ag: 4.07%~34.53%) via evaporation-based assembly strategy. The composition-dependent surface-enhanced Raman scattering (SERS) spectroscopy revealed that the Au/Ag (Ag: 16.83%) SAMs provide maximized activity for triphenylmethane (TPM) dyes detection. With the inter-metallic synergy, the optimized SAMs enable the Raman intensity of crystal violet (CV) molecules to be about 260 times higher than that of monometallic Au SAMs. Moreover, the SERS signals with excellent uniformity (<5% variation) are sensitive down to 10-13M concentrations because of the optimal matching between bimetallic plasmon resonance and the incident laser wavelength. It is extremely suitable for ultra-trace detections in environmental surveillance and food safety supervision.

Compact burst-mode Nd:YAG laser for velocity and species measurements at 100 kHz in turbulent flows

Michael Smyser, Kazi Arafat Rahman, Mikhail Slipchenko, Sukesh Roy, and Terrence Meyer

Doc ID: 314489 Received 28 Nov 2017; Accepted 04 Jan 2018; Posted 08 Jan 2018  View: PDF

Abstract: A compact-footprint (<0.2 m²) flash-lamp-pumped, burst-mode Nd:YAG-based master-oscillator pulsed-amplifier (MOPA) laser is reported with a fundamental 1064 nm output of over 14 J per burst. A directly modulated diode laser seed source is used to generate 10 ms duration, arbitrary sequences of 100 kHz doublet or singlet pulses for planar velocimetry or speciation, respectively. Flexible pulse widths are used to balance the energy distribution of pulse doublets and achieve second harmonic conversion efficiency up to 42%. Burst-mode laser performance characteristics, results of planar measurements, and potential applications in turbulent reacting and non-reacting flows are discussed.

Kerr lens modelocked Yb:CALGO thin-disk laser

Norbert Modsching, Clement Paradis, François Labaye, Maxim Gaponenko, Ivan Graumann, Andreas Diebold, Florian Emaury, Valentin Wittwer, and Thomas Südmeyer

Doc ID: 313214 Received 16 Nov 2017; Accepted 04 Jan 2018; Posted 08 Jan 2018  View: PDF

Abstract: We demonstrate the first Kerr lens modelocked Yb:CaGdAlO4 (Yb:CALGO) thin-disk laser oscillator. It generates pulses with a duration of 30 fs at a center wavelength of 1047 nm and a repetition rate of 124 MHz. The laser emits the shortest pulses generated by a thin-disk laser oscillator, equal to the shortest pulse duration obtained by Yb-doped bulk oscillators. The average output power is currently limited to 150 mW by the low gain and limited disk quality. We expect that more suitable Yb:CALGO disks will enable substantially higher power levels with similar pulse durations.

Single-Mode Ultraviolet Whispering Gallery Mode Lasing from a Floating GaN Microdisk

Gangyi Zhu, jiaping LI, Jitao lI, Jiyuan Guo, Jun Dai, Chunxiang XU, and yongjin wang

Doc ID: 312554 Received 06 Nov 2017; Accepted 03 Jan 2018; Posted 09 Jan 2018  View: PDF

Abstract: We fabricated a floating GaN microdisk supported by silicon pillar through photolithography, dry etching GaN, and isotropic wet-etching silicon methods. Single-mode ultraviolet whispering gallery mode (WGM) lasing was obtained from the floating GaN microdisk under optical pumping conditions at room temperature. The features of WGM lasing, i.e., the threshold, emission intensity, and lasing mode number, were characterized. A two-dimensional finite-difference time-domain simulation about the optical field contour profile also confirmed the resonance mechanism of WGM lasing. This work can help realize single-mode WGM lasing with high quality factor and low threshold.

Performance enhancement using a stable low-pretilt molecular configuration and a novel driving method for optically compensated bend liquid crystal devices

Guan-Jhong Lin, Tien-Jung Chen, Jhao-Ting Wu, and Jin-Jei Wu

Doc ID: 312871 Received 07 Nov 2017; Accepted 03 Jan 2018; Posted 04 Jan 2018  View: PDF

Abstract: A stable low-pretilt molecular configuration (SLPMC) is successfully developed in optically compensated bend (OCB) liquid crystal (LC) devices by simultaneously employing the curing voltage and surface-anchored crosslinking monomer during the polymerization process. For the SLPMC OCB cell with the low-bend state, the warm-up voltage making the LC molecules reorient from the splay to the bend state is annihilated, and the transient twist state occurring as the driven LC molecules recover from the bend to the splay state is also eliminated. In addition, with the novel driving method selecting the specific driving point, the proposed SLPMC OCB cell not only exhibits a good response performance, but also outputs a higher light transmittance, which is superior to the conventional OCB and no-bias-bend cells. This paper demonstrates an effective SLPMC fabrication method, and points out the significant contributions of SLPMC on the electro-optical properties, which will benefit and enhance the performance design in the OCB-based applications.

Refractive Index Sensor Based on Graphene-Coated Photonic Surface Wave Resonance

Qianru Yang, linling qin, Guoyang Cao, Cheng Zhang, and Xiaofeng Li

Doc ID: 312983 Received 08 Nov 2017; Accepted 03 Jan 2018; Posted 05 Jan 2018  View: PDF

Abstract: We propose a graphene-coated photonic system with the excitation of Bloch surface waves (BSWs) for refractive index sensing. Through manipulating the BSW resonance in the truncated photonic crystal under Kretschmann configuration, the absorption in a graphene monolayer is significantly enhanced assisted by the strong electromagnetic confinement of BSWs. The sharp and low reflectivity dip and the strong wave-environment interaction enable the highly sensitive optical sensing. First-order perturbation theory and transfer-matrix calculation indicate that the system sensitivity is strongly related to the ratio of the electric field energy in the detection area, operation wavelength, and incident angle. Study shows that the wavelength sensitivity and figure-of-merit (FOM) of the optimized system can reach 70 nm/RIU and 196.44, respectively. More generalized BSW system configurations, e.g., aperiodic BSW design, are proposed for the refractive index sensing application.

