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Accepted papers to appear in an upcoming issue

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Dual fluorescence-absorption deconvolution applied to extended-depth-of-field microscopy

William Shain, Nicholas Vickers, awoke negash, Thomas Bifano, Anne Sentenac, and Jerome Mertz

Doc ID: 301292 Received 24 Aug 2017; Accepted 22 Sep 2017; Posted 22 Sep 2017  View: PDF

Abstract: Fast imaging over large volumes can be obtained in a simple manner with extended-depth-of-field (EDOF) microscopy. A standard technique of Wiener deconvolution can correct for the blurring inherent in EDOF images. We compare Wiener deconvolution with an alternative, parameter-free technique based on the dual reconstruction of fluorescence and absorption layers in a sample. This alternative technique provides significantly enhanced reconstruction contrast owing to a quadratic positivity constraint that intrinsically favors sparse solutions. We demonstrate the advantages of this technique with mouse neuronal images acquired in vivo.

Highly efficient, high peak-power, narrow linewidth fiber gas Raman amplifier operating at 1.9 μm

Zefeng Wang, Bo Gu, Yubin Chen, Xiaoming Xi, and zhixian li

Doc ID: 305571 Received 24 Aug 2017; Accepted 22 Sep 2017; Posted 22 Sep 2017  View: PDF

Abstract: We demonstrate here, to the best of our knowledge, the first 1.9 μm fiber gas Raman amplifier based on SRS in a H2-filled anti-resonance hollow-core fiber. A CW seed fiber laser near 1908 nm is amplified by the 1st vibrational Stokes wave of hydrogen molecules while pumping with a pulsed 1064 nm microchip laser. The seed significantly enhances the vibrational SRS and suppresses the rotational SRS, resulting in a record optical-to-optical conversion efficiency of ~41% and a corresponding quantum efficiency of ~73.5% for such H2 vibrational Raman experiments in hollow-core fibers, with 1.4 meter fiber and only 2 bar H2, which is more preferable in applications. The maximum average Stokes power of 74.2 mW with linewidth about 1 GHz (~12pm) is obtained, which also makes a record peak power of ~150 kW for sub-nanosecond 2μm- band fiber lasers of gigahertz-level linewidth. This paper provides a suitable laser source for the generation of supercontinuum and lasers at mid-infrared wavelength.

Overcoming the acoustic diffraction limit in photoacoustic imaging by localization of flowing absorbers

Sergey Vilov, Bastien Arnal, and Emmanuel Bossy

Doc ID: 303229 Received 26 Jul 2017; Accepted 21 Sep 2017; Posted 22 Sep 2017  View: PDF

Abstract: The resolution of photoacoustic imaging deep inside scattering media is limited by the acoustic diffraction limit. In this work, taking inspiration from super-resolution imaging techniques developed to beat the optical diffraction limit, we demonstrate that the localization of individual optical absorbers can provide super-resolution photoacoustic imaging well beyond the acoustic diffraction limit. As a proof-of-principle experiment, photoacoustic cross-sectional images of microfluidic channels were obtained with a 15 MHz linear CMUT array while absorbing beads were flown through the channels. The localization of individual absorbers allowed to obtain super-resolved cross-sectional image of the channels, by reconstructing both the channel width and position with an accuracy better than λ/10. Given the discrete nature of endogenous absorbers such as red blood cells, or that of exogenous particular contrast agents, localization is a promising approach to push the current resolution limits of photoacoustic imaging.

Subwavelength dielectric nanorod chains for energy transfer in the visible range

Li Dongdong, Jingjing Zhang, Chang-Chun Yan, Zhengji XU, and Dao Hua ZHANG

Doc ID: 304764 Received 16 Aug 2017; Accepted 21 Sep 2017; Posted 22 Sep 2017  View: PDF

Abstract: We report a new type of energy transfer device, formed by a dielectric nanorod array embedded in a silver slab. Such dielectric chain structures allow surface plasmon wave guiding with large propagation length and highly suppressed cross-talk between adjacent transmission channels. The simulation results show that our proposed design can be used to enhance the energy transfer along the waveguide-like dielectric nanorod chains via coupled plasmons, where the energy spreading is effectively suppressed, and superior imaging properties in terms of resolution and energy transfer distance can be achieved.

Wavelength Alteration Measurement Using Moire' Technique

Rahman Nouroozi, Amin Babazadeh, and Reza Eini Chenar

Doc ID: 305350 Received 23 Aug 2017; Accepted 21 Sep 2017; Posted 22 Sep 2017  View: PDF

Abstract: For convenient measurements in many applications, the wavelength alternations should be translated to the change in the intensity of the output light. In this letter, a novel method based on monitoring the Moire' pattern using a simple dispersive planoconvex lens (chromatic aberration) for wavelength alterations measurement is reported. Due to the chromatic aberration of the lens, different wavelengths have different magnifications. This causes rotation in Moire' pattern when the wavelength of the incident light is changed. It is shown that by measuring this rotation it is possible to measure the wavelength alterations. The experimental results obtained from four different laser sources with 450, 532, 630 and 632.8 nm wavelengths show total Moire' pattern rotation of about 31.5 degree which are in a good theory-experimental agreement. This method is simple and more reliable and might find wide applications in spectrometers, optical fiber sensors and dispersion measurements.

Are Hermite-Gaussian modes better than orbital angular momentum modes for free space optical communication?

Bienvenu Ndagano, nokwazi mphuthi, Giovanni Milione, and Andrew Forbes

Doc ID: 303548 Received 02 Aug 2017; Accepted 20 Sep 2017; Posted 22 Sep 2017  View: PDF

Abstract: There is interest in increasing the data speed of free-space optical communication by using spatial modes of light. In this particular application, intrinsic robustness to turbulence aberrations is key in choosing an ideal mode set to maximise transmission speed and efficiency. Here, we focus on the most significant turbulence aberration, namely, tip and tilt of the beam that results in misalignment, translating in lateral offsets of the beam at the receiver. We compared a subset of Hermite- and orbital angular momentum (OAM) carrying Laguerre-Gaussian modes, generated and measured with holographic filters, encoded on a spatial light modulator. The lateral offsets are realized by varying the central axis of symmetry of the measuring holograms, with respect to that of the transmitter which is kept fixed. We show that our subset of Hermite- Gaussian modes outperforms OAM modes, providing benefits for more robust communication across turbulent media.

Common-path spectral interferometry for single-shot terahertz electro-optics detection

Shuiqin Zheng, Xinjian Pan, Yi Cai, QINGGANG LIN, Ying Li, Shixiang Xu, Jingzhen Li, and Dianyuan Fan

Doc ID: 305122 Received 18 Aug 2017; Accepted 20 Sep 2017; Posted 22 Sep 2017  View: PDF

Abstract: We propose a common-path spectral interferometer for single-shot terahertz (THz) electro-optics (EO) detection, where a probe pulse pair with orthogonal polarizations and a relative time delay are generated by using simply a birefringent plate. One of them, as the object, transmits through THz EO crystal with THz phase modulation, while the other goes through the EO crystal without any phase imposed by target THz field as the reference. The co-axial propagation of the pulse pair can effectively reduce the noises due to mechanical vibrations, air turbulences, and temperature fluctuations in the traditional non-common-path spectral interferometers. Our experiments show, for a given target THz pulse field, the measured THz signals in single-shot mode have their signal-noise ratio (SNR) to be 41.2 with our THz common-path spectral interferometer but 7.91 with a THz Mach-Zehnder spectral interferometer, so our design improves the SNR of the THz signal by about 5.2 times.

Chip-scale nanophotonic switch based on waveguide-metamaterial coupling mechanism

Lei Chen, Han Ye, Yumin Liu, Zhongyuan Yu, dong wu, and Rui Ma

Doc ID: 305539 Received 25 Aug 2017; Accepted 20 Sep 2017; Posted 21 Sep 2017  View: PDF

Abstract: We demonstrate a simple and effective waveguide-metamaterial coupling mechanism to achieve switching control of the fundamental TE mode propagation in a silicon photonic stripe waveguide. The metamaterial is made of vertically stacked alternating ITO/Si layers, and can theoretically be switched between transparent and absorptive regimes via modifying the carrier concentration of the ITO layers. In addition to its small footprint and CMOS-compatible fabrication, simulation results indicate that the optical switch features a high modulation depth (MD) of 27.8dB, low insertion losses of 0.004dB, and a wide operating bandwidth of 300nm where the MD is >24.6dB. We expect this mechanism to be a good candidate for designing high-performance and ultra-compact photonic devices in densely-integrated nanophotonic circuits and computation systems.

Open-cavity fiber laser with distributed feedback based on externally or self- induced dynamic gratings

Ivan Lobach, Roman Drobyshev, Andrei Fotiadi, Evgeny Podivilov, Sergey Kablukov, and Sergey Babin

Doc ID: 302745 Received 18 Jul 2017; Accepted 20 Sep 2017; Posted 21 Sep 2017  View: PDF

Abstract: Dynamic population inversion gratings induced in an active medium by counter-propagating optical fields may have a reverse effect on the writing laser radiation via a feedback they provide. In this Letter, we report on the first demonstration of an open-cavity fiber laser in which the distributed feedback is provided by a dynamic grating “written” in an Yb-doped active fiber either by an external source or self-induced via a weak (~0.1%) reflection from an angle cleaved fiber end. It has been shown that rather a long (several meters) dynamic grating is formed with a narrow bandwidth (<50 MHz) and a relatively high reflection coefficient (>7%) securing single-frequency operation, but the subsequent hole-burning effects accompanied by new gratings formation lead to the switching from one longitudinal mode to another providing a regular pulse-mode dynamics. As a result, a periodically generated pulse trains cover a spectrum range of several THz delivering millions cavity modes in sequent pulses.

Flexible fs inscription of fiber Bragg gratings by an optimized deformable mirror

Thorsten A. Goebel, Christian Voigtländer, Ria Krämer, Daniel Richter, Maximilian Heck, Malte Siems, Christian Matzdorf, Claudia Reinlein, Michael Appelfelder, Thomas Schreiber, Jens Thomas, Andreas Tünnermann, and Stefan Nolte

Doc ID: 305110 Received 18 Aug 2017; Accepted 19 Sep 2017; Posted 20 Sep 2017  View: PDF

Abstract: The period of fiber Bragg gratings (FBG) is adapted by shaping the wavefront of ultrashort laser pulses applied in a phase mask inscription technique. A specially designed deformable mirror based on a dielectric substrate, to withstand high peak powers, is utilized to deform the wavefront. A shift of about 11 nm is demonstrated for a Bragg wavelength around 1550 nm.

LED-pumped Alexandrite laser oscillator and amplifier

Pierre Pichon, adrien barbet, Jean-Philippe Blanchot, Frederic Druon, Francois Balembois, and Patrick Georges

Doc ID: 302452 Received 13 Jul 2017; Accepted 19 Sep 2017; Posted 22 Sep 2017  View: PDF

Abstract: Taking advantage of LED performance breakthrough driven by the lighting market, we report the first LED-pumped chromium-doped crystal laser oscillator and amplifier based on alexandrite crystals (Cr3+:BeAl2O4). As pumped source, we developed a Ce:YAG concentrator illuminated by blue LEDs that can be easily power scaled. With 2200 LEDs (450 nm) the Ce:YAG concentrator can deliver to the gain medium up to 268 mJ at 10 Hz at 550 nm with a irradiance of 8.5 kW/cm2. We demonstrate, in oscillator configuration, a LED pumped alexandrite laser delivering an energy of 2.9 mJ at 748 nm in free running operation. In the cavity, we measured a double pass small signal gain of 1.28, in good agreement with numerical simulations. As amplifier, the system demonstrated to boost a CW Ti:sapphire laser by a factor of 4 at 750 nm in 8 passes with a large tuning range from 710 nm to 800 nm.

Narrow-Linewidth Microwave Generation by an Optoelectronic Oscillator with a Directly Modulated Microsquare Laser

Ming-Long Liao, Yong-Zhen Huang, Hai-Zhong Weng, Jun-Yuan Han, Zhi-Xiong Xiao, Jin-Long Xiao, and Yue-De Yang

Doc ID: 303714 Received 31 Jul 2017; Accepted 19 Sep 2017; Posted 22 Sep 2017  View: PDF

Abstract: A simple dual-loop optoelectronic oscillator using a 16-μm-side-length AlGaInAs/InP directly modulated microsquare laser is proposed and investigated without an external modulator. High-performance first harmonics are realized, with 3-dB linewidth less than 200 Hz and frequency tunable range from 2 to 8 GHz. Meanwhile, a side mode suppression ratio of 60 dB is obtained for the microwave by the dual-loop structure. Within the whole tuning range, the measured single sideband phase noises of the first harmonics are about -110 dBc/Hz at 10 kHz frequency offset. Furthermore, the second and third harmonics with frequency tunable range from 4 to 16 GHz and 6 to 24 GHz are achieved as well.

Point-by-Point Fabrication and Characterization of Sapphire Fiber Bragg Gratings

Shuo Yang, Di Hu, and Anbo Wang

Doc ID: 305378 Received 22 Aug 2017; Accepted 19 Sep 2017; Posted 22 Sep 2017  View: PDF

Abstract: The paper reports the inscription of fiber Bragg gratings (FBGs) in a single-crystal sapphire optical fiber via point-by-point method by 780 nm femtosecond (IR-fs) laser pulses. Compared to phase mask exposure, the use of the point-by-point method for the inscription provides a flexible way to fabricate sapphire FBGs and to make wavelength division multiplexing (WDM) in sapphire fiber more practicable. The multiplexing of three cascade gratings is demonstrated and their performance up to 1400℃ is tested. The permanent enhancement of reflectivity by a factor of about 5 after heat treatment and the nearly linear temperature response with slope of 25.8 pm/℃ are demonstrated.

