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Accepted papers to appear in an upcoming issue

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High-performance chemical vapor deposited graphene-on-silicon nitride waveguide photodetectors

Yun Gao, guodong zhou, Ni Zhao, Hon Tsang, and Chester C.T. Shu

Doc ID: 318903 Received 03 Jan 2018; Accepted 16 Feb 2018; Posted 16 Feb 2018  View: PDF

Abstract: Waveguide photodetectors integrated with graphene have demonstrated potential for ultrafast response and broadband operation. Here, we demonstrate high-performance chemical vapor deposited graphene-on-silicon nitride waveguide photodetectors by enhancing the absorption of light propagating in the transverse-magnetic mode through a metal-graphene junction. A doubling in responsivity is experimentally observed. In our zero-biased metal-graphene junction, a 15 mA W¯¹ intrinsic responsivity and a 30 GHz bandwidth are achieved at ~1550 nm. The results are comparable to those obtained from the best pristine graphene-based photodetectors. Our work enables new architectures for high-performance optoelectronic devices based on the graphene-on-silicon nitride platform.

Single stage MHz mid-IR OPA using LiGaS2 and a fiber laser pump source

Samuel Penwell, Lukas Whaley-Mayda, and Andrei Tokmakoff

Doc ID: 319555 Received 16 Jan 2018; Accepted 15 Feb 2018; Posted 16 Feb 2018  View: PDF

Abstract: We present the design and characterization of a tunable mid-IR optical parametric amplifier (OPA) with a 1 MHz 1033 nm fiber laser pump source. The OPA generates >10 nJ/pulse tunable from 3-7.5 μm with 85-165 cm-1 bandwidth and 140-540 fs pulse durations. The design utilizes a single stage of collinear, Type I amplification in lithium gallium sulfide (LGS) seeded by the near-IR portion of a super-continuum (SC) generated in yttrium aluminum garnet (YAG). The resulting mid-IR idler beam is isolated as the output. This single stage OPA is a simple and convenient source of high repetition rate, tunable mid-IR radiation for high throughput ultrafast infrared spectroscopy.

Spatially resolved standoff trace chemical sensing using backwards transient absorption spectroscopy

Fedor Rudakov, Joseph Geiser, and Peter Weber

Doc ID: 320184 Received 25 Jan 2018; Accepted 15 Feb 2018; Posted 15 Feb 2018  View: PDF

Abstract: A technique for the spatially resolved and molecule-specific detection of chemical vapors is presented. The chemical specificity arises from a transient absorption spectrum where an ultraviolet pulse excites the molecule to a Rydberg state, and a near infrared or visible probe pulse records a transient absorption spectrum. By recording the NIR pulse reflected off a random, distant object and measuring the elapsed time between emission of the UV pulse and the absorption of a counter-propagating NIR pulse, the distance to the absorber is obtained. The feasibility of the approach is demonstrated by detecting acetone plumes with millimeter spatial resolution.

1.5μm PM dual-wavelength single-frequency DBR fiber laser with 28 GHz stable frequency difference

Yubin Hou, Shuxian Qi, Xian Feng, Pu Wang, and Qian Zhang

Doc ID: 318023 Received 20 Dec 2017; Accepted 15 Feb 2018; Posted 16 Feb 2018  View: PDF

Abstract: We demonstrate a polarization maintaining (PM) dual-wavelength (DW) single-frequency Er-doped distributed Bragg reflection (DBR) fiber laser with 28 GHz stable frequency difference. A home-made PM low reflectivity superimposed fiber Bragg grating (SFBG) is employed as the output port of the DBR fiber laser. The SFBG has two reflection wavelengths located in the same gating region. The reflectivity of both DWs is around 85%. The achieved linear polarization extinction ratio is more than 20 dB. The DWs of the laser output are located at 1552.2 nm and 1552.43 nm, respectively. The optical signal-to-noise ratio (OSNR) is above 60 dB. For each wavelength only one longitudinal mode exists. The beat frequency of the two longitudinal modes is measured to be 28.4474 GHz, with the signal-to-noise ratio (SNR) of more than 65dB and the linewidth less than 300 Hz. During a 60-minute-long measurement, the standard deviation of the frequency fluctuation is 58.592 kHz.