Third-harmonic generation and scattering in combustion flames using femtosecond laser filament

Hong-Wei Zang, He-long Li, Yue Su, Yao Fu, Mengyao Hou, Andrius Baltuska, Kaoru Yamanouchi, and Huailiang Xu

Doc ID: 313288 Received 13 Nov 2017; Accepted 03 Jan 2018; Posted 05 Jan 2018  View: PDF

Abstract: The coherent radiations in the ultraviolent (UV) range have high potential applicability to the diagnosis of the formation processes of soot in combustion because of the high scattering efficiency in the UV wavelength region even though the UV light is lost largely by the absorption within the combustion flames. We show that the third harmonic (TH) of a Ti: Sapphire 800 nm femtosecond laser is generated in a laser-induced filament in a combustion flame and that the conversion efficiency of the TH varies sensitively by the ellipticity of the drive laser pulse, but does not vary so much by the choice of alkanol species introduced as fuel for the combustion frames. We also find that the TH recorded from the side direction of the filament is the Rayleigh scattering of the TH by soot nanoparticles within the flame and that the intensity of the TH varies dependent on the fuel species as well as on the position of the laser filament within the flame. Our results show that a remote and in-situ measurement of distributions of soot nanoparticles in a combustion flame can be achieved by the Rayleigh scattering spectroscopy of the TH generated by a femtosecond-laser induced filament in the combustion flame.

High energy thermoelectrically cooled Fe:ZnSe laser tunable over 3.75-4.82 µm

Vladimir Kozlovsky, Michael Frolov, Yuri Korostelin, Yan Skasyrsky, and Yuri Podmar'kov

Doc ID: 313826 Received 20 Nov 2017; Accepted 03 Jan 2018; Posted 04 Jan 2018  View: PDF

Abstract: The characteristics of a thermoelectrically cooled to 220 K Fe:ZnSe laser are described. Output energy of 7.5 J and optical-to-optical efficiency of 30% have been demonstrated in single-shot operation at 4.3 μm with a 2.94-μm Er:YAG pump laser. By means of using intracavity prism, continuous tuning from 3.75 to 4.82 μm has been obtained at output energy up to 3.1 J.

Continuous-wave operation in directly patterned perovskite distributed feedback light source at room temperature

Abouzar Gharajeh, Ross Haroldson, Zhitong Li, Jiyoung Moon, Balasubramaniam Balachandran, Walter Hu, Anvar Zakhidov, and Qing Gu

Doc ID: 310051 Received 27 Oct 2017; Accepted 03 Jan 2018; Posted 04 Jan 2018  View: PDF

Abstract: We report a directly patterned perovskite distributed feedback (DFB) resonator, and show narrow amplified spontaneous emission (ASE) at pump powers as low as 0.1W/cm2, under continuous-wave (CW) optically pumping condition at room temperature. Compared to the pristine thin film photoluminescence spectrum, a 16-fold reduction in emission linewidth in the MAPbI3 DFB cavity was observed. The direct nanostructuring of perovskites was achieved by thermal nanoimprint lithography. Our findings pave the way towards realizing CW pumped perovskite lasers at room temperature and energy-efficient perovskite light sources.

Terahertz ptychography

Lorenzo Valzania, Thomas Feurer, Peter Zolliker, and Erwin Hack

Doc ID: 314189 Received 24 Nov 2017; Accepted 02 Jan 2018; Posted 03 Jan 2018  View: PDF

Abstract: We realized a phase retrieval technique using THz radiation as an alternative to THz digital holography, named THz ptychography. Ptychography has been used in X-ray imaging as a groundbreaking improvement of conventional coherent diffraction imaging. Here we show that ptychography can be performed at THz frequencies too. We reconstructed an amplitude and a phase object with both simulated and real data. Lateral resolution accounts to < 2λ, while depth variations as low as λ/30 can be assessed.

High speed waveguide photodetector for 64 Gbaud coherent receiver

Young-Ho Ko, Joong-Seon Choe, Won-Seok Han, Seo young Lee, Young-Tak Han, Hyun-Do Jung, Chun Ju Youn, Jong-Hoi Kim, and Yongsoon Baek

Doc ID: 314123 Received 28 Nov 2017; Accepted 02 Jan 2018; Posted 05 Jan 2018  View: PDF

Abstract: A high-speed waveguide photodetector has been successfully fabricated for an integrated coherent receiver. Dual laterally tapered structures are introduced for a spot-size converter. We optimize the responsivity and the polarization-dependent loss of the spot-size converter-integrated waveguide photodetector through the beam propagation method simulation. The waveguide photodetector is designed with electrical as well as optical optimizations. The photodetector provides sufficient alignment tolerance, high responsivity of 0.73 A/W, and low polarization-dependent loss of 0.27 dB, which is good agreement with the simulation results. By increasing the thickness of the matching layer and the n-doped upper taper, the electrical properties of the photodetector are enhanced. The photodetector has a 3 dB bandwidth of 45 GHz, providing high-speed operation. Through the electrical and optical optimizations, we successfully obtain the high-speed waveguide photodetector for a 64 Gbaud integrated coherent receiver.

Simultaneous frequency up-conversion and phase-coding of a radio frequency signal for photonic radars

Sha Zhu, Zhan Shi, Ming Li, Ninghua Zhu, and Wei Li

Doc ID: 314597 Received 29 Nov 2017; Accepted 02 Jan 2018; Posted 05 Jan 2018  View: PDF

Abstract: We report a photonic approach to simultaneously realize frequency upconversion and phase-coding of a radio-frequency (RF) signal based on polarization manipulating of optical signals. An intermediate frequency (IF) signal is up-converted to the local frequency (LO) band using a dual-polarization dual-parallel Mach-Zehnder modulator (DP-DPMZM), while a high-speed polarization modulator (PolM) is used to realize high-speed phase-coding of the up-converted signal. The key advantage of the proposed method is that no optical or electrical filters are required to remove the residual IF, LO, and undesired down-converted signals, which ensures a broad operation bandwidth, excellent isolation, and wide tunability. The proposed scheme is theoretically analyzed and experimentally verified.