Design of elliptical-core mode-selective photonic lanterns with six modes for MIMO-free mode division multiplexing systems

Xiaowei Sai, Yan Li, CHEN YANG, Wei Li, Jifang Qiu, Xiaobin Hong, Yong Zuo, Hongxiang Guo, Tong Weijun, and Jian Wu

Doc ID: 304886 Received 18 Aug 2017; Accepted 18 Sep 2017; Posted 22 Sep 2017  View: PDF

Abstract: Elliptical-core few mode fiber (EC-FMF) is used in mode division multiplexing (MDM) transmission system to release multiple-input-multiple-output (MIMO) digital-signal-processing (DSP), which reduces the cost and the complexity of the receiver. However, EC-FMF does not match with conventional multiplexers/de-multiplexers (MUXs/DeMUXs) such as photonic lantern (PL), leading to extra mode coupling loss and crosstalk. We design elliptical-core mode-selective photonic lanterns (EC-MSPLs) with six modes, which can match well with EC-FMF in MIMO-free MDM systems. Simulation of the EC-MSPL using beam propagation method was demonstrated employing a combination of either step-index or graded- index fibers with six different sizes of cores, and the taper transition length of 8 cm or 4 cm. Through numerical simulations and optimizations, both types of photonic lanterns can realize low loss transmission, and low crosstalk of below -20.0 dB for all modes.

Performance Optimization of PM-16QAM Transmission System Enabled by Real-time Self-adaptive Coding

Zhen Qu, Yao Li, Weiyang Mo, Mingwei Yang, shengxiang zhu, Daniel Kilper, and Ivan Djordjevic

Doc ID: 303968 Received 18 Aug 2017; Accepted 18 Sep 2017; Posted 20 Sep 2017  View: PDF

Abstract: We experimentally demonstrate self-adaptive coded 5×100Gb/s WDM polarization multiplexed 16 quadrature amplitude modulation (PM-16QAM) transmission over a 100-km fiber link, which is enabled by a real-time control plane. The real-time optical signal-to-noise ratio (OSNR) is measured using an optical performance monitoring (OPM) device. The OSNR measurement is processed and fed back using control plane logic and messaging to the transmitter side for code adaptation, where the binary data is adaptively encoded with three types of low-density parity-check (LDPC) codes with code rates of 0.8, 0.75, and 0.7 of large girth. The total code-adaptation latency is measured to be 2273 ms. Compared to transmission without adaptation, average net capacity improvements of 102%, 36%, and 7.5% are obtained respectively by adaptive LDPC coding.

On the manifestation of higher-order nonlinearities in a noble gas medium undergoing strong ionization

Miroslav Kolesik and Tyan-Lin Wang

Doc ID: 303384 Received 27 Jul 2017; Accepted 18 Sep 2017; Posted 21 Sep 2017  View: PDF

Abstract: While there is a consensus that higher-order effects beyond ${\chi}^{(3)}$ are present also in {\em high intensity} light-matter interactions,when and how they become apparent needs further study. The central question addressed in this work is if it is possible to design a situation inwhich they show up before being completely masked by the electrons freed by a high intensity field. The second question we attempt to answer is howmuch such observations, if and when feasible, can reveal about the nature ofthe nonlinear polarization. We answer the first question in affirmative, but ourcomparative simulations indicate that distinguishing the higher-ordernonlinearity from the third-order polarization can be extremely challenging.We also briefly discuss implications for the interpretation of the measured values of the nonlinear index.

Dipole force free optical control and cooling of nanofiber trapped atoms

Christoffer Østfeldt, Jean-Baptiste Béguin, Freja Pedersen, Eugene Polzik, Joerg Mueller, and Jurgen Appel

Doc ID: 304575 Received 11 Aug 2017; Accepted 18 Sep 2017; Posted 19 Sep 2017  View: PDF

Abstract: The evanescent field surrounding nano-scale optical waveguides offers an efficient interface between light and mesoscopic ensembles of neutral atoms. However, the thermal motion of trapped atoms, combined with the strong radial gradients of the guided light, leads to a time-modulated coupling between atoms and the light mode, thus giving rise to additional noise and motional dephasing of collective states. Here, we present a dipole force free scheme for coupling of the radial motional states, utilizing the strong intensity gradient of the guided mode and demonstrate all-optical coupling of the cesium hyperfine ground states and motional sideband transitions. We utilize this to prolong the trap lifetime of an atomic ensemble by Raman sideband cooling of the radial motion, which has not been demonstrated in nano-optical structures previously. Our work points towards full and independent control of internal and external atomic degrees of freedom using guided light modes only.

Hybrid optical pumping of K and Rb atoms in a paraffin coated vapor cell

Wenhao Li, Xiang Peng, Dmitry Budker, Arne Wickenbrock, Bo Pang, Rui Zhang, and Hong Guo

Doc ID: 305160 Received 18 Aug 2017; Accepted 18 Sep 2017; Posted 19 Sep 2017  View: PDF

Abstract: Dynamic hybrid optical pumping effects with a radio-frequency-field-driven nonlinear magneto-optical rotation (RF NMOR) scheme are studied in a dual-species paraffin coated vapor cell. By pumping K atoms and probing $^{87}$Rb atoms, we achieve an intrinsic magnetic resonance linewidth of 3 Hz and the observed resonance is immune to power broadening and light-shift effects. Such operation scheme shows favorable prospects for atomic magnetometry applications.

Flat top surface plasmon polariton beams

Lauren Zundel, Rosario Martinez-Herrero, and Alejandro Manjavacas

Doc ID: 305991 Received 31 Aug 2017; Accepted 18 Sep 2017; Posted 19 Sep 2017  View: PDF

Abstract: Surface plasmon polaritons (SPPs) have emerged as powerful tools for guiding and manipulating light below the diffraction limit. In this context, the availability of flat top SPP beams displaying a constant transversal profile can allow for uniform excitation and coupling scenarios, thus opening the door to developing novel applications that cannot be achieved using conventional Gaussian SPP beams. Here, we present a rigorous theoretical description of flat top SPP beams propagating along flat metal-dielectric interfaces. This is accomplished through the use of Hermite Gauss SPP modes that constitute a complete basis set for the solutions of Maxwell's equations for a metal-dielectric interface in the paraxial approximation. We provide a comprehensive analysis of the evolution of the transversal profiles of these beams as they propagate, which is complemented with the study of the width and kurtosis parameters. Our results serve to enlarge the capabilities of surface plasmon polaritons to control and manipulate light below the diffraction limit.

Precise identification of graphene layers at the air-prism interface via pseudo-Brewster angle

Chengquan Mi, Shizhen Chen, Weijie Wu, Wenshuai Zhang, Xinxing Zhou, Xiaohui Ling, Weixing Shu, Hailu Luo, and Shuangchun Wen

Doc ID: 305581 Received 25 Aug 2017; Accepted 18 Sep 2017; Posted 18 Sep 2017  View: PDF

Abstract: We propose a simple method for the precise identification of graphene layers at the air-prism interface via pseudo-Brewster angle where the horizontally polarized reflection is close to zero. We find that the pseudo-Brewster angle is sensitive to the variation of graphene layers where the pseudo-Brewster angle is approximately linearly increased about 0.5 degree as the layer numbers increased. Furthermore, the sensitivity of the pseudo-Brewster angle can be greatly enhanced and reaches 0.04 degree by eliminating the influence of cross-polarization effect. Our scheme can provide a simple and effective method to identify the layer numbers of graphene.

Experimental Realization of Quantum Random Number Generator with Independent Devices

Xue-bi An, Yun-Guang Han, Zhen-Qiang Yin, Wei Huang, Wei Chen, Shuang Wang, Guang-can Guo, and Zhengfu Han

Doc ID: 301041 Received 27 Jun 2017; Accepted 18 Sep 2017; Posted 18 Sep 2017  View: PDF

Abstract: The generation of genuine randomness is an important task in quantum information processing and it has attracted much more attention recently. How to estimate the genuine randomness of the data generated by a given device is a central problem. T. Lunghi et al. proposed a self-testing quantum random number generator [$Phys. Rev. Lett. 114, 150501(2015)$] from a prepare-and-measure scenario with independent devices. Based on this work, Y. G. Han et al. proposed a more efficient method [$Phys. Rev. A 93, 03 32(2016)$ ] (Han16 protocol for short) to estimate the genuine randomness. We here report a proof-of-principle realization of Han16 protocol with heralding single photon source. Because all observed probabilities are exploited to bound the minimum entropy of the output data, Han16 protocol is more efficient than T. Lunghi's protocol which only uses a dimension witness value. $H_{min}\sim0.307$ minimum entropy and $1.47kbits$ quantum random numbers per second are obtained in the experiment under fair-sampling assumption with Han16 protocol. The experimental results in different levels of noise and loss demonstrate that Han16 protocol almost doubles the generation rate of quantum random number with regard to the previous protocol. In addition, the performance of our experiment shows that Han16 protocol is practical and our experimental device can tolerate loss and noise.

Hybrid photonic-plasmonic near-field probe for efficient light conversion into the nanoscale hot spot

Alexander Koshelev, Keiko Munechika, and Stefano Cabrini

Doc ID: 301835 Received 01 Aug 2017; Accepted 17 Sep 2017; Posted 18 Sep 2017  View: PDF

Abstract: In this Letter, we present a design and simulations of the novel hybrid photonic-plasmonic near field probe. Near-field optics is a unique imaging tool that provides optical images with resolution down to tens of nanometers. One of the main limitations of this technology is its low light sensitivity. The presented hybrid probe solves this problem by combining a campanile plasmonic probe with a photonic layer, consisting of the diffractive optic element (DOE). The DOE is designed to match the plasmonic field at the base of the campanile probe with the fiber mode. This makes it possible to optimize the size of the campanile tip to convert light efficiently into the hot spot. The simulations show that the hybrid probe is on average ~540 times more efficient compared to the conventional campanile in the 600-900 nm spectral range.

Flat-top narrowband filters enabled by guided-mode resonance in two-level waveguides

Katsuaki Yamada, Kyu Lee, Yeong Ko, Junichi Inoue, Kenji Kintaka, Shogo Ura, and Robert Magnusson

Doc ID: 305182 Received 18 Aug 2017; Accepted 17 Sep 2017; Posted 18 Sep 2017  View: PDF

Abstract: Resonant nanogratings and periodic metasurfaces express diverse spectral and polarization properties on broadside illumination by incident light. Cooperative resonance interactions may yield shaped spectra for particular applications in contrast to multilayer dielectric mirror. Here, we provide guided-mode resonance filters with flat-top spectra suitable for wavelength division multiplexing systems. Applying a single one-dimensional grating layer sandwiched by two waveguides, we theoretically achieve high-efficiency flat-top spectra in the near-infrared region. This result is obtained by inducing simultaneous nearly-degenerate resonant modes. The resonance separation under this condition controls the width of the flat-top spectrum. This means we can implement spectral widths ranging from sub-nanometer to several nanometers applying fundamentally the same device architecture.

Enhanced Total Internal Reflection Using Low-Index Nanolattice Materials

Xu Zhang, Yi-An Chen, Abhijeet Bagal, and Chih-Hao Chang

Doc ID: 303972 Received 04 Aug 2017; Accepted 16 Sep 2017; Posted 19 Sep 2017  View: PDF

Abstract: Low-index materials are key components in integrated photonics and can enhance index contrast and improve performance. Such materials can be constructed from porous materials, which generally lack mechanical strength and are difficult to integrate. Here we demonstrate enhanced total internal reflection (TIR) induced by integrating robust nanolattice materials with periodic architecture between high-index media. The transmission measurement from the multilayer stack illustrates a cutoff at about 60º incidence angle, indicating enhanced light trapping effect through TIR. Light propagation in the nanolattice material is simulated using rigorous coupled-wave analysis (RCWA) and transfer matrix methods, which agrees well with experimental data. The demonstration of TIR effect in this work serves as a first step towards the realization of multilayer devices with nanolattice materials as robust low-index components. These nanolattice materials can find applications in integrated photonics, antireflection coatings, photonic crystals, and low-k dielectric.

Inversion of a two-level atom by quantum superoscillations

Ilya Doronin, A. Pukhov, E. Andrianov, Alexey Vinogradov, and Alexander Lisyansky

Doc ID: 298188 Received 16 Jun 2017; Accepted 15 Sep 2017; Posted 20 Sep 2017  View: PDF

Abstract: We show that a two-level atom with a high transition frequency ω_SO can be inverted via non-radiative interaction with a cluster of excited low-frequency two-level atoms or quantum oscillators whose transition frequencies are smaller than ω_SO. This phenomenon occurs due to the Förster resonant energy transfer arising during a train of quantum superoscillation of low-frequency two-level atoms. The suggested model could explain the mechanism of biophoton emission.

Nonlinear pulse compression stage delivering 43 W GW-class few-cycle pulses at 2 µm wavelength

Martin Gebhardt, Christian Gaida, Tobias Heuermann, Fabian Stutzki, Cesar Jauregui, Jose Antonio-Lopez, Axel Schulzgen, Rodrigo Amezcua Correa, Jens Limpert, and Andreas Tünnermann

Doc ID: 305502 Received 24 Aug 2017; Accepted 15 Sep 2017; Posted 15 Sep 2017  View: PDF

Abstract: High average power laser sources delivering intense few-cycle pulses in wavelength regions beyond the near-infrared are promising tools for driving the next generation of high-flux strong-field experiments. In this work, we report on nonlinear pulse compression to 34.4 µJ-, 2.1-cycle pulses with 1.4 GW peak power at a central wavelength of 1.82 µm and an average power of 43 W. This performance level was enabled by the combination of a high repetition rate ultrafast thulium-doped fiber laser system and a gas-filled antiresonant hollow-core fiber.