Single-frequency fiber laser based on fiber ring resonator filter tunable in a broad range from 10 nm to 1107 nm

Pavel Honzatko, Yauhen Baravets, and Ashwin Myakalwar

Doc ID: 318107 Received 20 Dec 2017; Accepted 15 Feb 2018; Posted 15 Feb 2018  View: PDF

Abstract: We present a broadly tunable single-frequency ytterbium-doped fiber laser. Its broadband tunability is made possible by low resonator losses. The wavelength is determined by a grating filter while the single-frequency regime is achieved by filtering the longitudinal modes in a fiber ring resonance filter. We obtained a tuning range from 1027 nm to 1107 nm. A feedback loop driving a fiber stretcher actuated by a piezo-element prevents mode-hopping whenever the target frequency is reached. Based on the coherent delayed self-heterodyne interferometry, the laser linewidth is estimated to be 1.2 kHz with feedback open and 13.7 kHz with feedback closed.

Diode-pumped femtosecond Tm3+-doped LuScO₃ laser near 2.1 μm

Neil Stevenson, Tom Brown, John-Mark Hopkins, Martin D. Dawson, Christian Kraenkel, and Alexander Lagatsky

Doc ID: 309226 Received 21 Dec 2017; Accepted 14 Feb 2018; Posted 15 Feb 2018  View: PDF

Abstract: We report on the first demonstration of a diode-pumped Tm:LuScO₃ laser. Efficient and broadly tunable continuous wave operation in the 1973 – 2141 nm region and femtosecond mode-locking through the use of an ion-implanted InGaAsSb quantum-well-based SESAM are realized. When mode-locked, near transform limited pulses as short as 170 fs were generated at 2093 nm with an average output power of 113 mW and a pulse repetition frequency of 115.2 MHz. Tunable picosecond pulse generation was demonstrated in the 2074 – 2104 nm spectral range.

Mid-IR broadband supercontinuum generation from a suspended silicon waveguide

Rai Kou, Taiki Hatakeyama, Jason Horng, Ji-Hun Kang, Yuan Wang, Xiang Zhang, and Feng Wang

Doc ID: 315728 Received 14 Dec 2017; Accepted 14 Feb 2018; Posted 16 Feb 2018  View: PDF

Abstract: Mid-infrared (Mid-IR) photonics is known for providing various advantages in scientific discoveries with new contributions to industrial applications. However, a wide-band and energy-efficient light generation was a long-standing bottleneck that limited the development at this wavelength range. In this paper, we propose an all-air-cladding silicon-rib waveguide to determine the nonlinear performance of supercontinuum generation (SC). By tuning the waveguide dispersion parameters with simulation, a continuous broad spectrum of 1.32 octave (2~5 μm) was observed with a pump pulse wavelength of 4 μm. To further investigate our device characteristics, multiple conditions were set by varying the interaction length, pump power and waveguide dimension, which revealed the nonlinear phenomenon in the waveguide.

Transverse Translation Diverse Phase Retrieval Using Soft-Edged Illumination

Aaron Michalko and James Fienup

Doc ID: 319971 Received 22 Jan 2018; Accepted 14 Feb 2018; Posted 15 Feb 2018  View: PDF

Abstract: Transverse Translation Diverse Phase Retrieval (TTDPR), a ptychographic image-based wavefront-sensing technique, is a viable method for optical shop testing due to its high accuracy and relatively simple experimental arrangement. However, when measuring a reflective optic, a normally hard-edged translating illumination will become soft-edged due to diffraction, which may reduce the accuracy of TTDPR by suppressing fine structures in measured data. In this letter, we quantitatively explore the wavefront-sensing accuracy of TTDPR in the presence of soft-edged translating illumination.

Experimental Investigations on the TMI Thresholds of Low-NA Yb-doped single mode fibers

Franz Beier, Friedrich Möller, Bettina Sattler, Johannes Nold, Andreas Liem, Christian Hupel, Stefan Kuhn, Sigrun Hein, Nicoletta Haarlammert, Thomas Schreiber, Ramona Eberhardt, and Andreas Tünnermann

Doc ID: 304107 Received 21 Dec 2017; Accepted 13 Feb 2018; Posted 15 Feb 2018  View: PDF

Abstract: In this contribution we investigate the transversal mode instability behavior of an ytterbium doped commercial 20/400 fiber and obtain 2.9 kW of output power after optimizing the influencing parameters. In this context, we evaluate the influence of the bend diameter and the pump wavelength within the scope of the absorption length and the length of the fiber. Furthermore with a newly developed fiber we report on 4.4 kW of single-mode output power at 40 cm bend diameter.