Counter-rotating cavity solitons in a silicon nitride microresonator

Chaitanya Joshi, Alexander Klenner, Yoshitomo Okawachi, Mengjie Yu, Kevin Luke, Xingchen Ji, Michal Lipson, and Alexander Gaeta

Doc ID: 313297 Received 13 Nov 2017; Accepted 01 Jan 2018; Posted 03 Jan 2018  View: PDF

Abstract: We demonstrate the generation of counter-rotating cavity solitons in a silicon nitride microresonator using a fixed, single-frequency laser. We demonstrate a dual 3-soliton state with a difference in the repetition rates of the soliton trains that can be tuned by varying the ratio of pump powers in the two directions. Such a system enables a highly compact, tunable dual comb source that can be used for applications such as spectroscopy and distance ranging.

nBn extended short–wavelength infrared focal plane array

Arash Dehzangi, Abbas Haddadi, Romain Chevallier, Yiyun Zhang, and Manijeh Razeghi

Doc ID: 314320 Received 01 Dec 2017; Accepted 01 Jan 2018; Posted 04 Jan 2018  View: PDF

Abstract: An extended short–wavelength nBn InAs/GaSb/AlSb type–II superlattice–based infrared focal plane array imager was demonstrated. A newly developed InAs0.10Sb0.90/GaSb superlattice design was used as the large–bandgap electron–barrier in this photodetector. The large band gap electron–barrier design in this nBn photodetector architecture leads to the device having lower dark current densities. A new bi–layer etch–stop scheme using a combination of InAs0.91Sb0.09 bulk and AlAs0.1Sb0.9/GaSb superlattice layers was introduced to allow more complete substrate removal and a shorter wavelength cut-on. Test pixels exhibit 100% cut–off wavelengths of ~2.30 and ~2.48 μm at 150 and 300 K, respectively. The devices achieve saturated quantum efficiency values of 59.7% and 63.8% at 150 and 300 K, respectively, under back–side illumination and without any anti-reflection coating. The large band gap electron–barrier design in nBn photodetector architecture leads the device to operate with lower dark current densities. At 150 K, the photodetectors exhibit dark current density of 8.75×10-8 A/cm2 under −400 mV applied bias providing a specific detectivity of 2.82×1012 cm•Hz1/2/W at 1.78 μm. At 300 K, the dark current density reaches 4.75×10-2 A/cm2 under -200 mV bias, providing a specific detectivity of 8.55×109 cm•Hz1/2/W 1.78 μm.

Metamaterial Engineered Transparency due to nullifying of multipole moments

Alexey Basharin, Anar Ospanova, and Alina Karabchevsky

Doc ID: 313654 Received 16 Nov 2017; Accepted 30 Dec 2017; Posted 02 Jan 2018  View: PDF

Abstract: Here, we propose novel transparency effect in cylindrical all-dielectric metamaterials. We show that cancellation of multipole moments of the same kind lead to almost zero radiation losses in all-dielectric metamaterials due to the counter-directed multipolar moments in metamolecule. Nullifying of multipoles, mainly dipoles and suppression of higher multipoles results in ideal transmission of incident wave through the designed metamaterial. The observed effect could pave the road to new generation of light-manipulating transparent metadevices such as filters, waveguides, cloaks and more.

Devising genuine twisted cross-spectral densities

Franco Gori and Massimo Santarsiero

Doc ID: 315050 Received 07 Dec 2017; Accepted 30 Dec 2017; Posted 05 Jan 2018  View: PDF

Abstract: Sticking a twist to a partially coherent source cannot be done at will since the result can violate the definiteness property of the corresponding cross-spectral density. As a matter of fact, the study of twisted sources has been mainly concentrated on the original case proposed by Simon and Mukunda [J. Opt. Soc. Am. A 10, 95 (1993)] of circularly symmetric Gaussian Schell-model sources. Here, we discuss a modeling procedure that can be used to generate numberless genuine twisted sources without symmetry constraints. As geometrically simple examples, two cases of non-Gaussian twisted sources endowed with circular or rectangular symmetry are worked out explicitly.

Dependence of Quality Factor on Surface Roughness in Crystalline Whispering-Gallery Mode Resonators

Guoping Lin, Rémi HENRIET, Aurelien Coillet, Maxime Jacquot, Luca Furfaro, Gilles Cibiel, Laurent Larger, and Yanne Chembo

Doc ID: 312430 Received 31 Oct 2017; Accepted 29 Dec 2017; Posted 02 Jan 2018  View: PDF

Abstract: We present an experimental study of the variation of quality factor of WGM resonators as a function of surface roughness. We consider mm-size whispering-gallery mode resonators manufactured with fluoride crystals, featuring quality factors of the order of one billion at 1550 nm. The experimental procedure consists in repeated polishing steps after which the surface roughness is evaluated using profilometry by white light phase-shifting interferometry, while the quality factors are determined using the cavity-ring down method. This protocol permits to establish an explicit curve linking the quality factor of the disk-resonator to the surface roughness of the rim. We have performed measurements with four different crystals, namely magnesium, calcium, strontium and lithium fluoride. We have thereby found that the variations of quality factor as a function of surface roughness is universal, in the sense that it is globally independent of the bulk material under consideration. We discuss as well our experimental results in the light of some theoretical estimates of surface scattering quality factors already published in the literature.

Splitting an optical vortex beam to study photonicorbit-orbit interactions

Claire Cisowski and Ricardo Correia

Doc ID: 314313 Received 27 Nov 2017; Accepted 29 Dec 2017; Posted 02 Jan 2018  View: PDF

Abstract: We numerically and experimentally evidence photonicorbit-orbit interactions in freely propagating asymmetricalbeams carrying orbital angular momentum. AFresnel biprism is used to carry out the wavefront divisionof an optical vortex beam, generating two complementaryasymmetrical beams. We evidence the opticalorbital-Hall effect in the form angular deviationsfrom the beam´s geometrical expectation and also observethe parallel transport of the beam structure alongthe ray, manifesting as the rotation of the field transversedistribution.

Active frequency matching in stimulated Brillouin amplification for production of 2.4 J 200 ps laser pulse

hang yuan, yulei wang, Zhiwei Lu, and Zhenxing Zheng

Doc ID: 314507 Received 28 Nov 2017; Accepted 29 Dec 2017; Posted 02 Jan 2018  View: PDF

Abstract: A frequency matching Brillouin amplification in high power solid-state laser systems is proposed. The energy extraction efficiency could be maintained at a high level in a non-collinear Brillouin amplification structure using an exact Stokes frequency shift. Laser pulses having a width of 200 ps and energy of 2.4 J were produced. This method can be used to transfer energy from a long pulse to a short pulse through a high power solid-state laser system.

On-Chip Optical Transduction Scheme for Graphene Nano-Electro-Mechanical Systems in Silicon-Photonic Platform

Aneesh Dash, Shankar Kumar Selvaraja, and Akshay Naik

Doc ID: 312371 Received 08 Nov 2017; Accepted 28 Dec 2017; Posted 04 Jan 2018  View: PDF

Abstract: We present a scheme for on-chip optical transduction of strain and displacement of Graphene-based Nano-Electro-Mechanical Systems (NEMS). A detailed numerical study on the feasibility of three silicon-photonic integrated circuit configurations is presented: Mach-Zehnder Interferometer(MZI), micro-ring resonator and ring-loaded MZI. An index-sensing based technique using a Mach-Zehnder Interferometer loaded with a ring resonator with a moderate Q-factor of 2400 can yield a sensitivity of 28 fm/√Hz, and 6.5 × 10¯⁶ %/√Hz for displacement and strain respectively. Though any phase sensitive integrated photonic device could be used for optical transduction, here we show a maximum sensitivity is achievable by combining resonance with phase sensitivity.