Hopping induced inversions and Pancharatnam excursions of C-points

Ruchi Rajput, B.S.Bhargava Ram, and Paramasivam Senthilkumaran

Doc ID: 305685 Received 25 Aug 2017; Accepted 14 Sep 2017; Posted 15 Sep 2017  View: PDF

Abstract: In this paper we show the acquisition of Pancharatnam phase by a C-point singularity when it is subjected to discrete cyclic polarization transformations. The SOP changes are mapped on to a Poincaré sphere as geodesical closed trajectories. Pancharatnam phase acquired by a C-point is equal to the solid angle subtended by the closed trajectories at the center of the Poincaré sphere. We show this by considering index hopping induced inversions of C-points. For example, a lemon from the North Pole of a Poincaré sphere is first converted into a star whose location can be traced to the South Pole of the Poincaré sphere and retrieved back as a lemon at theNorth Pole to complete a closed geodesical trajectory on the Poincaré sphere. Depending on the trajectory, it is shown that the lemons (stars) acquire different amount of Pancharatnam phase, which can be attributed to the amount of rotation in the SOP pattern of the lemons (stars).

Acceleratating two-dimensional infrared spectroscopywhile preserving lineshapes using GIRAF

Ipshita Bhattacharya, Jonathan Humston, Christopher Cheatum, and Mathews Jacob

Doc ID: 304846 Received 16 Aug 2017; Accepted 14 Sep 2017; Posted 15 Sep 2017  View: PDF

Abstract: We introduce a computationally efficient structuredlow rank algorithm for the reconstruction of twodimensionalinfrared (2D IR) spectroscopic data fromfew measurements. The signal is modeled as a combinationof exponential lineshapes, which are annihilatedby appropriately chosen filters. The annihilationrelations result in a low-rank constraint on a Toeplitzmatrix constructed from the signal samples, which is exploitedto recover the unknown signal samples. Quantitativeand qualitative studies on simulated and experimental2D IR data demonstrate that the algorithm outperformsdiscrete compressed sensing algorithm, bothin the uniform and non-uniform sampling settings.

Vertically-integrated spot-size converter in AlGaAs-GaAs

ZHONGFA LIAO, Sean Wagner, Muhammad Alam, Valery Tolstikhin, and J. Stewart Aitchison

Doc ID: 304327 Received 11 Aug 2017; Accepted 14 Sep 2017; Posted 18 Sep 2017  View: PDF

Abstract: We report on the demonstration of a spot size converter (SSC) for monolithic photonic integration at a wavelength of 850 nm on a GaAs substrate. We designed and fabricated a dual waveguide AlGaAs chip. The design consists of a lower waveguide layer for efficient end-fire coupling to a single mode fiber, and an upper waveguide layer for high refractive index contrast waveguides, and a vertical SSC to connect the two waveguide layers. We measured a SSC conversion efficiency of 91% (or −0.4 dB) between the upper and lower waveguide layers for the TE mode at a wavelength of 850 nm.

Soliton trapping and comb self-referencing in a single microresonator with χ(2) and χ(3) nonlinearities

Xiaoxiao Xue, Xiaoping Zheng, and Andrew Weiner

Doc ID: 303628 Received 01 Aug 2017; Accepted 14 Sep 2017; Posted 18 Sep 2017  View: PDF

Abstract: A shaped doublet pump pulse is proposed for simultaneous octave-spanning soliton Kerr frequency comb generation and second-harmonic conversion in a single microresonator. The temporal soliton in the cavity is trapped atop a doublet pulse pedestal, resulting in a greatly expanded soliton region compared to that with a general Gaussian pulse pump. The possibility of single-microresonator comb self-referencing in a single silicon nitride microring, which can facilitate compact on-chip optical clocks, is demonstrated via simulation.

Ex vivo validation of Photo-Magnetic Imaging

Alex Luk, Farouk Nouizi, Hakan Erkol, Mehmet Unlu, and Gultekin Gulsen

Doc ID: 304397 Received 08 Aug 2017; Accepted 14 Sep 2017; Posted 19 Sep 2017  View: PDF

Abstract: We recently introduced a new high resolution diffuse optical imaging technique termed Photo-Magnetic Imaging (PMI), which utilizes magnetic resonance thermometry (MRT) to monitor the 3D temperature distribution induced in a medium illuminated with a near-infrared light. The spatiotemporal temperature distribution due to light absorption can be accurately estimated using a combined photon propagation and heat diffusion model. High resolution optical absorption images are then obtained by iteratively minimizing the error between the measured and modeled temperature distributions. We have previously demonstrated the feasibility of PMI with experimental studies using tissue simulating agarose phantoms. In this Letter, we present the preliminary ex vivo PMI results obtained with a chicken breast sample. Similarly to the results obtained on phantoms, the reconstructed images reveal that PMI can quantitatively resolve an inclusion with a 3 mm diameter embedded deep in a biological tissue sample with only 10% error. These encouraging results demonstrate the performance of PMI in ex vivo biological tissue and its potential for in vivo imaging.

Fine-structure oscillations of noise-like pulses induced by amplitude modulation of saturable absorber

Xingliang Li, Shumin Zhang, Mengmeng Han, and Jingmin Liu

Doc ID: 305347 Received 23 Aug 2017; Accepted 14 Sep 2017; Posted 20 Sep 2017  View: PDF

Abstract: The generation and evolution process of noise-like pulses (NLPs) in an all-normal-dispersion nonlinear polarization rotation (NPR) mode-locked Yb-doped fiber laser are theoretically and experimentally investigated. We demonstrate that the amplitude modulation induced by reverse saturable absorption and the peak-power-limiting effect of the NPR plays a key role in the formation of fine-structure oscillations of NLPs. The average pulse width variation of the NLPs is also discussed in detail. We believe that our results can be used as a guide for the establishment of broadband NLP fiber laser sources.

Compact broadband spectrometer based on up- and down-conversion luminescence

Tao Yang, Jing-xiao Peng, Xing-ao Li, shen xiao, Xin-hui Zhou, Xiaoli Huang, Wei Huang, and Ho-Pui Ho

Doc ID: 306259 Received 01 Sep 2017; Accepted 13 Sep 2017; Posted 19 Sep 2017  View: PDF

Abstract: In this letter, a compact spectrometer based on up- and down-conversion luminescence for operation in the infrared, visible and ultraviolet bands is presented. The proposed spectrometer has three components that are used for dispersion, frequency conversion and detection. The conversion component converts the incident signal beam into a spectral window appropriate for the detection component. The detection component images the speckle pattern generated by scattering or diffraction in the random structure of the dispersion component. With the 2-dimensional intensity data captured from both the speckle pattern and a calibration measurement process, one can reconstruct the spectra of the signal beam by solving a matrix equation. A smoothing simulated annealing algorithm has been implemented to improve the accuracy of the spectral reconstruction. We have analyzed possible sources of error in the algorithm and the corresponding limits of operation. The reported broadband, compact, high-resolution luminescence-based spectrometer is well suited for portable spectroscopy applications.

Field extension inside guided-mode-resonance filters under a focused beam

Antoine Bierret, Grégory Vincent, Julien Jaeck, Jean-Luc Pelouard, Riad Haidar, and Fabrice Pardo

Doc ID: 306461 Received 06 Sep 2017; Accepted 13 Sep 2017; Posted 19 Sep 2017  View: PDF

Abstract: We present a theoretical study of mid-infrared guided mode resonance spectral filters made of two subwavelength metallic gratings and a dielectric waveguide, under a focused beam with a finite spot size. Study shows that, at the resonant wavelength, the lateral extension of the electromagnetic field in the waveguide is close to the width of the beam. We compare the performance of filters using gratings with a one-slit pattern and gratings with a two-slit pattern and we show that the latter gratings (biatom gratings) provide a higher transmission and a better limitation of field extension, due to an improved angular acceptance. These results open new perspectives for pixel-sized infrared filters.

Label-free brainwide visualization of senile plaque using cryo-micro-optical sectioning tomography

Yilin LUO, Anle Wang, Mengmeng Liu, Tian Lei, Xiaochuan Zhang, Zhaobing Gao, Hualiang Jiang, Hui Gong, and Jing Yuan

Doc ID: 303420 Received 01 Aug 2017; Accepted 13 Sep 2017; Posted 18 Sep 2017  View: PDF

Abstract: Optical visualization of pathological changes in Alzheimer’s disease (AD) can facilitate exploration of disease mechanism and treatment. However, existing optical imaging methods have limitations on mapping pathological evolution in the whole mouse brain. Previous research indicated endogenous fluorescence contrast of senile plaques. Therefore, we develop cryo-micro-optical sectioning tomography (cryo-MOST) to capture the intrinsic fluorescence distribution of senile plaque at a micron-level resolution in the whole brain. Validation using immunofluorescence demonstrates the capacity of cryo-MOST to visualize and distinguish senile plaques with competent sensitivity and spatial resolution. Compared with imaging in room temperature, cryo-MOST provides better signal intensity and signal-to-noise ratio. Using cryo-MOST, we obtained whole-brain coronal distribution of senile plaque in a transgenic mouse without exogenous dye. Capable of label-free brainwide visualization of Alzherimer’s pathology, cryo-MOST may be potentially useful for understanding neurodegenerative disease mechanism and evaluating drug efficacy.

Tunable spin Hall effect of light with graphene at telecommunication wavelength

Xiangxing Bai, Tang long, Wenqiang Lu, Xingzhan Wei, Shuang Liu, Xiudong Sun, Yang Liu, Haofei Shi, and Yueguang Lu

Doc ID: 302389 Received 11 Aug 2017; Accepted 13 Sep 2017; Posted 13 Sep 2017  View: PDF

Abstract: The Spin Hall effect of light (SHEL) has been widely studied of manipulating spin polarized photons. In the paper, we present a mechanism to electrically tune the spin shift of SHEL by means of introducing graphene layer at 1550 nm. The spin shift is quite sensitive to graphene layer near the Brewster angle for horizontal polarization incidence and can be dynamically tuned by varying the Fermi energy of graphene.We find that the position of the Brewster angle and the value of spin shift are decided by the real part and imaginary part of graphene conductivity respectively. In addition, two different tuned regions have been revealed, one is the “ step-like switch ” region where the spin shift switches between two values, and another is the “ negative modulation ” region where the spin shift declines gradually as Fermi energy increases. Those findings may provide a new paradigm for tunable spin photonic device.

Thulium-fiber-laser-pumped, high-peak-power, picosecond, mid-infrared orientation-patterned GaAs optical parametric generator and amplifier

Lin Xu, Qiang Fu, Sijing Liang, David Shepherd, David Richardson, and Shaif-Ul Alam

Doc ID: 303672 Received 31 Jul 2017; Accepted 12 Sep 2017; Posted 13 Sep 2017  View: PDF

Abstract: We report a high-peak-power, picosecond, mid-infrared optical parametric generator (OPG) and amplifier (OPA) based on orientation-patterned GaAs (OP:GaAs) pumped by a Tm:fiber master-oscillator-power-amplifier (MOPA) employing direct diode-seeded amplification. An OPG tuning range of 2550-2940 nm (signal) and 5800-8300 nm (idler) is demonstrated with peak powers as high as 3 kW (signal) and 2 kW (idler). When seeded with a 0.6 cm-1 linewidth tunable Cr:ZnSe laser, the OPA idler linewidth is narrowed to 1.4 cm-1 and a small-signal parametric gain of 60 dB is achieved. A maximum peak power of 13.3 kW (signal) and 3.2 kW (idler) is obtained at an overall conversion efficiency of 36%.

Arbitrary-shaped Brillouin microwave photonic filter by manipulating directly-modulated pump spectrum

Wei Wei, Lilin Yi, Yves Jaouen, and Weisheng Hu

Doc ID: 305090 Received 18 Aug 2017; Accepted 12 Sep 2017; Posted 13 Sep 2017  View: PDF

Abstract: We present a cost-effective GHz-wide arbitrary-shaped microwave photonic filter based on stimulated Brillouin scattering in fiber using directly-modulated laser (DML). After analyzing the relation between the spectral power density and the modulation current of the DML, we find the way to precisely adjust the optical spectrum of the DML thereby controlling the Brillouin gain filter spectrum arbitrarily for the first time. The manipulation of the pump spectrum consists of pre-designing the modulation current waveform and employing feedback control algorithm based on the targeted shape. The filter performance is evaluated by amplifying 500-Mbps non-return-to-zero on-off keying (NRZ-OOK) signal using a 1 GHz rectangular filter. The comparison between the proposed DML approach and the previous approach adopting complex IQ modulator (IQM) shows similar filter flexibility, shape fidelity and noise performance, proving that the DML-based Brillouin filter technique is a cost-effective and valid solution for microwave photonic applications.

Solitons in a $\PT$- symmetric $\chi^{(2)}$ coupler

Magnus Ogren, Fatkhulla Abdullaev, and Vladimir Konotop

Doc ID: 305223 Received 22 Aug 2017; Accepted 12 Sep 2017; Posted 13 Sep 2017  View: PDF

Abstract: We consider the existence and stability of solitons in a $\chitwo$ coupler. Both the fundamental and second harmonics undergo gain in one of the coupler cores and are absorbed in the other one. The gain and losses are balanced creating a parity-time ($\PT$) symmetric configuration. We present two types of families of $\PT$-symmetric solitons, having equal and different profiles of the fundamental and second harmonics. It is shown that gain and losses can stabilize solitons. Interaction of stable solitons is shown. In the cascading limit the model is reduced to the $\PT$-symmetric coupler with effective Kerr-type nonlinearity and balanced nonlinear gain and losses.