Colorimetric Detection of Ultrathin Dielectrics on Strong-Interference Coatings

Sencer Ayas, Gokhan Bakan, Erol Ozgur, Kemal Celebi, Gamze Torunoglu, and Aykutlu Dana

Doc ID: 319524 Received 12 Jan 2018; Accepted 13 Feb 2018; Posted 16 Feb 2018  View: PDF

Abstract: Metal films covered with ultrathin lossy dielectrics can exhibit strong-interference effects manifested as broad absorption of the incident light resulting in distinct surface colors. Despite its simple bilayer structure, such surfaces have only recently been scrutinized and applied mainly for color printing. Here, we report the use of such surfaces for colorimetric detection of ultrathin dielectrics. The peak absorbance redshifts upon deposition of a nanometer-thick dielectric, changing the surface color. The color contrast between the bare and dielectric-coated surfaces can be detected by the naked eye. The optical responses of the surfaces are characterized for nanometer-thick SiO₂, Al₂O₃, and as well as bovine serum albumin molecules. The results suggest that strong-interference surfaces can be employed as biosensors.

A femtosecond 8.5 μm source based on intrapulse difference-frequency generation of 2.1 μm pulses

Ondrej Novak, Peter Krogen, Tobias Kroh, Tomas Mocek, Franz Kaertner, and Kyung-Han Hong

Doc ID: 314734 Received 04 Dec 2017; Accepted 13 Feb 2018; Posted 13 Feb 2018  View: PDF

Abstract: We report on a femtosecond ~8.5 μm, ~2 μJ source based on the intrapulse difference-frequency generation (DFG) of 2.1 μm pulses in an AgGaSe₂ (AGSe) crystal. Compared to the conventional ~0.8 or 1 μm near-infrared (IR) pulses, a ~2 μm driver for intrapulse DFG can provide more efficient conversion into the wavelengths longer than 5 μm due to a lower quantum defect and is more suitable for the non-oxide nonlinear crystals that have a relatively low bandgap energy. Using 26 fs, 2.1 μm pulses for type-II intrapulse DFG we have generated intrinsically carrier-envelope phase-stable idler pulses with a conversion efficiency of ~1%, which covers the wavelength range of 7 – 11 μm. Our simulation study shows that the blueshift of intrapulse DFG is assisted by self-phase modulation of the driving pulses in AGSe. The idler pulses are particularly useful for strong-field experiments in nanostructures as well as for seeding parametric amplifiers in the long-wavelength IR.

Kramers-Kronig Detection with Brillouin Amplified Virtual Carrier

Qiulin Zhang, Bofang Zheng, and Chester C.T. Shu

Doc ID: 319317 Received 09 Jan 2018; Accepted 12 Feb 2018; Posted 13 Feb 2018  View: PDF

Abstract: We proposed a novel scheme for realizing Kramers-Kronig detection by utilizing the narrow-band and high gain characteristic of stimulated Brillouin scattering. At the receiver, the weak virtual carrier located at the edge of the signal spectrum is Brillouin amplified by the output of a slave laser, which is injection locked by a weak pump seed provided by the transmitter. More than 2.7 dB optical signal-to-noise ratio (OSNR) sensitivity improvement is experimentally obtained compared with the traditional virtual carrier assisted scheme after a 80 km transmission. The effective number of bits (ENOB) requirement and the performance gain in nonlinear transmission are both analyzed by simulation.

Cavity enhanced DUV laser for two-photon cooling of atomic hydrogen

Samuel Cooper, Zakary Burkley, Adam Brandt, Cory` Rasor, and Dylan Yost

Doc ID: 319135 Received 11 Jan 2018; Accepted 12 Feb 2018; Posted 12 Feb 2018  View: PDF

Abstract: We demonstrate a 650 mW 243 nm continuous-wave laser coupled to a linear optical enhancement cavity. The enhancement cavity can maintain >30W of intracavity power for >1 hour of continuous operation without degradation. This system has sufficient power for a demonstration of two-photon laser cooling of hydrogen and may be useful for experiments on other simple two-body atomic systems.