Shot-noise-limited Doppler-broadened noise-immune cavity-enhanced optical heterodyne molecular spectrometry

Gang Zhao, Thomas Hausmaninger, Weiguang Ma, and Ove Axner

Doc ID: 314714 Received 30 Nov 2017; Accepted 28 Dec 2017; Posted 10 Jan 2018  View: PDF

Abstract: Shot-noise-limited Doppler broadened (Db) noise-immune cavity-enhanced optical heterodyne molecular spectrometry (NICE-OHMS) has been realized by implementation of balanced detection. A characterization of the system based on Allan-Werle plots of the absorption coefficient retrieved by fitting a model function to data shows that the system has a white noise equivalent absorption per unit length (WNEAL) of 2.3×10(-13) cm(-1) Hz(-1/2), solely 44 % above the shot-noise limit, and a detection sensitivity of 2.2×10(-14) cm(-1) over 200 s, both being unprecedented for Db NICE-OHMS. The WNEAL follows the expected inverse square root dependence on power that is representative of a shot-noise limited response, which confirms that the system is shot-noise-limited.

Compact assembly-free vector bend sensor based on all-in-fiber-core Mach-Zehnder interferometer

Pengcheng Chen, Xuewen Shu, and Kate Sugden

Doc ID: 312956 Received 07 Nov 2017; Accepted 27 Dec 2017; Posted 03 Jan 2018  View: PDF

Abstract: A novel low-cost, compact, assembly-free and sensitive optical fiber curvature sensor is presented. This device consists of an off-axis positive refractive index modified zone (PRIMZ), induced by direct femtosecond laser, written in single mode fiber (SMF) core. The PRIMZ transforms the original SMF section into a few-mode fiber (FMF). As a result, the whole fiber forms an assembly-free “SMF-FMF-SMF” sandwich Mach-Zehnder interferometer. When the device is bent, a direction-dependent spectral shift of the interference pattern is produced. The sensitivity of the sensor is up to 2.53 and 2.24nm/m-1 for the 0° and 180° orientations in a wide bend range (from 0-4m-1). In addition, the device is immune to surrounding refractive index and has low temperature crosstalk, which make it very attractive for practical structural monitoring applications.

Raman fiber laser with random distributed feedback based on a twin-core fiber

Budarnykh Artem, Ivan Lobach, Ekaterina Zlobina, Vladimir Vel'miskin, Sergey Kablukov, Sergey Semjonov, and Sergey Babin

Doc ID: 306577 Received 06 Sep 2017; Accepted 27 Dec 2017; Posted 04 Jan 2018  View: PDF

Abstract: An operation of a linearly-polarized Raman fiber laser with random distributed feedback based on a polarization-maintaining twin-core fiber is demonstrated for the first time. The results indicate that the twin-core fiber allows one to obtain laser generation with linewidth of about five times smaller than that for the random laser based on conventional fiber with similar parameters. The reasons of narrowing include both the weakening of nonlinear effects due to the power density reduction, and the spectrally selective properties of the twin-core fiber.

The abnormal nonlinear optical properties of hybrid graphene-TiO2 nanostructures

Yongqiang Jiang, Ying Ma, Zhaoyang Fan, Peng Wang, Xiaohong Li, Yingwei Wang, Yu Zhang, Jianqiang Shen, Gang Wang, Zhong-Jian Yang, Si Xiao, Yongli Gao, and jun He

Doc ID: 313480 Received 16 Nov 2017; Accepted 27 Dec 2017; Posted 03 Jan 2018  View: PDF

Abstract: The nonlinear optical (NLO) properties of graphene-TiO2 nanoparticle composite (GNP) and graphene-TiO2 nanowire composite (GNW) are investigated by the spatial self-phase modulation (SSPM) and Z-scan. The SSPM results of GNP and GNW show that they possess strong self-diffraction effects at 1100 nm and no signal at 700 nm, which is different from all previous reports of other two-dimensional materials. A possible mechanism is that NLO behaviors are dominated by TiO2 at visible wavelength, while by graphene at near infrared wavelength, respectively. The Z-scan results of GNP and GNW show reverse saturable absorption at 700 nm, but saturable absorption at 1100 nm. Our results demonstrate that, by choosing appropriate coupling, we could design two-dimensional materials that have specific nonlinear optical properties at particular wavelengths.

Bioresorbable optical fiber Bragg gratings

Diego Pugliese, Maria Konstantaki, Ioannis Konidakis, Edoardo Ceci Ginistrelli, Nadia Boetti, Daniel Milanese, and Stavros Pissadakis

Doc ID: 314645 Received 29 Nov 2017; Accepted 27 Dec 2017; Posted 03 Jan 2018  View: PDF

Abstract: We demonstrate for the first time inscription and wet dissolution study of Bragg gratings in a bioresorbable calcium-phosphate glass optical fiber. Bragg gratings, with average refractive index changes of 5.8 x 10-⁴, were inscribed using 193 nm excimer laser radiation. Results on the dissolution of the irradiated fiber in simulated physiological conditions are presented after immersing a tilted Bragg grating in phosphate buffered saline solution for 4 days; selective chemical etching effects are also reported. The investigations performed pave the way towards the use of such phosphate glass fiber Bragg gratings for the development of soluble photonic sensing probes for the efficient in-vivo monitoring of vital mechanical or chemical parameters.

Terahertz Dyakonov-like surface waves in plasma metamaterials

Mostafa Moradi and Alireza Niknam

Doc ID: 315442 Received 12 Dec 2017; Accepted 27 Dec 2017; Posted 03 Jan 2018  View: PDF

Abstract: Metamaterials in which plasmas are included have significant properties that may not be found in ordinary metamaterials. The permittivity function of these engineered materials can be rapidly manipulated by applying external electric and magnetic field or changing the gas pressure, temperature and collisional frequency. We investigate the conditions necessary for the existence of Dyakonov-like surface waves (DLSWs) propagating along the interface of a plasma metamaterial (PMM) and an isotropic dielectric material in the terahertz region. We assume the PMM to be a multilayer structure which consists of plasma and background isotropic material alternately. The influence of considering the plasma collisional loss in the DLSW dispersion curve is studied. We demonstrate that the angular regions in which the DLSW propagation is allowed, can be tuned and significantly expanded. We also show that the large birefringence represented bythe PMM allows DLSWs, to exist within large angular existence domains and levels of localization similar to plasmons, thus making these surface waves available for practical applications.