Characterization of depolarizing samples based on the indices of polarimetric purity

Albert Van Eeckhout, Angel Lizana, Enric Garcia-Caurel, Jose Gil, Razvigor Ossikovski, and Juan Campos

Doc ID: 301660 Received 05 Jul 2017; Accepted 12 Sep 2017; Posted 14 Sep 2017  View: PDF

Abstract: In this work we discuss the interest of using the Indices of Polarimetric Purity (IPPs) as a criterion for the characterization and classification of depolarizing samples. We proved how differences in the depolarizing capability of samples, not seen by the commonly used depolarization index PΔ, are identified by the IPPs. The above-stated result is analyzed from a theoretical point of view, and experimentally verified through a set of polarimetric measurements. We show how the approach here presented can be useful to easily synthetize depolarizing materials with controlled depolarizing features, just by properly combining low-cost fully polarizing materials (as linear retarders or polarizers).

Efficient wavelength conversion with low operation power in Ta₂O₅ based micro-ring resonator

Chung-Lun Wu, Jen-Yang Huang, Ding-Hsin Ou, Ting-Wei Liao, Yi-jen Chiu, Min-Hsiung Shih, YuanYao Lin, Ann-Kuo Chu, and Chao-Kuei Lee

Doc ID: 302655 Received 17 Jul 2017; Accepted 12 Sep 2017; Posted 14 Sep 2017  View: PDF

Abstract: The Ta₂O₅ based micro-ring resonator with unloaded quality factor of ~182000 has been demonstrated to realize efficient nonlinear wavelength generation. The propagation loss of Ta₂O₅ based micro-ring resonator is 0.5/cm, and the buildup factor of ring resonator is estimated to be ~50. With a high buildup factor of ring structure, the four-wave-mixing (FWM) conversion efficiency of -30dB is achieved in the Ta₂O₅ based micro-ring resonator with pump power of 6mW. Based on a power-dependent FWM results, the nonlinear refractive index of Ta₂O₅ is estimated to be 1.4E-14 cm²/W at wavelength of ~1550nm. The demonstration of enhanced FWM process in the Ta₂O₅ based micro-ring cavity implies the possibility of realizing FWM based optical parametric oscillation in Ta₂O₅ based micro-ring resonator.

Coherent Solid-State LIDAR with Silicon Photonic Optical Phased Arrays

Christopher Poulton, Ami Yaacobi, David Cole, Matthew Byrd, Manan Raval, Diedrik Vermeulen, and Michael Watts

Doc ID: 300540 Received 22 Jun 2017; Accepted 12 Sep 2017; Posted 12 Sep 2017  View: PDF

Abstract: We present the first demonstration of coherent solid-state LIDAR using optical phased arrays in a silicon photonics platform. An integrated transmitting and receiving frequency-modulated continuous-wave (FMCW) circuit was initially developed and tested to confirm on-chip ranging. Simultaneous distance and velocity measurements were performed using triangular frequency modulation. Transmitting and receiving optical phased arrays were added to the system for on-chip beam collimation and solid-state beam steering and ranging measurements using this system are shown. A cascaded optical phase shifter architecture with multiple groups was used to simplify system control and allow for a compact packaged device. This system was fabricated within a 300mm wafer CMOS-compatible platform and paves the way for disruptive low-cost and compact LIDAR on a chip technology.

Ultra-compact all-in-fiber-core Mach-Zehnder interferometer

Pengcheng Chen, Xuewen Shu, and Kate Sugden

Doc ID: 301535 Received 05 Jul 2017; Accepted 12 Sep 2017; Posted 12 Sep 2017  View: PDF

Abstract: Optical Mach-Zehnder interferometers (MZI) are useful components in a variety of optical applications including: optical modulation; signal processing; and physical, chemical, and biological sensing. We introduce here a novel, assembly-free all-in-fiber-core MZI, which is directly written with a femtosecond laser. By introducing a positive refractive index-modified zone (PRIMZ) in half of the fiber core, the original single-moded fiber section is converted into a few-moded fiber section, where a strong coupling between the two lowest-order guided modes is generated, resulting in a well-defined interference spectrum in transmission. This device promises many significant advantages over existing approaches such as: ease of fabrication; stability; small insertion loss; robustness; extremely broad operating bandwidth, and precise and controllable cavity lengths. These advantages make this device strikingly attractive with the potential for extensive adoption in fiber communications, signal processing, sensors and laser wavelength control.

Synthesis of circularly coherent sources

Massimo Santarsiero, Rosario Martinez-Herrero, David Maluenda Niubó, Juan Carlos de Sande, Gemma Piquero, and Franco Gori

Doc ID: 303522 Received 31 Jul 2017; Accepted 12 Sep 2017; Posted 18 Sep 2017  View: PDF

Abstract: An experiment is presented in which a partially coherent source endowed with circular coherence is generated. The source is synthesized through a time averaging procedure, so that the mutual intensity is used as the basic correlation function. The correlation between points at different radial distances from the source center is tested by means of a Young interferometer. To confirm the perfect coherence among points along a circle concentric with the source center, the Young mask is replaced by an array of equally spaced pinholes arranged along a circle. The observed pattern is identical to that produced by the same mask, illuminated by perfectly coherent light.

Phase-locked multi-terahertz electric fieldsexceeding 13 MV/cm at 190 kHz repetition rate

Matthias Knorr, Jürgen Raab, Maximilian Tauer, Philipp Merkl, Dominik Peller, Emanuel Wittmann, Eberhard Riedle, Christoph Lange, and Rupert Huber

Doc ID: 301260 Received 06 Jul 2017; Accepted 12 Sep 2017; Posted 18 Sep 2017  View: PDF

Abstract: We demonstrate a compact source of energetic and phase-locked multi-terahertz pulses at a repetition rate of 190 kHz. Difference frequency mixing of the fundamental output of an Yb:KGW amplifier with the idler of an optical parametric amplifier in GaSe and LiGaS2 crystals yields a passively phase-locked train of waveforms tunable between 12 and 42 THz. The shortest multi-terahertz pulses contain 1.8 oscillation cycles within the intensity FWHM. Pulse energies of up to 0.16 µJ and peak electric fields of 13 MV/cm are achieved. Electro-optic sampling reveals a phase stability better than 0.1 π over multiple hours combined with free CEP tunability. The scalable scheme opens the door to strong-field terahertz optics at unprecedented repetition rates.

A photoacoustic imaging methodology for the optical characterization of contact lenses

George Tserevelakis, Margarita Tsagkaraki, Miltiadis Tsilimbaris, Sotiris Plainis, and Giannis Zacharakis

Doc ID: 303700 Received 14 Aug 2017; Accepted 12 Sep 2017; Posted 18 Sep 2017  View: PDF

Abstract: We demonstrate photoacoustic microscopy as a metrology method for the optical characterization and quality control of Contact Lenses (CL). Dual wavelength excitation is applied to CLs tinted on either side with two thin ink layers, each of them possessing distinctly different optical absorption properties. The method is thus capable of measuring the elevation maps of both CL surfaces during two subsequent imaging sessions and extract the CL thickness, curvatures and dioptric power. We show that such an easily implementable technique provides robust, high precision, cost effective 3D imaging and characterization of both rigid and soft CLs, which render it highly favorable for a broad range of applications.

Fast and accurate modelling of nonlinear pulse propagation in graded-index multimode fibers

Matteo Conforti, Carlos Mas Arabi, Arnaud Mussot, and Alexandre Kudlinski

Doc ID: 304209 Received 04 Aug 2017; Accepted 12 Sep 2017; Posted 13 Sep 2017  View: PDF

Abstract: We develop a model for the description of nonlinear pulse propagation in multimode optical fibers with a parabolic refractive index profile. It consists in a 1+1D generalized nonlinear Schrodinger equation with a periodic nonlinear coefficient, which can be solved in an extremely fast and efficient way. The model is able to quantitatively reproduce recently observed phenomena like geometric parametric instability and broadband dispersive wave emission. We envisage that our equation will represent a valuable tool for the study of spatiotemporal nonlinear dynamics in the growing field of multimode fiber optics.

Intensity noise suppression in mode-locked fiber lasers by double optical bandpass filtering

Dohyun Kim, Shuangyou Zhang, Dohyeon Kwon, Ruoyu Liao, Yifan Cui, Zhigang Zhang, Youjian Song, and Jungwon Kim

Doc ID: 304758 Received 14 Aug 2017; Accepted 12 Sep 2017; Posted 14 Sep 2017  View: PDF

Abstract: We show that the relative intensity noise (RIN) of a mode-locked fiber laser can be suppressed below -140 dB/Hz level for the entire >20-Hz offset frequency range by a proper combination of intra-cavity and extra-cavity optical bandpass filters. When a 12-nm-bandwidth intra-cavity filter and a 16-nm-bandwidth extra-cavity filter are employed for a polarization-maintaining-nonlinear-amplifying-loop-mirror (PM-NALM)-based Er-fiber laser, the RIN spectrum level is suppressed by ~30 dB in the low offset frequency range. The resulting integrated rms RIN is only 0.0054% [1 Hz – 1 MHz], which is, to our knowledge, one of the lowest integrated RIN performances for any mode-locked lasers reported so far. Besides the simplicity, this double filtering approach has an additional advantage that, unlike active pump-laser feedback methods, it does not have any resonant peaks in the stabilized RIN spectrum. In addition to the RIN suppression, with intra-cavity bandpass filtering, the integrated rms timing jitter is also reduced from 7.29-fs (no-filter) to 2.95-fs (12-nm intra-cavity filter) [10 kHz – 1 MHz] in the soliton PM-NALM laser.

Multi-Channel Phase-Sensitive Amplification in a Low Loss CMOS-Compatible Spiral Waveguide

Young Zhang, Christian Reimer, JENNY WU, Piotr Roztocki, Benjamin Wetzel, Brent Little, Sai Tak Chu, David Moss, Benjamin Eggleton, Michael Kues, and Roberto Morandotti

Doc ID: 301503 Received 04 Jul 2017; Accepted 12 Sep 2017; Posted 20 Sep 2017  View: PDF

Abstract: Phase-sensitive amplification (PSA) has found broad use for optical regeneration, low-noise amplification, and the manipulation of non-classical light, among other applications. More recently, integrated PSA has been demonstrated in various Kerr platforms, allowing for simple, stable, and scalable implementations. However, the performance (e.g. extinction ratio or maximum gain) of PSA is limited by either high optical losses or material degradation. Here, we investigate PSA in a highly nonlinear, CMOS-compatible spiral waveguide with ultra-low linear and negligible nonlinear losses. In particular, we achieve a large net gain (>10 dB) and high extinction ratio (>24 dB) in single channel operation, as well as an extinction ratio of 15 dB spanning over a bandwidth of 24 nm for multiple channel operation. In addition, we derive an analytic solution that enables the calculation of the maximum phase-sensitive gain in any Kerr medium featured by linear and nonlinear losses. These results not only give a clear guideline for designing PSA-based amplifiers, but also show that it is possible to implement both optical regeneration and amplification in a single on-chip device, opening the route to investigations of more complex phenomena in integrated platforms, e.g. squeezed states of light.

Generation, amplification, frequency conversion and reversal of propagation of THz photons in nonlinear hyperbolic metamaterial

Alexander Popov and Sergey Myslivets

Doc ID: 301495 Received 04 Jul 2017; Accepted 11 Sep 2017; Posted 15 Sep 2017  View: PDF

Abstract: The metamaterial is proposed which supports a mixture of three or more normal and backward electromagnetic modes with equal co-directed phase velocities and mutually contra-directed energy fluxes. This enables extraordinary three-wave mixing, greatly enhanced optical parametric amplification and frequency-changing generation of entangled photons in the reflection direction. Proof-of-principle numerical simulation of such processes is presented based on the particular example of the wave-guided THz waves contra-propagating in the metamaterial made of carbon nanotubes.

Study of femtosecond laser induced circular optical properties in silica by Mueller matrix spectropolarimetry

Jing TIAN, Matthieu Lancry, SangHyuk YOO, Enric Garcia-Caurel, Razvigor Ossikovski, and Bertrand Poumellec

Doc ID: 305152 Received 18 Aug 2017; Accepted 11 Sep 2017; Posted 15 Sep 2017  View: PDF

Abstract: Transmission Mueller-matrix spectroscopic ellipsometry is applied to femtosecond laser induced modifications in silica glass in the spectral range 450–1000 nm. Within type II regime, the modifications exhibit not only circular dichroism but also circular birefringence. We suggest that the laser polarization orientation with respect to pulse front tilt determines the amplitude and the sign of the circular properties. By using differential decomposition of the Mueller matrix, optical rotation is revealed for the first time. A maximum value of the effective optical activity of 143°/mm at 550 nm is found.

Endoscopic optical coherence tomography with focus adjustable probe

Wenchao Liao, Tianyuan Chen, Chengming Wang, Wenxin Zhang, Zhangkai Peng, Xiao Zhang, Shengnan Ai, Deyong Fu, TieYing ZHOU, and Ping Xue

Doc ID: 303780 Received 01 Aug 2017; Accepted 11 Sep 2017; Posted 12 Sep 2017  View: PDF

Abstract: We present a focus adjustable endoscopic probe for optical coherence tomography (OCT), which is able to acquire images with different focal planes and overcome depth of focus limitations by image fusing. The use of two-way shape-memory-alloy spring enables the probe to adjust working distance over 1.5mm, providing large scanning range with high resolution and no sensitivity loss. Equipped with home-made hollow-core ultrasonic motor, the probe is capable of performing an unobstructed 360 degrees field-of-view distal scanning. The axial resolution and best lateral resolution are both ~4μm, with a sensitivity of 100.3dB. Spectral-domain OCT imaging of phantom and biological tissues with the probe is also demonstrated. © 2017 Optical Society of AmericaOCIS codes: (170.4500) Optical coherence tomography; (170.2150) Endoscopic imaging; (170.3880) Medical and biological imaging; (220.0220) Optical design and fabrication; (220.4000) Microstructure fabrication; ( 0.3990) Micro-optical devices.