Compact sub-kHz low-frequency quantum light source based on four-wave mixing in cesium vapor

Rong Ma, Wei Liu, Zhongzhong Qin, Xiaolong Su, Xiaojun Jia, junxiang zhang, and Jiangrui Gao

Doc ID: 319583 Received 11 Jan 2018; Accepted 12 Feb 2018; Posted 12 Feb 2018  View: PDF

Abstract: Using a nondegenerate four-wave mixing (FWM) process based on a double-Λ scheme in hot cesium vapor, we demonstrate a compact diode-laser-pumped quantum light source for the generation of quantum correlatedtwin beams with a maximum squeezing of 6.5 dB. The squeezing is observed at a Fourier frequency in the audio band down to 0.7 kHz, which is the first observation of sub-kHz intensity-difference squeezing in an atomic system so far. Phase-matching condition is also investigated in our system, which confirms the spatial multi-mode characteristics of the FWM process. Ourcompact low-frequency squeezed light source may find applications in quantum imaging, quantum metrology, and the transfer of optical squeezing onto matter wave.

2.1 μm composite Tm/Ho: YAG laser

Haizhou Huang, Huang Jianhong, yan ge, hui zheng, wen weng, Hongchun Wu, and Wenxiong Lin

Doc ID: 320740 Received 26 Jan 2018; Accepted 12 Feb 2018; Posted 13 Feb 2018  View: PDF

Abstract: We realize Ho laser operation in a composite Tm/Ho:YAG gain medium for the first time, which was integrated via diffusion bonding the Tm-doped and Ho-doped crystals into a single bulk structure. Maximum output power around 6 W was obtained with slope efficiency of 40.1% and conversion efficiency (CE) of 33.6% from the absorbed 785 nm diode laser to 2122 nm Ho laser, which is comparable with CE in 1.9 μm LD pumped Ho lasers. Such scheme is demonstrated to be another valid way for Ho laser generation here, which is of significance to be adopted in other host media or waveguide structures for an assessable, compact and efficient Ho laser.

A nonvolatile tunable SiC-based mid-infrared thermal emitter enabled by phase-changing materials

Lu Cai, Kaikai Du, Yurui Qu, Hao Luo, Meiyan Pan, Min Qiu, and Qiang Li

Doc ID: 317958 Received 27 Dec 2017; Accepted 12 Feb 2018; Posted 15 Feb 2018  View: PDF

Abstract: Polar crystals can enable strong light–matter interaction at infrared regime and provide many practical applications including thermal emission. However, the dynamic control of thermal emission based on polar crystals remains elusive as the lattice vibrations are solely determined by the crystal structure. Here, a nonvolatile tunable mid-infrared thermal emitter enabled by a phase-changing film Ge₂Sb₂Te₅ on silicon carbide polar crystal is demonstrated. By controlling the state of GST from amorphous to crystalline state, the emissivity of the thermal emitter is tuned from a low value to near-unity with a maximum change in peak emissivity of exceeding 10 dB over the Reststrahlen band of SiC (11.4 to 12.3 μm). This nonvolatile tunable thermal emitter, which presents a lot of advantages in terms of tunability, zero-static-power, angular insensitivity, and ease-of-fabrication, can be potentially applied for light sources, infrared camouflage and radiative cooling devices.

Thin-disk oscillator delivering radially polarized beams with up to 980 W of CW output power

Tom Dietrich, Martin Rumpel, Frieder Beirow, Cherry May Mateo, Christof Pruss, Wolfgang Osten, Marwan Abdou Ahmed, and Thomas Graf

Doc ID: 321200 Received 01 Feb 2018; Accepted 12 Feb 2018; Posted 15 Feb 2018  View: PDF

Abstract: We report on the generation of kW-class continuouswave radially polarized laser radiation in an Yb:LuAG thin-disk laser (TDL). Output powers of up to 980 W were achieved with an optical efficiency of 50.5% with respect to the incident pump power of the TDL. The degree of radial polarization was measured to be 95.5% at maximum output power. This was achieved by theintegration of a new generation of broadband, large-area grating-waveguide mirror with unprecedented high polarization discrimination as the end-mirror in the TDL resonator.

70 Femtosecond Kerr-lens mode-locked multipass-cavity Alexandrite laser

Can Cihan, Abdullah Muti, Isinsu Baylam, askin kocabas, Umit Demirbas, and Alphan Sennaroglu

Doc ID: 320866 Received 30 Jan 2018; Accepted 11 Feb 2018; Posted 16 Feb 2018  View: PDF

Abstract: We report to the best of our knowledge, the shortest femtosecond pulses generated from a Kerr-lens mode-locked Alexandrite laser operating near 750 nm. The Alexandrite gain medium was pumped with a continuous-wave, 532-nm laser and the performance of both the short and extended resonators was investigated. The use of an extended cavity eliminated the multi-wavelength spectral instabilities observed during the continuous-wave operation of the short cavity. Furthermore, since the repetition rate of the Alexandrite laser was reduced from 107 to 5.6 MHz, the resulting increase in the intracavity pulse energy provided enhanced Kerr nonlinearity and eliminated the Q-switching instabilities during mode-locked operation. The Kerr-lens mode-locked MPC Alexandrite laser produced nearly transform-limited, 70-fs pulses at a pulse repetition rate of 5.6 MHz with only 1W of pump power. The time-bandwidth product was further measured to be 0.331.