Interplay of Kerr and Raman beam cleaning with a multimode microstructure fiber

Richard Dupiol, Katarzyna Krupa, Alessandro Tonello, Marc FABERT, Daniele Modotto, Stefan Wabnitz, Guy Millot, and Vincent COUDERC

Doc ID: 312489 Received 06 Nov 2017; Accepted 27 Dec 2017; Posted 03 Jan 2018  View: PDF

Abstract: We experimentally study the competition between Kerr beam self-cleaning and Raman beam cleanup in a multimode air-silica microstructure optical fiber. Kerr beam self-cleaning of the pump is observed for a certain range of input powers only. Raman Stokes beam generation and cleanup lead to both depletion and degradation of beam quality for the pump. The interplay of modal four-wave mixing and Raman scattering in the infrared domain lead to the generation of a multimode supercontinuum ranging from 500 nm up to 1800 nm.

Quantitative imaging of anisotropic material properties with vectorial ptychography

Patrick Ferrand, Arthur Baroni, Marc Allain, and Virginie Chamard

Doc ID: 314710 Received 30 Nov 2017; Accepted 26 Dec 2017; Posted 10 Jan 2018  View: PDF

Abstract: Following the recent establishment of the formalism of vectorial ptychography [Ferrand \emph{et al.}, Opt. Lett. 40, 5144 (2015)], first measurements are reported in the optical range, demonstrating the capability of the proposed method to map the four parameters of the Jone matrix of an anisotropic specimen, and therefore to quantify a wide range of optical material properties, including power transmittance, optical path difference, diattenuation, retardance, and fast-axis orientation.

Dual-wavelength digital holographic phase and fluorescence microscopy for optical thickness encoded suspension array

Zhiyuan Shen, Yonghong He, Gong Zhang, Qinghua He, Dongmei Li, and Yanhong Ji

Doc ID: 314733 Received 01 Dec 2017; Accepted 26 Dec 2017; Posted 08 Jan 2018  View: PDF

Abstract: A dual-wavelength digital holographic phase and fluorescence microscopy system is demonstrated as the decoding and detection platform of an optical thickness encoded suspension array. The phase imaging path is designed to decode optical thickness encoded microcarriers, and the fluorescence imaging path is used to detect the quantitative information of the bound target analytes. The encoding capacity could be more than 100. The decoding reliability of the phase imaging path is verified by a multiplexed immunoassay experiment. The ability for quantitative analysis of the fluorescence imaging path is confirmed by concentration gradient experiments. This method offers high decoding accuracy and high detection sensitivity of label signals.

Diameter Measurement of Optical Nanofiber Based on High-order Bragg Reflections Using a Ruled Grating

Ming Zhu, YAO-TING WANG, Yi-Zhi Sun, Lijian Zhang, and Wei Ding

Doc ID: 313666 Received 23 Nov 2017; Accepted 25 Dec 2017; Posted 03 Jan 2018  View: PDF

Abstract: A convenient method using commercially available ruled grating for precise and in-situ diameter measurement of optical nanofibers (ONFs) is presented. We form a composite Bragg reflector with a microscale period by dissolving aluminum coating, slicing the grating along ruling lines, and mounting it on an ONF. The resonant wavelengths of high-order Bragg reflections demonstrate fiber diameter dependence, enabling nondestructive measurement of ONF diameter profile. This method provides an easy and economic diagnostic tool for wide varieties of ONF-based applications.

Cloaking of metal grid electrodes on Lambertian emitters by free-form refractive surfaces

Martin Schumann, Benjamin Fritz, Ralph Eckstein, Uli Lemmer, Guillaume Gomard, and Martin Wegener

Doc ID: 312772 Received 06 Nov 2017; Accepted 24 Dec 2017; Posted 03 Jan 2018  View: PDF

Abstract: We discuss invisibility cloaking of metal grid electrodes on Lambertian light emitters by using dielectric free-form surfaces. We show that cloaking can be ideal in geometrical optics for all viewing directions if reflections at the dielectric-air interface are negligible. We also present corresponding white-light proof-of-principle experiments that demonstrate close-to-ideal cloaking for a wide range of viewing angles. Remaining imperfections are analyzed by ray-tracing calculations. The concept can potentially be used to enhance the luminance homogeneity of large-area organic light-emitting diodes.

High-performance on-chip autocorrelator using a rib waveguide loaded with two-photon absorption diodes

Keisuke Kondo and Toshihiko Baba

Doc ID: 313510 Received 14 Nov 2017; Accepted 24 Dec 2017; Posted 10 Jan 2018  View: PDF

Abstract: We report an on-chip autocorrelator comprising a Si rib waveguide and two-photon-absorption photodiodes in which two pulses simultaneously propagate in opposite directions, and their correlation is acquired. The rib waveguide’s broadband guiding mode and moderately low group index allow the device to operate over a wide wavelength range with high resolution. We confirm that the waveguide has a transmission band of at least 1300–1630 nm and observed correlation waveforms for pulses of the order of several hundred femtoseconds to several picoseconds, with a range of at least the entire C band region.

Measurement of the surface susceptibility and the surface conductivity of atomically thin MoS₂ by spectroscopic ellipsometry

Gaurav Jayaswal, Zhenyu Dai, Xixiang Zhang, Mirko Bagnarol, Alessandro Martucci, and Michele Merano

Doc ID: 307511 Received 25 Sep 2017; Accepted 23 Dec 2017; Posted 08 Jan 2018  View: PDF

Abstract: We show how to correctly extract from the ellipsometric data the surface susceptibility and the surface conductivity that describe the optical properties of monolayer MoS₂. Theoretically, these parameters stem from modelling a single-layer two-dimensional crystal as a surface current, a truly two-dimensional model. Currently experimental practice is to consider this model equivalent to a homogeneous slab with an effective thickness given by the inter-layer spacing of the exfoliating bulk material. We prove that the error in the evaluation of the surface susceptibility of monolayer MoS₂, owing to the use of the slab model, is at least 10% or greater, a significant discrepancy in the determination of the optical properties of this material.