A low cost 3D printed 1 nm resolution smartphone sensor based spectrometer: instrument design and application in ultraviolet spectroscopy

Thomas Wilkes, Andrew McGonigle, Jon Willmott, Tom Pering, and Joseph Cook

Doc ID: 304126 Received 04 Aug 2017; Accepted 11 Sep 2017; Posted 11 Sep 2017  View: PDF

Abstract: We report on the development of a low cost spectrometer, based on off-the-shelf optical components, a 3D printed housing and a modified Raspberry Pi camera module. With a bandwidth and spectral resolution of ≈ 60 nm and 1 nm, respectively, this device was designed with ultraviolet (UV) remote sensing of atmospheric sulphur dioxide (SO2), ≈ 310 nm, in mind. To the best of our knowledge, this is both the first report of a UV spectrometer, and of a nanometer resolution spectrometer, based on smartphone sensor technology. The spectrometer’s performance was assessed and validated by measuring the column amounts of SO2 within quartz cells, with a differential optical absorption spectroscopy processing routine. This system could easily be reconfigured to cover other spectral regions in the UV-visible-near-IR, as well as to provide alternate spectral ranges and/or linewidths. Hence, whilst a particular UV application area is documented here, our intention is also to highlight how this framework could be applied to build bespoke, low-cost, spectrometers for a range of other scientific applications.

Polarization-independent metalens constructed of antennas without rotational invariance

Hui Yang, Guanhai Li, Guangtao Cao, Zengyue Zhao, Feilong Yu, Xiaoshuang Chen, and Wei Lu

Doc ID: 305821 Received 28 Aug 2017; Accepted 11 Sep 2017; Posted 11 Sep 2017  View: PDF

Abstract: We proposed a novel approach to design an ultra-thin polarization-independent metalens (PIM) by utilizing antennas without rotational invariance. Two arrays of nanoblocks are elaborately designed to form the super cell of the PIM, which are capable of focusing right-handed circularly polarized (RCP) and left-handed circularly polarized (LCP) lights, respectively. With such a strategy, the PIM is able to achieve polarization-independent focusing since the light with any polarization can be treated as a combination of the two orthogonal ones. A theoretical analysis based on the Jones vector is proposed to detailedly explore the underlying physics. The polarization-independent characteristic of the designed PIM is also demonstrated by utilizing the finite difference time domain (FDTD) simulations. Moreover, polarization-independent focusing can be achieved within a wavelength range of 400nm. These results can deepen our understanding of polarization-independent focusing and provide a new method to design ultra-thin polarization-independent devices.

Generation of Two-Mode Frequency Degenerate Twin Beams in ⁸⁵Rb Vapor

jun jia, Wei Du, Jiefei Chen, Chunhua Yuan, Zhe-Yu Ou, and Weiping Zhang

Doc ID: 302872 Received 24 Jul 2017; Accepted 11 Sep 2017; Posted 11 Sep 2017  View: PDF

Abstract: We demonstrate a new phase-matching scheme for four-wave mixing processes in hot ⁸⁵Rb vapor, in which all four fields propagate in different directions but two of them are degenerate in frequency. When used as a parametric amplifier with an injected seed, two types of quantum mechanically correlated twin-beam states, either frequency degenerate or nondegenerate, can be generated. The quantum noise reduction in the intensity difference is almost 7 dB for the nondegenerate type and nearly 5 dB for the degenerate type over a wide frequency range. The spatial nondegeneracy of the four waves allows a variety of configurations of parametric processes, leading to flexible control for both phase insensitive and sensitive parametric amplification. The spatially nondegenerate but frequency degenerate four-wave mixing process will find wide applications in quantum metrology, quantum communication and quantum information of continuous variables.

Plasmonic Topological Insulators For Topological Nanophotonics

Weifeng Zhang, Xianfeng Chen, and Fangwei Ye

Doc ID: 301194 Received 28 Jun 2017; Accepted 10 Sep 2017; Posted 12 Sep 2017  View: PDF

Abstract: Photonic topological insulators are optical structures supporting robust propagation of light at their edges that are topologically protected from scattering. Here we propose the concept of plasmonic topological insulators that not only topologically protect light at the lattice edges but also enable their confinement and guidance at the deep-subwavelength scale. The suggested plasmonic topological insulators are composed of evanescently coupled array of metallic nanowires that are modulated periodically along the light propagation direction. The intrinsic loss associated with the plasmonic topological insulators is found not to deteriorate their topological protection on the edge modes. The marriage of topological photonics with nanophotonics opens up the possibility of topological nanophotonics.

Fabrication of disk droplets and evaluation of their lasing action

Mitsunori Saito, Takuya Hashimoto, and Jumpei Taniguchi

Doc ID: 302764 Received 18 Jul 2017; Accepted 09 Sep 2017; Posted 14 Sep 2017  View: PDF

Abstract: Disk resonators are difficult to create with droplets, since they self-form spheres due to the surface tension. In this study, disk (cylindrical) droplets were created by enclosing a dye (rhodamine 6G) solution in silicone rubber. Lasing actions of these droplets were examined by pulsed green laser excitation. In a large droplet (2 mm diameter), the whispering gallery mode emission was difficult to attain, since it competed with the radial or axial modes that made a round trip in the droplet. A disk droplet of 150 μm diameter exhibited a comb-like spectrum of the whispering gallery mode resonant emission.

Continuous tunable broadband emission of fluorphosphate glasses for single-component multi-chromatic phosphors

Ruilin Zheng, Qi Zhang, Ke-Han Yu, Chunxiao Liu, Jianyong Ding, Peng Lv, and Wei Wei

Doc ID: 304835 Received 18 Aug 2017; Accepted 09 Sep 2017; Posted 13 Sep 2017  View: PDF

Abstract: A kind of Sn2+/Mn2+ co-doped fluorphosphate (FP) glasses served as single-component continuous tunable broadband emitting multi-chromatic phosphors are developed for the first time. Importantly, these FP glasses have high thermal conductivity (3.25-3.70 W/m·K) and good chemical stability in water (80 oC). By combining with commercially available UV-LEDs directly, the emission colors can be tuned from blue/cold-white to warm-white/red through the energy transfer from Sn2+ to Mn2+, and the broadband spectra covering whole visible region from 380 nm to 760 nm. Notably, the FP glass can also service as a white light phosphor by controlling the content of SnO/MnO, which has excellent optical properties that, CIE chromaticity coordinate, CRI and QE are (0.33, 0.29), 84 and 0.952, respectively. These new phosphors, possessing of good optical and chemical properties, are promising for applications in solid-state lighting devices.

Enhanced photoluminescence from ring resonators in hydrogenated amorphous silicon thin films at telecommunications wavelengths

Ryan Patton, Michael Wood, and Ronald Reano

Doc ID: 303396 Received 01 Aug 2017; Accepted 09 Sep 2017; Posted 22 Sep 2017  View: PDF

Abstract: We report enhanced photoluminescence in the telecommunications wavelength range in ring resonators patterned in hydrogenated amorphous silicon thin films deposited via low temperature plasma enhanced chemical vapor deposition. The thin films exhibit broadband photoluminescence that is enhanced by up to 5 dB by the resonant modes of the ring resonators due to the Purcell effect. Ellipsometry measurements of the thin films show a refractive index comparable to crystalline silicon and an extinction coefficient on the order of 0.001 from 1300 nm to 1600 nm wavelength. The results are promising for chip-scale integrated optical light sources.

Adaptive Pre-Amplification Pulse Shaping in aHigh-Power, Coherently Combined Fiber Laser System

Nils Becker, Steffen Hadrich, Tino Eidam, Florian Just, Karoly Osvay, Zoltan Várallyay, Jens Limpert, Andreas Tünnermann, Thomas Pertsch, and Falk Eilenberger

Doc ID: 301803 Received 27 Jul 2017; Accepted 08 Sep 2017; Posted 08 Sep 2017  View: PDF

Abstract: We report on the successful implementation of a highly efficient adaptive pulse shaping technique in the ELI-HR high-power laser source. The pulse shaper is utilized to impose a gain flattening mask to increase the spectral width of the amplified pulse. Simultaneously, it pre-compensates for high order dispersion, acquired during stretching, multi-stage amplification and subsequent compression of the 8-channel, coherently combined main amplification stage. This result is expected to significantly enhance the performance of the fiber laser system and the subsequent nonlinear compression stages.

New classes of non-parity-time-symmetric optical potentials with all-real spectra and exceptional-point-free phase transition

Jianke Yang

Doc ID: 302381 Received 13 Jul 2017; Accepted 07 Sep 2017; Posted 08 Sep 2017  View: PDF

Abstract: Paraxial linear propagation of light in an optical waveguide with material gain and loss is governed by a Schr\"odinger equation with a complex potential. Properties of parity-time-symmetric complex potentials have been heavily studied before. In this article, new classes of non-parity-time-symmetric complex potentials featuring conjugate-pair eigenvalue symmetry in its spectrum are constructed by operator symmetry methods. Due to this eigenvalue symmetry, it is shown that the spectrum of these complex potentials is often all-real. Under parameter tuning in these potentials, phase transition can also occur, where pairs of complex eigenvalues appear in the spectrum. A peculiar feature of the phase transition here is that, the complex eigenvalues may bifurcate out from an interior continuous eigenvalue inside the continuous spectrum, in which case a phase transition takes place without going through an exceptional point. In one spatial dimension, this class of non-parity-time-symmetric complex potentials is of the form $V(x)=h'(x)-h^2(x)$, where $h(x)$ is an arbitrary parity-time-symmetric complex function. These potentials in two spatial dimensions are also derived. Diffraction patterns in these complex potentials are further examined, and unidirectional propagation behaviors are demonstrated.

Phase-measuring time-gated BOCDA

Alexia Lopez-Gil, Sonia Martin-Lopez, and Miguel Gonzalez Herraez

Doc ID: 301172 Received 30 Jun 2017; Accepted 07 Sep 2017; Posted 07 Sep 2017  View: PDF

Abstract: We demonstrate a simple scheme allowing to perform distributed Brillouin Phase Shift (BPS) measurements with very high spatial resolution (~ 7 cm) over long (~ 4.7 km) optical fibers. This is achieved by inserting a Sagnac interferometer (SI) in a Brillouin Optical Correlation Domain Analysis (BOCDA) configuration. Over its already-presented time-domain equivalent (SI-BOTDA), this approach reduces the main source of noise (coherent backscatter noise) thanks to the low-coherence nature of the used signals. On the other hand, over the most usual schemes used for distributed BPS measurements, this implementation presents the key advantage of not requiring high-bandwidth detection or complex modulation, while reaching unprecedented values of spatial resolution and number of resolved points for this type of measurements. Thanks to the linear dependence of the BPS feature around the Brillouin Frequency Shift (BFS), this scheme could also have the advantage of requiring shorter scanning ranges than amplitude-based configurations.

Mid-infrared 1 Watt hollow-core fiber gas laser source

Mengrong Xu, Fei Yu, and Jonathan Knight

Doc ID: 301281 Received 03 Jul 2017; Accepted 07 Sep 2017; Posted 13 Sep 2017  View: PDF

Abstract: We report the characteristics of a 1 Watt hollow-core fiber gas laser, emitting continuous-wave in the mid-infrared. Our system is based on an acetylene-filled hollow-core optical fiber, guiding with low losses at both the pump and laser wavelengths and operating in the single-pass ASE regime. By systematic characterization of the pump absorption and output power dependence on gas pressure, fiber length and pump intensity, we determine that the reduction of pump absorption at high pump flux and the degradation of gain performance at high gas pressure necessitate the use of increased gain fiber length for efficient lasing at higher powers. Low fiber attenuation is therefore key to efficient high-power laser operation. We demonstrate 1.1 Watt output power at 3.1 m wavelength from a single-pass configuration using a fiber length of 15 m at a pressure of 0.6 mbar, approximately 400 times higher CW output power than in the ring cavity previously reported.

Highly Sensitive Demodulation of Vibration-induced Phase Shift Based on a Low Noise OEO

Xiaofeng Jin, Zhu Yanhong, Jiaojiao Guo, Xiangdong Jin, Xianbin Yu, Shilie Zheng, Hao Chi, and Xianmin Zhang

Doc ID: 301341 Received 30 Jun 2017; Accepted 07 Sep 2017; Posted 12 Sep 2017  View: PDF

Abstract: A highly sensitive demodulation approach of vibration induced phase shift based on a low noise optoelectronic oscillator (OEO) is proposed and experimentally demonstrated. The vibration induced optical phase variation is directly converted to the electrical oscillating signal of OEO with carrier phase-shifted double sideband (CPS-DSB) modulation, which is realized by cascading a dual-output Mach-Zehnder modulator (DOMZM) and a fiber interferometer. Theoretically, within CPS-DSB modulated OEO, the minimum detectable optical phase shift is determined by the phase noise achievable and the sensitivity of optical phase shift demodulation no longer depends on its frequency. A proof-of-concept OEO oscillating at 100 MHz with ultralow phase noise is built up for demonstration. The achieved minimum detectable optical phase shift is 0.58 μrad at 1 kHz and 0.21 μrad at 10 kHz, which are the best results ever reported.