Machine Learning for Improved Image-Based Wavefront Sensing

Scott Paine and James Fienup

Doc ID: 318741 Received 29 Dec 2017; Accepted 11 Feb 2018; Posted 12 Feb 2018  View: PDF

Abstract: For large amounts of wavefront error, gradient-based optimization methods for image-based wavefront sensing are unlikely to converge when the starting guess for the wavefront differs greatly from the true wavefront. We use machine learning operating on a point-spread function to determine a good initial estimate of the wavefront. We show that our trained convolutional neural network provides good initial estimates in the presence of detector noise and is more effective than using many random starting guesses for large amounts of wavefront error.

Terahertz radiation in graphene hyperbolic medium excited by an electric dipole

Xiaodong Feng, Sen Gong, Renbin Zhong, Tao Zhao, Min Hu, Chao Zhang, and Shenggang Liu

Doc ID: 315815 Received 18 Dec 2017; Accepted 11 Feb 2018; Posted 12 Feb 2018  View: PDF

Abstract: In this letter, the enhanced and directional radiation in a wide terahertz frequency range in graphene hyperbolic medium excited by an electric dipole is presented. The numerical simulations and theoretical analyses indicate that the enhanced radiation comes from the strong surface plasmons couplings in graphene hyperbolic medium, consisting of alternative graphene and dielectric substrate layers. The simulation results also show that the peak power flow of the enhanced THz radiation in graphene hyperbolic medium is dramatically enhanced by more than 1 order of magnitude than that in general medium within a certain distance from the dipole. And the electromagnetic fields are strongly concentrated in a narrow angle. Besides, the radiation fields can be manipulated and the fields’ angular distributions can be tuned by adjusting the dielectric permittivity and thickness of substrates, and the chemical potential of graphene. Accordingly, it provides a good opportunity for developing miniature, integratable, high-power-density, and tunable radiation sources in the terahertz band at room temperature.

Enhanced spin Hall effect of light by transmission in a polymer

Osamu Takayama and Graciana Puentes

Doc ID: 321342 Received 02 Feb 2018; Accepted 10 Feb 2018; Posted 15 Feb 2018  View: PDF

Abstract: We demonstrate experimentally the lateral circular birefringence of a tunable birefringent polymer, the first example of the spin Hall effect of light in a polymeric material, and we demonstrate that this light shift can be significantly enhanced by tuning the effective birefringence in the polymer. We report experimental observations of this effect using polarimetric techniques and quantum-weak-measurement techniques, reporting a weak amplification factor of 200.

All-fiber laser with flattop beams output using a few-mode fiber Bragg grating

Changlong Xu, Ke Yan, Chun Gu, Peijun Yao, Lixin Xu, and Qiwen Zhan

Doc ID: 320192 Received 22 Jan 2018; Accepted 09 Feb 2018; Posted 12 Feb 2018  View: PDF

Abstract: We report a novel method of beam shaping in all-fiber laser. Flattop beams are firstly generated from the all-fiber laser using a few-mode fiber Bragg grating by superposing the fundamental mode (LP01) with a solid central beam distribution and the second order mode (LP11) gives rise to a donut-shape beam distribution. Two modes are obtained in fiber laser simultaneously and the wavelengths of two modes are 1053.7 nm and 1055.4 nm, respectively. Experiment has been carried out and a high quality flattop profile is obtained for the normalized Root-Mean-Square (RMS) of the light intensity less than 5% under no numerical aperture illumination, which is consistent with the theoretical prediction.

Femtosecond two-photon-excited backward lasing of atomic hydrogen in a flame

PengJi Ding, Maria Ruchkina, liu yi, Marcus L.E. Alden, and Joakim Bood

Doc ID: 314310 Received 29 Dec 2017; Accepted 09 Feb 2018; Posted 09 Feb 2018  View: PDF

Abstract: We report on an observation of bi-directional 656 nm lasing action of atomic hydrogen in premixed CH₄/air flame induced by resonant femtosecond 205 nm two-photon excitation. In particular, the backward-propagating lasing pulse is characterized in the spatial and temporal domains for the sake of single-ended diagnostic. Its picosecond-scale duration and smooth temporal profile enable spatially-resolved detection of hydrogen atoms in the millimeter range, which is successfully demonstrated using two narrow welding flames.