Femtosecond laser tagging for velocimetry in argon and nitrogen gas mixtures

Yibin Zhang and Richard Miles

Doc ID: 309215 Received 18 Oct 2017; Accepted 23 Dec 2017; Posted 02 Jan 2018  View: PDF

Abstract: Tagging is demonstrated in argon and nitrogen gases using a femtosecond laser with pulse energies of approximately 70μJ through a nonresonant ionization process at 267nm. The signal fluorescence lifetime in pure argon and nitrogen-argon mixtures are measured and found to be long enough to make mean velocity and turbulence measurements in a subsonic flow. In pure argon, the dominating processes involve atomic transitions between 700 and 900nm. In argon-nitrogen mixtures, nitrogen quenches atomic argon species and the dominant radiating processes are transitions in the nitrogen second positive system. In pure nitrogen, emission on the microsecond timescale comes from the nitrogen first positive system. Lower energy density is needed for tagging and narrower tagged lines are produced using 267nm as compared to femtosecond laser tagging in argon and nitrogen using 400nm or 800nm. Velocimetry using the 267nm line is demonstrated in a turbulent argon pipe flow and the Taylor microscale of the flow is determined.

Asterisk-shaped Microstructured Fiber for an Octave Coherent Supercontinuum in a Sub-picosecond Region

Chunlei Huang, Meisong Liao, wanjun bi, Xia Li, Longfei Wang, Tianfeng Xue, Long Zhang, Danping Chen, Lili Hu, Yongzheng Fang, and Weiqing Gao

Doc ID: 317970 Received 18 Dec 2017; Accepted 22 Dec 2017; Posted 02 Jan 2018  View: PDF

Abstract: We selected two thermally matched silicate glasses with fair refractive index contrast and developed an asterisk-shaped all-solid microstructured optical fiber (MOF). The fiber presents a low, ultra-flat and all-normal dispersion in a wide wavelength range, allowing for the generation of an octave-spanning coherent supercontinuum (SC) in a 20 dB dynamic range with 0.5 ps pump pulses at 1.55 μm. This result improves the pump pulse duration that is only ~100 fs, related to the broadband and highly coherent SC generation in fibers with all-normal dispersion. This enables broadband SC sources with all-fiber, high-power, and highly coherent properties.

InP femtosecond mode-locked laser in compound feedback cavity with switchable repetition rate

Mu-Chieh Lo, Guillermo Carpintero, and Robinson Guzman

Doc ID: 313568 Received 15 Nov 2017; Accepted 22 Dec 2017; Posted 02 Jan 2018  View: PDF

Abstract: A monolithically integrated mode-locked semiconductor laser is proposed. The compound ring cavity is composed of a 1.6-mm colliding pulse mode locking subcavity and a 1.6-mm passive Fabry-Pérot feedback subcavity coupled at both ends, enabling hybrid mode locking. By changing DC-bias conditions, optical mode spacing from 50 up to 450 GHz are experimentally demonstrated. Ultrafast pulses shorter than 0.3 ps emitted from this laser diode are shown in autocorrelation traces.

High-power Yb-based all-fiber laser delivering 300-fs pulses for high-speed ablation-cooled material removal

Parviz Elahi, Hamit Kalaycioglu, Onder Akcaalan, Cansu Ertek, KORAY EKEN, and F Omer Ilday

Doc ID: 313894 Received 22 Nov 2017; Accepted 22 Dec 2017; Posted 02 Jan 2018  View: PDF

Abstract: We report on a 72-W Yb all-fiber ultrafast laser system with 1.6 GHz intra-burst and 200 kHz burst repetition rate developed to demonstrate ablation-cooled material removal at high speeds. Up to 24 W is applied on Cu and Si samples with compressed pulses of ∼300 fs. Record-high ablation efficiencies are obtained for Cu and Si, compared to published results to date, despite using only ∼100-nJ pulses. Ablation speeds approaching 1 mm³/s are reported with 24 W of average power, limited by available laser power and beam scanning speed. More significantly, these results experimentally confirm the theoretically expected linear scaling of the ablation-cooled regime to higher average powers without sacrificing efficiency, which implies that fur-ther scaling is possible with further increases in laser power and scanning speeds.

Performance enhancement of AlGaN-based 365-nm ultraviolet light-emitting diodes with band-engineering last quantum barrier

LongFei He, Wei Zhao, Kang Zhang, Chenguang He, Hualong Wu, Ningyang Liu, Weidong Song, Zhitao Chen, and Shuti Li

Doc ID: 314183 Received 29 Nov 2017; Accepted 22 Dec 2017; Posted 02 Jan 2018  View: PDF

Abstract: In this study, the characteristics of the AlGaN-based near-ultraviolet light-emitting diodes (NUV-LEDs) with band-engineering last quantum barrier (LQB) were analyzed experimentally and numerically. The experimental results show that the peak wavelengths of UV LEDs are around 368 nm with FWHM of 12-14 nm, and the optical and electrical properties are improved by using an AlxGa1-xN LQB with gradually decreasing Al content. The designed LQB can reduce the forward voltage from 4.35 to 4.29 V and markedly enhance light output power by 47.4% at an injection current of 200 mA, compared with the original structure. These improvements are mainly attributed to less electron leakage and higher hole injection efficiency, resulting from the weakened polarization field in the electron-blocking layer (EBL) and LQB as well as the alleviation of band bending at the EBL/LQB interface.

Reconfigurable photonic microwave convolver for pulse compression of phase-coded microwave waveform

Dexin Wu, Xiaoxiao Xue, Yirong Xu, Shangyuan Li, and Xiaoping Zheng

Doc ID: 314292 Received 27 Nov 2017; Accepted 22 Dec 2017; Posted 02 Jan 2018  View: PDF

Abstract: A reconfigurable photonic microwave convolver is proposed. The scheme is simply consisting of the evenly-spaced optical carriers (ESOCs), an optical dispersion module (ODM), a wavelength selector (WS), and a balanced photodetector (BPD). By adjusting the ESOCs, dispersion value of the ODM, and setup of the WS, the proposed convolver is reconfigurable. With the convolver, pulse compressions of the phase-coded microwave waveforms (PCMWs) are realized. Compressions of two PCMWs with respective coding rates of 1.8Gbit/s and 3.6Gbit/s are experimentally demonstrated. Full widths at half-maximum (FWHMs) of the main lobe are 0.56ns and 0.28ns, and the peak-to-side lobe ratios (PSRs) are 11.1dB and 11.3dB, respectively. Results are in agreement with the theoretical values. Besides, due to the flexible reconfigurability, it can adapt to various PCMWs by simple operation.