High-precision active synchronization control of high-power, tiled-aperture coherent beam combining

Peng Chun, Xiaoyan Liang, Ruxin Li, Li Wenqi, and Renqi Liu

Doc ID: 301799 Received 13 Jul 2017; Accepted 06 Sep 2017; Posted 11 Sep 2017  View: PDF

Abstract: We propose and demonstrate a high-precision active control technique for tiled-aperture coherent beam combining suitable for high-power laser pulses. The method is a hybrid structure based on the near-field interference fringe technique and single-crystal balanced optical cross-correlation, which enables the active loop to exhibit high accuracy, wide dynamic range, and good capacity for resisting energy disturbance. In the proof-of-principle experiment, we realized an adjustable beam combing bandwidth of approximately 100 Hz (limited by the speed of the piezo-electric transducer) and root-mean-square deviation of approximately λ/51 for two beam channels with a combining efficiency of 93%.

Modeling and calibrating nonlinearity and crosstalk in back focal plane interferometry for three-dimensional position detection

Peng Cheng, Sissy Jhiang, and Chia-Hsiang Menq

Doc ID: 303198 Received 27 Jul 2017; Accepted 06 Sep 2017; Posted 07 Sep 2017  View: PDF

Abstract: Back focal plane (BPF) interferometry is frequently used to detect the motion of a single laser trapped bead in photonic force microscope (PFM) system. Whereas this method enables high-speed and high-resolution position measurement, its measurement range is limited by nonlinearity coupled with crosstalk in three-dimensional (3-D) measurement and validation of its measurement accuracy is not trivial. This article presents an automated calibration system in conjunction with a 3-D quadratic measurement sensitivity model to render rapid and accurate calibration of the laser measurement system. An actively controlled 3-axis laser steering system and a high-speed vision-based 3-D particle tracking system are integrated to the PFM system to enable automatic and rapid calibration. The 3-D nonlinear model is utilized to correct for nonlinearity and crosstalk, and thus extend the 3-D position detection volume of back focal plane interferometry. We experimentally demonstrated a 12-fold increase in detection volume when applying the method to track the motion of a 2.0 µm laser trapped polystyrene bead.

Tunable Coffee-Ring Effect on a Superhydrophobic Surface

An He, Huan Yang, Wei Xue, Ke Sun, and Yu Cao

Doc ID: 303260 Received 28 Jul 2017; Accepted 06 Sep 2017; Posted 07 Sep 2017  View: PDF

Abstract: A tunable coffee-ring effect (CRE) that enables patterned deposition of nanoparticles (NPs) is obtained on the designed superhydrophilic and superhydrophobic composite surface of the titanium substrate. The low-adhesion superhydrophobic (LASH) surfaces with picosecond (ps) laser induced periodic surface structure (LIPSS) and micro-nano hierarchical structure (MNHS) are investigated. The NPs are not only deposited in a bitty area of 0.045mm² which is 265.56 times smaller than that of the original hydrophilic surface, but also in various patterns such as triangle, rectangle, eclipse besides the traditional circular shape. This controllable morphology of the CRE indicates a maneuvering capability of NPs in their common preservation form of suspension turbid liquid even when the solution concentration reaches 1 mg/mL, which is promising for the NPs printed circuit boards and the site-specific delivery drugs.

Wedge-shaped semiconductor nanowall arrays with excellent light management

Xinyu Chen, Jiang Wang, Shengchun Qin, Qiang Chen, Yali Li, Junshuai Li, and Deyan He

Doc ID: 304369 Received 09 Aug 2017; Accepted 06 Sep 2017; Posted 07 Sep 2017  View: PDF

Abstract: In this Letter, a light management structure composed of wedge-shaped semiconductor nanowall arrays is introduced. Theoretical investigation based on gallium arsenide (GaAs) indicates that a 1000 nm high array (wall base width/array periodicity: 500 nm) with an effective thickness of only 500 nm can deliver a maximum photocurrent density (Jph) of ~ 29.0 mA/cm2 at AM1.5G illumination (for an ideal absorber with the same bandgap, the corresponding value is ~ 32.0 mA/cm2.). However, Jph of a 1500 nm thick flat GaAs film is only ~ 19.2 mA/cm2 at the same illumination condition. The wedge-shaped nanowall arrays meanwhile exhibit good omnidirectional light confinement. At the incident angle of 60°, Jph of the aforementioned nanowall array is ~ 12.7 mA/cm2, and the corresponding value for an ideal absorber is ~ 16.0 mA/cm2. Considering the simple structure and excellent light confinement in a broad range of the system parameters including array periodicity, nanowall height and incident angle of light, the wedge-shaped semiconductor nanowall arrays provide a valuable platform for fabricating the related high performance-to-cost semiconductor optoelectronic devices.

Two-photon saturable absorption properties and laser Q-switch application of carbon quantum dots

shande Liu, Qiangguo Wang, Kai Wang, Yongping Yao, huiyun zhang, Tingqi Ren, Zhengmao Yin, Fanglin Du, Baitao Zhang, and Jingliang He

Doc ID: 304905 Received 21 Aug 2017; Accepted 06 Sep 2017; Posted 08 Sep 2017  View: PDF

Abstract: In this paper, high-quality carbon quantum dots (CQDs) with an average size of 15 nm are synthesized by using a solvothermal method. A CQDs saturable absorber mirror (SAM) was prepared, characterized and employed as an ultrafast optical switch successfully in a 1.0 μm solid-state laser. The saturable absorption effect (at 1 μm) far away from linear absorption band of the CQDs could be attributed to two-photon saturable absorption. The modulation depth (ΔT) and saturable energy intensity (Φs) of the CQDs-SA was measured about 4% and 15.34W/mm2, respectively. By using this SA, a Q-switched Nd:GdVO4 laser at 1 μm is firstly realized with the shortest pulse width of 66.8 ns and the maximum repetition rate of 1.13 MHz, respectively. The results indicate that CQDs may found to be another decent carbon SA materials for the applications in visible and infrared band.

A tunable kinoform X-ray beamsplitter

Maxime Lebugle, Gediminas Seniutinas, Felix Marschall, Vitaliy Guzenko, Daniel Grolimund, and Christian David

Doc ID: 301376 Received 09 Aug 2017; Accepted 06 Sep 2017; Posted 21 Sep 2017  View: PDF

Abstract: We demonstrate an X-ray beamsplitter with high performances for multi-keV photons. The device is based on diffraction on kinoform structures, which overcome the limitations of binary diffraction gratings. This beamsplitter achieves a dynamical splitting ratio in the range 0-99.1% by tilting the optics, and is tunable, here shown in a photon energy range of 7.2-19 keV. High diffraction efficiency of 62.6% together with an extinction ratio of 0.6% is demonstrated at 12.4 keV, with angular separation for the split beam of 0.5 mrad. This device can find applications in beam monitoring at synchrotrons, at X-ray free electron lasers for on-line diagnostics and beamline multiplexing, and possibly as key elements for delay lines or ultrashort X-ray pulses manipulation.

Capillary Red Blood Cell velocimetry by Phase-resolved Optical Coherence Tomography

Jianbo Tang, Sefik Evren Erdener, Buyin Fu, and David Boas

Doc ID: 305742 Received 28 Aug 2017; Accepted 05 Sep 2017; Posted 08 Sep 2017  View: PDF

Abstract: We present a phase-resolved Optical Coherence Tomography (OCT) method to extend Doppler OCT for accurate measurement of the red blood cell (RBC) velocity in cerebral capillaries. OCT data was acquired with an M-mode scanning strategy (repeated A-scans) to account for the single file passage of RBCs in a capillary, and then high pass filtered to remove the stationary component of the signal to ensure accurate measurement of phase shift of flowing RBCs. The angular frequency of the signal from flowing RBCs was then quantified from the dynamic component of the signal, and used to calculate the axial speed of flowing RBCs in capillaries. We validated our measurement by RBC passage velocimetry using the signal magnitude of the same OCT time series data.

Ramsey interferometry of a bosonic Josephson junction in an optical cavity

Sheng-Chang Li, Fu-Quan Dou, and Li-Bin Fu

Doc ID: 301357 Received 04 Jul 2017; Accepted 05 Sep 2017; Posted 07 Sep 2017  View: PDF

Abstract: We investigate the nonlinear Ramsey interferometry of a bosonic Josephson junction coupled to an optical cavity by applying two identical pumping field pulses separated by a holding field in the time domain. When theholding field is absent, we show that the atomic Ramsey fringes are sensitive to both the cavity-pump detuning and the initial state, and their periods can encode the information on both the atom-field coupling andthe atom-atom interaction. For a weak holding field, we find that the fringes characterized by the oscillation of the intra-cavity photon number can completely reflect the frequency information of the atomic interferencedue to the weak atom-cavity coupling. This finding allows a nondestructive observation of the atomic Ramsey fringes via the cavity transmission spectra.

Single camera shot interferenceless coded aperture correlation holography

Mani Rai, Vijayakumar Anand, and Joseph Rosen

Doc ID: 302253 Received 12 Jul 2017; Accepted 05 Sep 2017; Posted 07 Sep 2017  View: PDF

Abstract: We propose a new scheme for recording an incoherent digital hologram by a single camera shot. The method is based on a motionless, interferenceless, coded aperture correlation holography for 3D imaging. Two random-like coded phase masks (CPMs) are synthesized using Gerchberg-Saxton algorithm with two different initial random phase profiles. The two CPMs are displayed side by side and used as the system aperture. Light from a pinhole is introduced into the system and two impulse responses are recorded corresponding to the two CPMs. The two impulse responses are subtracted and the resulting intensity profile is used as a reconstructing hologram. A library of reconstructing holograms is created corresponding to all possible axial locations. Following the above training stage, an object is placed within the axial limits of the library and the intensity patterns of a single shot, corresponding to the same two CPMs, are recorded under identical conditions to generate the object hologram. The image of the object at any plane is reconstructed by a cross-correlation between the object hologram and the corresponding reconstructing hologram from the library.

Engineering steady-state entanglement via dissipation and quantum Zeno dynamics in an optical cavity

Dong Xiao Li, xq shao, Jin-Hui Wu, and x. x. yi

Doc ID: 302318 Received 14 Jul 2017; Accepted 05 Sep 2017; Posted 07 Sep 2017  View: PDF

Abstract: A new mechanism is proposed for dissipatively preparing maximal Bell entangled state of two atoms in an optical cavity. This scheme integrates the spontaneous emission, the light shift of atoms in the presence of dispersive microwave field, and the quantum Zeno dynamics induced by continuous coupling, to obtain a unique steady state irrespective of initial state. Even for a large cavity decay, a high-fidelity entangled state is achievable at a short convergence time, since the occupation of cavity mode is inhibited by the Zeno requirement. Therefore, a low single-atom cooperativity $C=g^2/(\kappa\gamma)$ is good enough for realizing a high fidelity of entanglement in a wide range of decoherence parameters. As astraightforward extension, the feasibility for preparation of two-atom Knill-Laflamme-Milburn state with the same mechanism is also discussed.

Measuring the electromagnetic chirality of 2D arrays under normal illumination

Xavier Garcia Santiago, Sven Burger, Carsten Rockstuhl, and Ivan Fernandez-Corbaton

Doc ID: 305177 Received 18 Aug 2017; Accepted 05 Sep 2017; Posted 12 Sep 2017  View: PDF

Abstract: We present an electromagnetic chirality measure for 2D arrays of subwavelength periodicities under normal illumination. The calculation of the measure uses only the complex reflection and transmission coefficients from the array. The measure allows the ordering of arrays according to their electromagnetic chirality, allowing a quantitative comparison of different design strategies. The measure is upper bounded, and the extreme properties of objects with high values of electromagnetic chirality make them useful in both near- and far-field applications. We analyze the consequences that different possible symmetries of the array have on its electromagnetic chirality. We use the measure to study four different arrays. The results indicate the suitability of helices for building arrays of high electromagnetic chirality, and the low effectiveness of a substrate for breaking the transverse mirror symmetry.

Radial-variant nonlinear ellipse rotation

Bo Wen, Yuxiong Xue, Gu Bing, Guanghao Rui, jun He, and Yiping Cui

Doc ID: 305261 Received 21 Aug 2017; Accepted 04 Sep 2017; Posted 08 Sep 2017  View: PDF

Abstract: The nonlinear ellipse rotation usually occurs when an elliptically polarized beam propagates through an isotropic nonlinear medium owing to the existence of χ₁₂₂₁ . Here we report the radial-variant nonlinear ellipse rotation of a vector beam with structured elliptical polarization through isotropic Kerr nonlinearities. Due to the interaction of elliptically polarized vector beams (EPVBs) with isotropic nonlinear media, the distributions of both the orientation angle and the ellipticity angle of beams at the far-field observational plane exhibit multiple concentric ring structures with the circularly symmetry. Numerical simulations show that the self-diffraction intensity pattern, the distribution of state of polarization, and the spin angular momentum (SAM) distribution of an EPVB could be manipulated by tuning both the isotropic optical nonlinearity and the chirality parameter of the vector beam, which may find direct applications in polarization-control optical switching, SAM manipulation, and optical polarization encoding or detection.

An extended polar decomposition method of Mueller matrices for birefringent turbid media

Ji Qi, Honghui He, Hui Ma, and Daniel Elson

Doc ID: 297981 Received 15 Jun 2017; Accepted 03 Sep 2017; Posted 11 Sep 2017  View: PDF

Abstract: The polar decomposition method for Mueller matrices proposed by Lu-Chipman has been demonstrated and validated for many applications. However, in some situations, the method may suffer from limitations due to the assumptions required by this method. Here we extended Lu-Chipman’s method and show that it can also be used to analyze turbid media where the scatterer sizes are comparable to or larger than the wavelength in reflection geometry. The method has been validated with experiments on turbid media. This work may thus prove useful in tissue polarimetry.