8 µm luminescence from a Tb3+ GaGeSbSe fiber

Florent Starecki, Nora Abdellaoui, Alain BRAUD, Jean-Louis DOUALAN, Catherine Boussard-Pledel, Bruno Bureau, Patrice Camy, and Virginie Nazabal

Doc ID: 315194 Received 08 Dec 2017; Accepted 09 Feb 2018; Posted 12 Feb 2018  View: PDF

Abstract: In this letter, we report for the first time on an emission at 8µm from Tb3+ doped Ga₅Ge₂₀Sb₁₀Se₆₅ chalcogenide fibers with doping levels at 1000 ppm and 500 ppm. These fibers were drawn following conventional melt-quenching methods and pumped at 2.05 µm using a Tm3+:YAG laser. The spectroscopic properties of the emitting ⁷F₄ manifold are investigated in order to rule out any artefact. Time resolved spectroscopic experiments are presented to build a comprehensive study of this 8 µm fluorescence, recorded with a clear signal to noise ratio.

Optical trapping and micromanipulation with a photonic lantern mode multiplexer

Amado Velazquez-Benitez, K. Yanín GUERRA-SANTILLÁN, Raúl Caudillo-Viurquez, Jose Antonio-Lopez, Rodrigo Amezcua Correa, and Juan Hernandez-Cordero

Doc ID: 315227 Received 13 Dec 2017; Accepted 09 Feb 2018; Posted 12 Feb 2018  View: PDF

Abstract: We demonstrate a simple approach based on a photonic lantern spatial multiplexer and a few-mode fiber for optical trapping and manipulation of multiple microspheres. Selective generation of LP fiber modes provides light patterns useful for trapping one or multiple microparticles. Furthermore, rotation of the particles can be achieved by switching between degenerate LP modes, as well as through polarization rotation of the input light. Our results show that emerging fiber optic devices such as photonic lanterns can provide a versatile and compact means for developing optical fiber traps.

Obstacle evasion in free-space optical communications utilizing Airy beams

Guoxuan Zhu, Yuanhui Wen, Xiong Wu, Yujie Chen, Jie Liu, and Siyuan Yu

Doc ID: 320166 Received 18 Jan 2018; Accepted 08 Feb 2018; Posted 09 Feb 2018  View: PDF

Abstract: A high speed free-space optical communication system capable of self-bending signal transmission around line-of-sight obstacles is proposed and demonstrated. Airy beams are generated and controlled to achieve different propagating trajectories, and the signal transmission characteristics of these beams around the obstacle are investigated. Our results confirm that, by optimising their ballistic trajectories, Airy beams are able to bypass obstacles with more signal energy and thus improve the communication performance compared with normal Gaussian beams.

Generation of high-energy, kHz-rate narrowband tunable ultraviolet pulses using a burst-mode dye laser system

Rongchao Pan, Ulrich Retzer, Thomas Werblinski, Mikhail Slipchenko, Terrence Meyer, Lars Zigan, and Stefan Will

Doc ID: 318182 Received 21 Dec 2017; Accepted 08 Feb 2018; Posted 09 Feb 2018  View: PDF

Abstract: Typical commercial pulsed dye laser systems used in the generation of narrowband, tunable ultraviolet radiation for planar laser-induced fluorescence (PLIF) imaging are either optimized for high (~5–10 kHz) repetition rates at comparatively low ultraviolet pulse energies (100’s µJ) or high output pulse energies (>10 mJ) at comparatively low repetition rates (~10 Hz). In this work we use a frequency-doubled Nd:YAG burst-mode laser to pump a custom dye laser system for high pulse energies and repetition rates of 7.5, 10, and 20 kHz at 566 nm. The frequency-doubled output of over 2.2 mJ/pulse at 283 nm, which can be used for PLIF imaging of combustion radicals, is an order of magnitude higher per pulse energy as compared with continuously pulsed dye laser systems and is ~3× higher in overall efficiency than a burst-mode optical parametric oscillator (OPO) at similar wavelengths. The effects of repetition rate, pump energy, and dye concentration on the output conversion efficiency and pulse-to-pulse stability of the current system are discussed.