Broadband femtosecond nonlinear optical properties of CsPbBr3 perovskite nanocrystals

K N KRISHNAKANTH KATTURI, Sudipta Seth, Samanta Anunay, and Venugopal Rao Soma

Doc ID: 312923 Received 06 Nov 2017; Accepted 22 Dec 2017; Posted 05 Jan 2018  View: PDF

Abstract: We report the broadband nonlinear optical (NLO) properties of CsPbBr3 perovskite films achieved from colloidal nanocrystals prepared following room temperature and open atmosphere anti-solvent precipitation method. The NLO studies were performed on the films of nanocubes (NCs) and nanorods (NRs) using the Z-scan technique with 1 kHz repetition rate femtosecond pulses at 600, 700, and 800 nm. Large two-photon absorption cross-sections (~10^5 GM) were retrieved by fitting the open aperture Z-scan data. Strong third-order NLO susceptibility (~10-10 esu) was observed in these films. At higher peak intensities a switching of sign (both in NCs and NRs) in the real and imaginary parts of the NLO susceptibility was observed from the studies on these CsPbBr3 nanocrystals. Our results and the obtained NLO coefficients clearly suggest these materials as promising for ultrafast photonic applications.

Recovering a hidden polarization by ghost polarimetry

Wolfgang Elsaesser, Patrick Janassek, and Sébastien Hartmann

Doc ID: 313224 Received 13 Nov 2017; Accepted 22 Dec 2017; Posted 09 Jan 2018  View: PDF

Abstract: By exploiting polarization correlations of light from a broad-band fiber-based amplified spontaneous emission (ASE) source we succeed in reconstructing a hidden polarization in a ghost polarimetry experiment in close analogy to ghost imaging and ghost spectroscopy. Thereby, an original linear polarization state in the object arm of a Mach-Zehnder interferometer configuration which has been camouflaged by a subsequent depolarizer is recovered by correlating it with light from a reference beam. The variation of a linear polarizer placed inside the reference beam results in a Malus law type second order intensity correlation with high contrast, thus measuring a ghost polarigram.

Large brightness enhancement for continuous wave beams by diamond Raman laser conversion

Zhenxu Bai, Robert Williams, Hadiya Jasbeer, Soumya Sarang, Ondrej Kitzler, Aaron McKay, and Richard Mildren

Doc ID: 302313 Received 30 Aug 2017; Accepted 21 Dec 2017; Posted 04 Jan 2018  View: PDF

Abstract: High average power lasers with high beam quality are critical for emerging applications in industry and research for defence, materials processing and space applications. However, overcoming thermal effects in the gain medium remains the key challenge for increasing laser brightness at high powers. Here we report a new means for increasing beam brightness at high powers based on external cavity Raman lasers using diamond, a material with thermal properties far superior to any other laser material. With the pump beam quality in the range M2 = 2.3-7.3, up to 390 W pump-limited 1240 nm output is demonstrated with an M2 of 1.1 and increases in brightness from the pump by factors as high as 12.7. The influence of pump beam quality on laser threshold and slope efficiency is analyzed. This work foreshadows an alternative approach for scaling brightness of continuous-wave lasers using high-power, moderate beam quality pumps up to M2=20 or more, such as thin-disk and slab lasers and fiber lasers operating in the modal instability regime.

Ultraslow long-living plasmons withelectromagnetically induced transparency

Karolina Slowik, David Ziemkiewicz, and Sylwia Zielińska-Raczyńska

Doc ID: 314706 Received 30 Nov 2017; Accepted 21 Dec 2017; Posted 22 Dec 2017  View: PDF

Abstract: We analytically examine propagation of surface plasmon polaritons (SPPs) at a thin metallic film between glass substrate and electromagnetically-induced-transparency (EIT) medium. High-precision and high-resolution in frequency domain provided by EIT paves the way towards plasmonic group velocities reduction even by up to 4 orders of magnitude and correspondinglifetime enhancement of SPPs up to microseconds.

Bound states in the continuum in a two-dimensional PT-symmetric system

Yaroslav Kartashov, Carles Milian Enrique, Vladimir Konotop, and Lluis Torner

Doc ID: 314666 Received 30 Nov 2017; Accepted 20 Dec 2017; Posted 02 Jan 2018  View: PDF

Abstract: We address a two-dimensional parity-time-symmetric structure built as a chain of waveguides, where all waveguides except for the central one are conservative, while the central one is divided into two halves with gain and losses. We show that such a system admits bound states in the continuum (BICs) whose properties vary drastically with the orientation of the line separating amplifying and absorbing domains, which sets the direction of internal en-ergy flow. When the flow is perpendicular to the chain of the waveguides, narrow BICs emerge when the standard defect mode, which is initially located in the finite gap, collides with another mode in a standard symmetry breaking scenario and its propagation constant enters the continuous spectrum upon increase of the strength of gain/losses. In contrast, when the energy flow is parallel to the chain of the waveguides, the symmetry gets broken even for a small strength of the gain/losses. In that case, the most rapidly growing mode emerges inside the continuous spectrum and realizes a weakly localized BIC. All BICs found here are the most rapidly growing modes, therefore they can be excited from noisy inputs and, importantly, should dominate the beam dynamics in experiments.

30.5 μJ, 10 kHz, Picosecond Optical Parametric Oscillator with Intracavity Pumped Synchronously by a Regenerative Amplifier

Li He, Ke Liu, Bo Yong, Zhao Liu, Xiao-Jun Wang, Feng Yang, Lei Yuan, qinjun peng, Da Cui, and Xu Zuyan

Doc ID: 314002 Received 22 Nov 2017; Accepted 20 Dec 2017; Posted 03 Jan 2018  View: PDF

Abstract: We proposed a novel approach to realize high energy ultrafast optical parametric oscillator (OPO) by intracavity pumping in a regenerative amplifier. In this way, we experimentally demonstrated an unprecedented pulse energy of 30.5 μJ from a 1.5 μm singly resonant synchronously pumped OPO at the pulse repetition rate of 10 kHz with the pulse width of 7.0 ps. To the best of our knowledge, this is the highest pulse energy from an ultrafast laser OPO.

250W Clad pumped Raman fiber laser with brightness enhancement

Yariv Shamir, Yaakov Glick, Matitya Aviel, Shaul Pearl, and Avital Attias

Doc ID: 307663 Received 25 Sep 2017; Accepted 20 Dec 2017; Posted 08 Jan 2018  View: PDF

Abstract: We report a strictly all-fiber clad pumped Raman fiber laser with a CW power of 250 Watt. To the best of our knowledge this is the highest power Raman fiber laser demonstrated in any configuration allowing brightness enhancement. The brightness of the pump source was enhanced by a factor of ~3.8. This result was achieved by the design of a novel multi-clad fiber, with tight pump power inner confining clad that both maximized the Raman gain and inhibited the second Stokes radiation. We discuss power-increase effect on brightness enhancement, efficiency as well as beam quality variations.