Broad bandwidth and large fabrication tolerance polarization beam splitter based on multimode anti-symmetric Bragg sidewall gratings

Huiye Qiu, Jiang jianfei, Ping Yu, Jianyi Yang, hui Yu, and Xiaoqing Jiang

Doc ID: 302524 Received 17 Jul 2017; Accepted 03 Sep 2017; Posted 07 Sep 2017  View: PDF

Abstract: A novel polarization beam splitter (PBS) based on an anti-symmetric sidewall Bragg grating in a multimode silicon-on-insulator strip waveguide is demonstrated. Anti-symmetric spatially periodic refractive-index perturbations are designed for strong coupling between the fundamental (TE0) and the first-order transverse electric modes (TE1), while not for TM modes. An adiabatic coupler is cascaded at the input-port so as to drop the TE1 reflection. The Bragg grating has a compact length of ~20 μm (55 periods). The polarization isolations of the through- and drop-ports at the wavelength of 1557 nm are 34 dB and 31 dB, respectively. A broad bandwidth of 64 nm and a large fabrication tolerance of 80 nm for polarization isolation over 20 dB are also achieved.

Mueller matrix polarimetry on a Young's double slit experiment analogue

Oriol Arteaga, Razvigor Ossikovski, Ertan Kuntman, mehmet kuntman, Adolfo Canillas, and Enric Garcia-Caurel

Doc ID: 297976 Received 12 Jun 2017; Accepted 03 Sep 2017; Posted 06 Sep 2017  View: PDF

Abstract: In this Letter we describe an experiment in which coherent light is sent through a calcite crystal that separates the photons by their polarization. The two beams are then let to superpose and this recombined beam is used to measure the Mueller matrix of the system. Results are interpreted according to our recent formalism of coherent superposition in material media. This is the first experimental implementation of a Young's experiment with complete polarimetry and it is demonstrated that our method can be used for the experimental synthesis of optical devices with on-demand optical properties.

Patterned multilayer metamaterial for fast and efficient photon collection from dipolar emitters

Oksana Makarova, Mikhail Shalaginov, Simeon Bogdanov, Alexander Kildishev, Alexandra Boltasseva, and Vladimir Shalaev

Doc ID: 303875 Received 08 Aug 2017; Accepted 02 Sep 2017; Posted 08 Sep 2017  View: PDF

Abstract: Solid state quantum emitters are prime candidates for the realization of fast on-demand single-photon sources. The improvement in photon emission rate and collection efficiency for point-like emitters can be achieved by using a near-field coupling to nanophotonic structures. Plasmonic metamaterials with hyperbolic dispersion have previously been demonstrated to significantly increase the fluorescence decay rates from dipolar emitters due to a large broadband density of plasmonic modes supported by such metamaterials. However, the emission coupled to the plasmonic modes must then be outcoupled into the far-field before it succumbs to ohmic losses. We propose a nano-grooved hyperbolic metamaterial that improves the collection efficiency by several times compared to a conventional planar lamellar hyperbolic metamaterial. Our approach can be utilized to achieve broadband enhancement of emission for diverse types of quantum emitters.

Frequency noise reduction performance of a feed-forward heterodyne technique: application to an actively mode-locked laser diode

Mohamed Omar Sahni, Stephane Trebaol, Laurent Bramerie, Michel Joindot, Sean O Duill, Stuart Murdoch, Liam Barry, and Pascal Besnard

Doc ID: 304128 Received 04 Aug 2017; Accepted 02 Sep 2017; Posted 11 Sep 2017  View: PDF

Abstract: We report on the frequency noise reduction performance of a feed-forward technique. The study is based on frequency noise measurements that allow the spectral response of the feed-forward phase noise correction to be determined. The main limitation to the noise compensation is attributed to the local oscillator flicker noise and the noise added by the optoelectronic loop elements. The technique is applied to an actively modelocked laser diode demonstrating, at the output of the system, an optical frequency comb source with 14 comb-lines reduced to sub-kHz intrinsic linewidth.

Resolution enhanced SOFI via structured illumination

Guangyuan Zhao, Cheng Zheng, Cuifang Kuang, and Xu Liu

Doc ID: 305287 Received 23 Aug 2017; Accepted 02 Sep 2017; Posted 11 Sep 2017  View: PDF

Abstract: By analyzing the statistics of the temporal fluctuations from the blinking emitters, statistics optical fluctuation imaging (SOFI) achieves super-resolution while imposing less constraints on the blinking behavior of the probes and are more suitable for low SNR acquisition than localization methods. However, determined by the square root of cumulation orders, the resolution improvement of SOFI highly restricts its promotion into high resolution observations. In this letter, abandoning the default flat illumination in stochastic imaging methods, we introduce structured illumination (e.g., Gaussian or sinusoidal pattern) into SOFI (SI-SOFI) to render greatly enhanced resolution. Through simulation with parameters of both real acquisition procedure and microscope properties, we examine the feasibility of SI-SOFI and obtain a resolution improvement of 4-6 folds at just 2nd order cumulation. Also, a practical pathway for the SI-SOFI reconstruction is offered.

OAM beam excitation using all-fiber weakly-fused mode selective coupler

Shankar Pidishety, Pachava Srinivas, Patrick Gregg, Siddharth Ramachandran, Gilberto Brambilla, and Balaji Srinivasan

Doc ID: 292548 Received 10 Apr 2017; Accepted 01 Sep 2017; Posted 12 Sep 2017  View: PDF

Abstract: OAM beam excitation through direct phase-matched coupling is experimentally demonstrated using an all-fiber weakly-fused mode selective coupler consisting of a single mode fiber and a ring-core vortex fiber. Experimental results showing the excited OAM mode purity of up to 75% measured through the standard ring technique not only demonstrates the proof of concept, but also provides a baseline for further improvement.

Type–II superlattice–based extended short–wavelength infrared focal plane array with an AlAsSb/GaSb superlattice etch–stop layer to allow near–visible light detection

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

Doc ID: 303880 Received 01 Aug 2017; Accepted 01 Sep 2017; Posted 13 Sep 2017  View: PDF

Abstract: A versatile infrared imager capable of imaging the near–visible to the extended short–wavelength infrared (e–SWIR) is demonstrated using e–SWIR InAs/GaSb/AlSb type–II superlattice–based photodiodes. A bi–layer etch–stop scheme consisting of bulk InAs0.91Sb0.09 and AlAs0.1Sb0.9/GaSb superlattice layers is introduced for substrate removal from the hybridized back–side illuminated photodetectors. The implementation of this new technique on an e–SWIR focal plane array results in a significant enhancement in the external quantum efficiency in the 1.8 to 0.8 μm spectral region while maintaining high quantum efficiency at the wavelengths longer than 1.8 μm. Test pixels exhibit 100% cut–off wavelengths of ~2.1 and ~2.25 μm at 150 and 300 K, respectively. They achieve saturated quantum efficiency values of 56% and 68% at 150 and 300 K, respectively, under back–side illumination and without any anti–reflection coating. At 150 K, the photodetectors (27×27 μm2 area) exhibit a dark current density of 4.7×10-7 A/cm2 under −50 mV applied bias providing a specific detectivity of 1.77×1012 cm•Hz1/2/W. At 300 K, the dark current density reaches 6.6×10-2 A/cm2 under -50 mV bias, providing a specific detectivity of 5.17×109 cm•Hz1/2/W.

Simplified Demultiplexing Scheme for Two PDM-IM/DD System Utilizing a Single Stokes Analyzer Over 25-km SMF

yan pan, Lianshan Yan, Anlin Yi, Lin Jiang, Wei Pan, Bing Luo, and Xihua Zou

Doc ID: 303732 Received 31 Jul 2017; Accepted 01 Sep 2017; Posted 11 Sep 2017  View: PDF

Abstract: We propose a four linear states of polarization (SOPs) multiplexed intensity modulation and direct detection (IM/DD) scheme based on two orthogonal polarization division multiplexing On-off keying (PDM-OOK) systems, and a simple demultiplexing algorithm for this scheme is experimentally demonstrated by utilizing only a single Stokes analyzer. At the rate of 4×10-Gbit/s, the experimental results show that the power penalty of proposed scheme is about 1.5-dB compared to the single PDM-IM/DD for back-to-back transmission. Compared to back-to-back, just about 1.7-dB power penalty is required after 25-km Corning® LEAF® optical fiber transmission. Meanwhile, the performance of the polarization tracking is evaluated, and the result show that the BER fluctuation is less than 0.5-dB with a polarization scrambling rate up to 708.75-deg/s.

High-order harmonic generations in intense mid IR fields by cascade 3-wave mixing in a fractal-poled LiNbO3 photonic crystal

Hyunwook Park, Antoine Camper, Kyle Kafka, Boqin ma, Yu Hang Lai, Cosmin Blaga, Pierre Agostini, Louis DiMauro, and Enam Chowdhury

Doc ID: 301219 Received 30 Jun 2017; Accepted 01 Sep 2017; Posted 06 Sep 2017  View: PDF

Abstract: We report on the generation of harmonic-like photon up-conversion in a LiNbO3-based nonlinear photonic crystal by mid-infrared femtosecond laser pulses. We study below bandgap harmonics of various driver wavelengths, reaching up to 11th order at 4 μm driver with 13% efficiency. We compare our results to numerical simulations based on two mechanisms: cascade 3-wave mixing and non-perturbative harmonic generation, both of which include quasi-phase matching. The cascade model reproduces well the general features of the observed spectrum including a plateau-like harmonic distribution and the observed efficiency. This has the potential for providing a source of tabletop few femtosecond UV pulses.

Generation of Broadband Terahertz Pulses via Optical Rectification in a Chalcopyrite CdSiP₂ Crystal

Brett Carnio, Peter Schunemann, Kevin Zawilski, and Abdulhakem Elezzabi

Doc ID: 305132 Received 18 Aug 2017; Accepted 31 Aug 2017; Posted 07 Sep 2017  View: PDF

Abstract: We report on the generation of broadband (0.07-6 THz) terahertz (THz) radiation via optical rectification in a <110> CdSiP2 (CSP) crystal pumped by a 50 fs, 780 nm central-wavelength optical pulse. By measuring the THz phase refractive index and the optical pump group refractive index, good phase matching can be achieved for a crystal thickness ≲200 µm. Due to this crystal’s high second order nonlinearity and low absorption losses, it is envisioned that THz generation from CSP could be further enhanced by confining the optical pump pulse to sub wavelength waveguides.

Self-interference digital holography with geometric-phase hologram lens

KiHong Choi, Junkyu Yim, Seunghwi Yoo, and Sung-Wook Min

Doc ID: 303057 Received 28 Jul 2017; Accepted 30 Aug 2017; Posted 07 Sep 2017  View: PDF

Abstract: Self-interference digital holography is actively studied because the hologram acquisition under the incoherent illumination condition is available. The key component in this system is a wavefront modulating optics, which modulates an incoming object wave into two different wavefront curvatures. In this letter, the geometric-phase hologram lens is introduced in the self-interference digital holography system, to perform as a polarization sensitive wavefront modulator, and a single-path beam splitter. This special optics has several features such as high transparency, up to 99% of modulation efficiency, thin as a few millimeters, and flat structure. The demonstration system is devised, and the numerical reconstruction results from an acquired complex hologram are presented.

Talbot Effect in Optical Lattices with Topological Charge

Jose Rodrigues, Caio Mendes, Eduardo Fonseca, and Alcenisio Silva

Doc ID: 303490 Received 27 Jul 2017; Accepted 30 Aug 2017; Posted 07 Sep 2017  View: PDF

Abstract: We studied the interference resulting of the superposition of the optical lattices, which are non-diffracting fields propagating in free space, and showed a Talbot self-imaging effect. These lattices are formed by spatially Fourier transforming a “quasi”-Orbital Angular Momentum (OAM) state. We experimentally observed that although the Talbot images change, the Talbot length is insensitive to the topological charge of the “quasi”-OAM state. Our findings can be useful for laser-written photonics lattices.

Kerr-lens mode-locked 2.3-µm Tm3+:YLF laser: a new source of femtosecond pulses in the mid infrared

Ferda Canbaz, Ismail Yorulmaz, and Alphan Sennaroglu

Doc ID: 303642 Received 31 Jul 2017; Accepted 30 Aug 2017; Posted 08 Sep 2017  View: PDF

Abstract: We report, what is to our knowledge, a new source of femtosecond pulses in the mid infrared, based on Kerr-lens mode-locked (KLM) Tm3+:YLF laser at 03 nm. An undoped ZnSe substrate was included in the resonator to provide enhanced nonlinear phase modulation during KLM operation. The Tm3+:YLF laser was end pumped with a continuous-wave Ti3+:sapphire laser at 780 nm. With 880 mW of pump power, we generated 514-fs pulses at a pulse repetition rate of 41.5 MHz with an average power of 14.4 mW. The spectral width (full width at half maximum) was measured as 15.4 nm, giving a time-bandwidth product of 0.44. We foresee that the wide availability of this gain medium as well as the straightforward pumping scheme near 800 nm will make 2.3-μm, mode-locked Tm3+:YLF lasers versatile sources of ultrashort pulses in the mid infrared.

Orthoscopic real-image display of digital holograms

Piotr Makowski, Tomasz Kozacki, and Weronika Zaperty

Doc ID: 300519 Received 21 Jun 2017; Accepted 30 Aug 2017; Posted 31 Aug 2017  View: PDF

Abstract: We present a practical solution for the long-standing problem of depth inversion in real-image holographic display of digital holograms. It relies on a field lens inserted in front of the spatial light modulator device addressed by a properly processed hologram. The processing algorithm accounts for pixel size and wavelength mismatch between capture and display devices in a way that prevents image deformation. Complete images of large dimensions are observable from one position with a naked eye. We demonstrate the method experimentally on a 10 cm long 3D object using a single HD spatial light modulator, but it can supplement most holographic displays designed to form a real image, including circular wide angle configurations.