Enhanced laser conditioning of magnetorheologically finished silica using temporally shaped pulses

Kyle Kafka, Semyon Papernov, and Stavros Demos

Doc ID: 318308 Received 05 Jan 2018; Accepted 08 Feb 2018; Posted 12 Feb 2018  View: PDF

Abstract: Laser conditioning was investigated as a function of the temporal shape and duration of 351-nm, nanosecond pulses for fused-silica substrates polished via magnetorheological finishing. The aim is to advance our understanding of the dynamics involved to enable improved control of the interaction of laser light with the material to optimize laser conditioning. Gaussian pulses that are temporally truncated at the intensity peak are observed to enhance laser conditioning, in comparison to a Gaussian pulse shape.

Optimized inhibited-coupling Kagome fibers at Yb-Nd:Yag (8.5 dB/km) and Ti:Saph (30 dB/km) ranges

Martin Maurel, Matthieu Chafer, Abhilash Amsanpally, Muhammad Adnan, Foued Amrani, Benoît Debord, Luca Vincetti, Frédéric Gérôme, and Fetah Benabid

Doc ID: 315178 Received 07 Dec 2017; Accepted 08 Feb 2018; Posted 15 Feb 2018  View: PDF

Abstract: We report on the development of hypocycloid core-contour inhibited coupling Kagome HC-PCFs with record transmission loss and spectral coverage which include the common industrial laser wavelengths. Using the scaling of the confinement loss with the core-contour negative curvature and the silica strut thickness, we fabricated IC Kagome HC-PCF for Yb and Nd:Yag laser guidance with record loss level of 8.5 dB/km associated with a 225 nm wide 3-dB bandwidth. A second HC-PCF is fabricated with reduced silica strut thickness whilst keeping the hypocycloid core-contour. It exhibits a fundamental transmission window spanning down to the Ti:Sa spectral range, and with a loss figure of 30 dB/km at 750 nm. The fibers modal properties (S2 and PER) and bending sensitivity show these HC-PCFs to be ideal for ultra-low loss, flexible and robust laser beam delivery.

Ultrasound modulated laser confocal feedback imaging inside turbid media

Kaiyi Zhu, Yueyue Lu, Shulian Zhang, Haowen Ruan, Shin Usuki, and Yidong Tan

Doc ID: 318336 Received 26 Dec 2017; Accepted 07 Feb 2018; Posted 09 Feb 2018  View: PDF

Abstract: The ultrasound modulated laser confocal feedback technology is proposed in the imaging inside turbid media. By selecting the detectable signal photons and rejecting the background noise photons in the frequency domain based on the ultrasound modulation, the signal-to-noise ratio (SNR) can be much improved especially in the turbid media compared with the traditional imaging without ultrasound modulation. It is a promising method to reach both a larger penetration depth and a better SNR than other optical methods.

GeSn resonant-cavity-enhanced photodetectors on silicon-on-insulator platforms

Guo-En Chang, BO-JUN HUANG, JUN-HAN LIN, and Henry Cheng

Doc ID: 315503 Received 11 Dec 2017; Accepted 06 Feb 2018; Posted 09 Feb 2018  View: PDF

Abstract: We report GeSn p–i–n resonant-cavity-enhanced photodetectors (RCEPDs) grown on silicon-on-insulator (SOI) substrates. A vertical cavity, composed of a buried oxide as the bottom reflector and a deposited SiO2 layer on the top surface as the top reflector, is created for the GeSn p–i–n structure to enhance the light–matter interaction. The responsivity experiments demonstrate that the photodetection range is extended to 1820 nm, completely covering all the telecommunication bands, because of the introduction of 2.5% Sn in the photon-absorbing layer. In addition, the responsivity is significantly enhanced by the resonant cavity effects, and a responsivity of 0.376 A/W in the telecommunication C-band is achieved, which is significantly higher than that of conventional GeSn-basedPDs. These results demonstrate the feasibility of CMOS-compatible, high-responsivity GeSn-based PDs for short-wave infrared applications.