In Vivo Broad-band Visible Light Optical Coherence Tomography Probe Enables Inverse Spectroscopic Analysis

James Winkelmann, Aya Eid, The-Quyen Nguyen, Thang Bui, Ji Yi, and Vadim Backman

Doc ID: 313344 Received 15 Nov 2017; Accepted 19 Dec 2017; Posted 05 Jan 2018  View: PDF

Abstract: We report the design and characterization of a 6 mm outer diameter pull-back circumferential scanning visible optical coherence tomography probe. The probe’s large visible bandwidth (500-695 nm) allowed for inverse spectroscopic analysis and an axial resolution of ~1.1 microns in tissue. We verify spectral imaging capabilities by measuring microsphere backscattering spectra and demonstrate in vivo spatial nanoscale characterization of tissue.

Multiple Scattering of Light in Discrete Random Media Using Incoherent Interactions

Karri Muinonen, Johannes Markkanen, Timo Väisänen, Jouni Peltoniemi, and Antti Penttilä

Doc ID: 315703 Received 14 Dec 2017; Accepted 17 Dec 2017; Posted 05 Jan 2018  View: PDF

Abstract: We consider scattering and absorption of light in discrete random media of densely packed spherical particles. In what we term radiative transfer with reciprocal transactions (R$^2$T$^2$), we introduce a volume element of the random medium, derive its scattering and absorption characteristics using the Superposition $T$-Matrix Method (STMM), and compute its frequency-domain incoherent volume-element scattering characteristics. Using an order-of-scattering approach, we then compute a numerical Monte Carlo solution for the scattering problem with an exact treatment of the interaction between two volume elements. We compute both the direct and reciprocal contributions along a sequence of volume elements, allowing us to evaluate the coherent-backscattering effects. We show that the R$^2$T$^2$ and exact STMM solutions are in mutual agreement for large finite systems of densely packed spherical particles. We conclude that the R$^2$T$^2$ method provides a viable numerical solution for scattering by asymptotically infinite systems of particles.

Suspended silicon waveguides for long-wave infrared wavelengths

J. Soler Penades, Alejandro Sánchez-Postigo, Milos Nedeljkovic, Alejandro Ortega-Moñux, J. Gonzalo Wangüemert-Pérez, Yolanda Xu Cheng, Robert Halir, Zhibo Qu, Ali Khokhar, Ahmed Osman, Wei Cao, Callum Littlejohns, Pavel Cheben, I. Molina-Fernández, and Goran Mashanovich

Doc ID: 312998 Received 08 Nov 2017; Accepted 14 Dec 2017; Posted 18 Dec 2017  View: PDF

Abstract: In this paper we report suspended silicon waveguidesoperating at a wavelength of 7.67 μm with a propagationloss of 3.1 ± 0.3 dB/cm. To our knowledge this isthe first demonstration of low loss silicon waveguidesat such a long wavelength, with loss comparable toother platforms that use more exotic materials. Thesuspended Si waveguide core is supported by a subwavelengthgrating that provides lateral optical confinement,while also allowing access to the buried oxidelayer so that it can be wet etched using hydrofluoricacid. We also demonstrate low loss waveguide bendsand s-bends.

Phosphor-in-glass with Nd-doped glass for a white LED with wide color gamut

Hansol Lee, Seonghyeon Kim, Jong Heo, and Woon Jin Chung

Doc ID: 310075 Received 03 Nov 2017; Accepted 09 Dec 2017; Posted 08 Jan 2018  View: PDF

Abstract: Phosphor in glass (PiG) with red and green phosphors using Nd-doped glass as a host matrix was fabricated to produce a white LED (wLED) with a wide color gamut. The Lu3Al5O12:Ce3+ and CaAlSiN3:Eu2+ content were adjusted to achieve white emission for liquid crystal display (LCD) applications. The silicate glass was doped with varying concentrations of Nd2O3 to modify the photoluminescence spectra of the wLED, by the hypersensitive absorption of the Nd3+:4I9/2→4G5/2,2G7/2 transition. Color coordination, color rendering index and color co-related temperature of the PiG mounted LEDs were modified by the introduction of Nd3+. The color gamut of the wLED was monitored and found to have effectively improved with theNd3+-doped silicate glass.

Evanescent field refractometry in planar optical fiber

Christopher Holmes, Alex Jantzen, Alan Gray, Paul Gow, Lewis Carpenter, Rex Bannerman, James Gates, and Peter Smith

Doc ID: 309889 Received 25 Oct 2017; Accepted 01 Dec 2017; Posted 06 Dec 2017  View: PDF

Abstract: This work demonstrates a refractometer in Integrated OpticalFiber (IOF), a new optical platform that planarizes fiber usingflame hydrolysis deposition (FHD). The unique advantage of thetechnology is its survivability in harsh environments. Theplatform is mechanically robust, can survive elevatedtemperatures approaching 1000oC and exposure to commonsolvents, including acetone, petrol and methanol. For thedemonstrated refractometer, fabrication was achieved throughwet etching an SMF-28 fiber to a diameter of 8 μm before FHDplanarization. External refractive index was monitored usingfiber Bragg gratings, written into the core of the planarizedfiber. A direct comparison to alternative fiber Bragg gratingrefractometers is made. The developed platform is shown tohave comparable sensitivities, with the added advantage ofsurvivability in harsh environments.

Homographically generated light-sheets for themicroscopy of large specimens

Craig Russell, Eric Rees, and Clemens Kaminski

Doc ID: 304060 Received 29 Sep 2017; Accepted 12 Nov 2017; Posted 21 Nov 2017  View: PDF

Abstract: We compare the performance of linear and nonlinear methods for aligning the excitation and detection planes throughout large specimen volumes in digitally scanned light sheet microscopy. An effective non-linear method involves registering four corner extrema of the imaging volume using a projective transform. We show this improves on the light collection efficiency of a 3-point affine registration by an average of 42% over a typical specimen volume, but increasingly higher-order corrections provide more modest returns. The accuracy of illumination/detection registration methods are now very pertinent to biological research in view of current trends towards imaging large or expanded samples, at depth, with diffraction limited resolution.

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