Caustic beams from unusual powers of the spectral phase

Pablo Vaveliuk, Alberto Lencina, and Oscar Martinez Matos

Doc ID: 301905 Received 11 Jul 2017; Accepted 30 Aug 2017; Posted 06 Sep 2017  View: PDF

Abstract: Caustic optical beams arising from a spectral phase whose power lies in an unusual range of values less than two are presented. Unlike what happens for conventional phase powers greater than two, it is feasible to generate caustic structures having properties that do not follow the established sorting. For instance, an asymptotic cusp caustic beam having a cusp point at infinity is demonstrated. For the sake of completeness, the caustic beam properties are analyzed within the whole real range of the phase power. Accurate behavior rules between the symmetries of the beam spectral phase and its intensity distribution are founded. These findings strengthen the fundamentals and engineering on caustic beams in diverse optical and physical branches.

Polarization-independent broadband beam combining grating with measured over 98% diffraction efficiency from 10 nm to 1080nm

Junming Chen, YIBING ZHANG, Yonglu Wang, Fanyu Kong, Haopeng Huang, yanzhi wang, jin yunxia, Peng Chen, jiao xu, and jianda Shao

Doc ID: 303860 Received 01 Aug 2017; Accepted 29 Aug 2017; Posted 30 Aug 2017  View: PDF

Abstract: We report a grating solution for achieving broadband and polarization-independent properties to develop the laser combining system to much higher power levels. The grating with a high-refractive-index-contrast bilayer ridge was designed and successfully fabricated based on high power laser coatings, lithography and ion-beam etching technology. The measured −1st order non-polarized reflective diffraction efficiency of the grating exceeds 98% over the wavelength range of 1.0 -1.08μm and the highest value is 99.15%.

Dense Electro-optic Frequency Comb Generated by Two-stage Modulation for Dual-comb Spectroscopy

Wang Shuai, Xinyu Fan, Bingxin Xu, and Zuyuan He

Doc ID: 303999 Received 03 Aug 2017; Accepted 29 Aug 2017; Posted 30 Aug 2017  View: PDF

Abstract: Electro-optic frequency comb enables frequency-agile comb based spectroscopy without using sophisticated phase-locking electronics. Nevertheless, dense electro-optic frequency combs over broad spans have yet to be developed. In this work, we propose a straightforward and efficient method for electro-optic frequency comb generation with a small line spacing and a large span. This method is based on two-stage modulation: generating 18 GHz line-spacing comb at the first stage and 250 MHz line-spacing comb at the second stage. After generating an electro-optic frequency comb covering 1500 lines, we set up an easily established mutual-coherent hybrid dual-comb interferometer, which combines the generated electro-optic frequency comb and a free-running mode-locked laser. As a proof of concept, this hybrid dual-comb interferometer is used to measure the absorption and dispersion profiles of the molecular transition of H13CN with a spectral resolution of 250 MHz.

Controlled Modulation of Depolarization in Laser Speckle

Abhijit Roy, Rakesh Singh, and Maruthi Brundavanam

Doc ID: 303728 Received 01 Aug 2017; Accepted 29 Aug 2017; Posted 08 Sep 2017  View: PDF

Abstract: A new technique based on superposition of two speckle patterns is proposed and demonstrated for controlled modulation of the spatial polarization distribution of the resultant speckle. It is demonstrated both theoretically and experimentally that controlled modulation of the spatial polarization distribution of laser speckle can be achieved by proper choice of the polarization states as well as the average spatial intensity of the constituent speckles. It is shown that the proposed technique is useful to generate different speckle patterns with sinusoidal variation in their degree of polarization, which can be tuned from zero to unity. This technique can find application in sensing, biomedical studies, and in determining the rotation of an electric field vector after passing through a scattering medium.

Hybrid Non-linear Photoacoustic and Reflectance Confocal Microscopy for Label Free Subcellular Imaging with a Single Light Source

Scott Mattison, Eli Mondragon, Roland Kaunas, and Brian Applegate

Doc ID: 303191 Received 26 Jul 2017; Accepted 29 Aug 2017; Posted 08 Sep 2017  View: PDF

Abstract: Non-linear photoacoustic microscopy is capable of achieving subcellular optically resolved absorption contrast in 3-dimensions, but cannot provide structural context for the acquired images. We have developed a dual-modality imaging system which combines the optical absorption contrast of a non-linear photoacoustic microscope with the optical scattering contrast of a reflectance confocal microscope. By integrating the confocal detection optics into the optical setup of the non-linear photoacoustic microscope, the two systems were co-registered and may be acquired at the same time and with the same light source. Simultaneous images of fixed erythrocytes and fibroblasts were measured to demonstrate the complementary information that is provided by the two modalities.

Time-delay signature suppression in a chaotic semiconductor laser by fiber random grating induced random distributed feedback

Yanping Xu, Mingjiang Zhang, Liang Zhang, Ping Lu, Stephen Mihailov, and Xiaoyi Bao

Doc ID: 301557 Received 03 Jul 2017; Accepted 27 Aug 2017; Posted 06 Sep 2017  View: PDF

Abstract: We demonstrate that a semiconductor laser perturbed by distributed feedback with random time delays from a large number of scattering centers along a fiber random grating can emit light chaotically without the time-delay signature (TDS). A theoretical model is developed based on the modified Lang-Kobayashi model to numerically explore the chaotic dynamics of the laser diode subjected to random feedback. It is predicted that the random distributed feedback destroys the phase-correlated mode condition and hence suppresses the TDS. The fiber random grating is fabricated with random index modulation periods through point-by-point inscription, which introduces large numbers of phase-uncorrelated cavity modes into the semiconductor laser, leading to high dimensional chaotic dynamics and thus the concealment of the TDS. The experimentally obtained TDS value is negligible with a minimum of 0.0088, which is the smallest to date.

Closed-form expression for mutual intensity evolutionof Hermite-Laguerre-Gaussian Schell-model beams

Tatiana Alieva and Eugeny Abramochkin

Doc ID: 303385 Received 27 Jul 2017; Accepted 27 Aug 2017; Posted 07 Sep 2017  View: PDF

Abstract: We derive a comprehensive closed-form expression forthe evolution of the mutual intensity (MI) of Hermite-Laguerre-Gaussian Schell-model beams (HLG-SMBs)during propagation through rotationally symmetric op-tical systems. We demonstrate that the MI of the beamassociated with a given HLG mode at any transverseplane can be presented as a linear superposition of theMIs of the SMBs associated with the equal and lowerindex modes of the same type but of complex argu-ment. The obtained expression allows easily analyzingthe evolution of the intensity distribution and the cross-correlation function of such beams and, in particular,understanding the coherence singularity formation andmodification during the beam propagation.

Mode selecting switch using multimode interference for on-chip optical interconnects

Rubana Priti, Hamed Pishvai Bazargani, Yule Xiong, and Odile Liboiron-Ladouceur

Doc ID: 300832 Received 20 Jul 2017; Accepted 25 Aug 2017; Posted 25 Aug 2017  View: PDF

Abstract: A novel mode selecting switch (MSS) is experimentally demonstrated for on-chip mode-division multiplexed (MDM) optical interconnects. The MSS consists of a Mach-Zehnder interferometer (MZI) with tapered multi-mode interference (MMI) couplers and TiN thermo-optic phase-shifters for conversion and switching between the optical data encoded on the fundamental and first order quasi-transverse electric (TE) modes. The C-band MSS exhibits >25 dB switching extinction ratio (ER) and <-12 dB crosstalk. We validate the dynamic switching with a 25.8 kHz gating signal measuring switching times for both TE0 and TE1 modes of <10.9 μs. All channels exhibit less than 1.7 dB power penalty at 10¬¹² BER while switching the NRZPRBS-31 data signals at 10 Gb/s.

Efficient Mid-infrared Laser under Different Excitation Pump Wavelengths

Jing Liu, Jie Liu, Jimin Yang, Weiwei Ma, Qinghui Wu, and Liangbi Su

Doc ID: 304912 Received 16 Aug 2017; Accepted 25 Aug 2017; Posted 07 Sep 2017  View: PDF

Abstract: A laser operating at 2.8 μm in a lightly doped Er3+:SrF2 crystal is analyzed firstly for different excitation pump wavelengths: 972 nm and 1532 nm. A maximum output power of 814 mW was obtained by a 972-nm commercial laser diode (LD) and the corresponding slope efficiency was 30.4%. Laser emission under 1532 nm excitation was also achieved by efficient upconversion energy transfers. This could be an effective technique for realizing a compact and efficient upconversion laser capable of emitting in the mid-infrared regime.

Design of Structured YAG:Ce Scintillators with Enhanced Outcoupling for Image Detection in the Extreme Ultraviolet

Lukas Bahrenberg, Stefan Herbert, Tobias Mathmann, Serhiy Danylyuk, Jochen Stollenwerk, and Peter Loosen

Doc ID: 302710 Received 24 Jul 2017; Accepted 23 Aug 2017; Posted 06 Sep 2017  View: PDF

Abstract: In this Letter, the authors present a design study on YAG:Ce scintillator plates with a microstructured and coated surface. The goal of the study is to improve the outcoupling efficiency and to optimize the directionality of the scintillation light with respect to indirect image detection in the extreme ultraviolet spectral range (5 - 50 nm wavelength). In a geometric optical simulation, a gain in outcoupling efficiency by over a factor of four is shown while the directionality of the scintillation light is improved with respect to state-of-the-art plane scintillator plates.

Babinet’s principle for mutual intensity

Sergey Sukhov, Mahed Batarseh, Roxana Rezvani Naraghi, Heath Gemar, alexandru tamasan, and Aristide Dogariu

Doc ID: 300929 Received 26 Jun 2017; Accepted 18 Aug 2017; Posted 25 Aug 2017  View: PDF

Abstract: In classical diffraction theory, the Babinet’s principle relates the electromagnetic fields produced by complementary sources. This theorem was always formulated for single-point quantities, both intensities or field amplitudes, in conditions where the full spatial coherence is implicitly assumed. However, electromagnetic fields are, in general, partially coherent and their spatial properties are described in terms of two-point field-field correlation functions. In this case, a generalized Babinet’s principle can be derived that applies to the spatial coherence functions. We present both the derivation and the experimental demonstration of this generalized Babinet theorem.

Single Silicon CMOS platform for multi-spectral detection from THz to X-rays

Mostafa Shalaby, Carlo Vicario, and Christoph Hauri

Doc ID: 295247 Received 12 May 2017; Accepted 11 Aug 2017; Posted 24 Aug 2017  View: PDF

Abstract: Charge coupled devices (CCDs) is a well-established imaging concept in the visible and x-ray frequency ranges. However, the small quantum photon energies of terahertz (THz) radiation have hindered the use of this mature semiconductor technological platform in this frequency range, leaving THz imaging totally dependent on low-resolution bolometer technologies. Recently, it was shown that silicon CCDs can detect THz photons under special conditions but the detection sensitivity was limited. Here we show that silicon CMOS technology offers enhanced detection sensitivity of almost two orders of magnitude compared to CCDs. Our findings allow us to extend the low frequency THz cut off to less than 2 THz nearly closing the technological gap with electronic imagers operating up to 1 THz. Furthermore, with the CMOS technology being sensitive to mid infrared (midIR) and the x-ray ranges, we demonstrate multispectral detection with a single detector from 1 Exahertz to 2 THz. This overcomes the present challenge in spatially overlapping THz/midIR pump and x-ray probe radiation at facilities like free electron lasers, synchrotron and laser-based x-ray sources.

Atmospheric Boundary layer CO2 remote sensing with a direct detection LIDAR instrument based on a widely tunable optical parametric source

Erwan Cadiou, Dominique Mammez, Jean-Baptiste Dherbecourt, Guillaume Gorju, Jacques Pelon, Jean-Michel Melkonian, Antoine Godard, and Myriam Raybaut

Doc ID: 302785 Received 18 Jul 2017; Accepted 07 Aug 2017; Posted 07 Sep 2017  View: PDF

Abstract: We report on the capability of a direct detection differential absorption lidar (DIAL) for range resolved and integrated path (IPDIAL) remote sensing of CO2 in the atmospheric boundary layer (ABL). The laser source is an amplified nested cavity Optical Parametric Oscillator (NesCOPO) emitting about 8 mJ at the two measurement wavelengths selected near 2050 nm. Direct detection atmospheric measurements are taken from the ground using a 30 Hz frequency switching between emitted wavelengths. Results show that comparable precision measurements are achieved in DIAL and IPDIAL modes (not better than a few ppm) on high SNR targets such as near range ABL aerosol and clouds, respectively. Instrumental limitations are analysed and degradation due to cloud scattering variability is discussed to explain observed DIAL and IPDIAL limitations.

Study on focusing of subwavelength imaging of point source based on two-dimensional photonic crystals

liang ming, Ma Liang, Songlin Zhuang, Jinke Niu, and Jiabi Chen

Doc ID: 298223 Received 20 Jun 2017; Accepted 25 Jul 2017; Posted 07 Sep 2017  View: PDF

Abstract: A new focusing structure based on two-dimensional (2D) photonic crystal (PC) with the negative refraction and subwavelength imaging characteristics is proposed, consisting of periodic array air holes in silicon. The light radiated from a point source can form a subwavelength imaging of which half-width reaches 0.47λ through a wedge PC. Due to the influence of the phase difference and evanescent field, the symmetry plane of the image is inside the structure rather than the boundary. In addition, moving the PC by 2μm to the left horizontally, the image moves by 3.57μm, and the half-width of each image is less than the half of wavelength in this process.

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