Adaptive Polarization-Difference Transient Imaging for Depth Estimation in Scattering Media

Rihui Wu, Adrian Jarabo, Jinli Suo, Feng Dai, YongDong Zhang, Qionghai Dai, and Diego Gutiererrea

Doc ID: 304600 Received 14 Aug 2017; Accepted 06 Feb 2018; Posted 07 Feb 2018  View: PDF

Abstract: Introducing polarization into transient imaging improves depth estimation in participating media, by discriminating reflective from scattered light transport, and calculating depth from the former component only. Previous works have leveraged this approach, under the assumption of uniform polarization properties. However, the orientation and intensity of polarization inside scattering media is non-uniform, both in the spatial and temporal domains. As a result of this simplifying assumption, the accuracy of the estimated depth worsens significantly as the optical thickness of the medium increases. In this letter, we introduce a novel adaptive polarization-difference method for transient imaging, taking into account the nonuniform nature of polarization in scattering media. Our results demonstrate a superior performance for impulse-based transient imaging over previous unpolarized or uniform approaches.

Generation of multifocal irradiance patterns by using complex Fresnel holograms

Omel Mendoza-Yero, Miguel Carbonell-Leal, Gladys Mínguez-Vega, and Jesus Lancis

Doc ID: 307632 Received 20 Sep 2017; Accepted 06 Feb 2018; Posted 07 Feb 2018  View: PDF

Abstract: We experimentally demonstrate Fresnel holograms able to produce multifocal irradiance patterns with micrometric spatial resolution. These holograms are assessed from the coherent sum of multiple Fresnel lenses. The utilized encoded technique guaranties full control over the reconstructed irradiance patterns due to an optimal codification of the amplitude and phase information of the resulting complex field. From a practical point of view, a phase-only spatial light modulator is used in a couple of experiments addressed to obtain two and three dimensional distributions of focal points to excite both linear and non-linear optical phenomena.

Flexible Metasurface Black Nickel with Stepped Nanopillars

Qinyu Qian, Ying Yan, and Chinhua Wang

Doc ID: 312757 Received 06 Nov 2017; Accepted 06 Feb 2018; Posted 07 Feb 2018  View: PDF

Abstract: We report on a monolithic, all-metallic and flexible metasurface perfect absorber (black nickel (Ni)) based on coupled Mie resonances originated from vertically stepped Ni nanopillars homoepitaxially grown on Ni substrate. Coupled Mie resonances are generated from Ni nanopillars with different sizes such that Mie resonances of the stepped two sets of Ni nanopillars occur complementarily at different wavelengths to realize polarization-independent broadband absorption over the entire visible wavelength band (400 nm - 760 nm) within an ultra-thin surface layer of totally 162 nm thick only. Two-step double-beam interference lithography and electroplating are utilized to fabricate the proposed monolithic metasurface with stepped Ni nanopillars array that can be arbitrarily bent and pressed. A black nickel metasurface is experimentally demonstrated in which an average polarization independent absorption of 0.972 (0.961, experiment) in the entire visible band is achieved and remains 0.838 (0.815, experiment) when the incident angle increases to 70°. The demonstrated black Ni metasurface structures thus suggests a

RF Signal Detection by a Tunable Optoelectronic Oscillator Based on PS-FBG

Xiuyou Han, Yuchen Shao, Ming Li, and Mingshan Zhao

Doc ID: 319228 Received 10 Jan 2018; Accepted 06 Feb 2018; Posted 08 Feb 2018  View: PDF

Abstract: The low power radio frequency (RF) signal detection is highly desired for many applications, ranging from wireless communication to radar system. A tunable optoelectronic oscillator (OEO) based on phase-shifted fiber Bragg grating (PS-FBG) for detecting low power RF signals is proposed and experimentally demonstrated. When the frequency of the input RF signal is matched with the potential oscillation mode of the OEO, it is detected and amplified. The frequency of the RF signal under detection can be estimated simultaneously by scanning the wavelength of the laser source. The RF signals from 1.5 to 5 GHz as low as -91 dBm are detected with a gain of about 10 dB, and the frequency is estimated with an error of ±100 MHz. The performance of the OEO system for detecting RF signal with different modulation rates is also investigated.

Lattice of C-points at intensity nulls

Sushanta Pal and Paramasivam Senthilkumaran

Doc ID: 318269 Received 21 Dec 2017; Accepted 06 Feb 2018; Posted 12 Feb 2018  View: PDF

Abstract: The dependence of fringe contrast on the state of polarization (SOP) can be altered when more than two beams interfere and it is possible to achieve high contrast fringes. We use a six-pinhole interferometer in which judicious choice (but not-unique) of SOPs for the interfering beams is made to realize lattice of C-points at intensity nulls. These dark C-points occur due to overlapping of singularities. These are not simply a minor variation of bright C-points in which the intensity dims to zero, but are poorly understood, unusual objects in their own right. A discussion on Stokes intensity degeneracy is presented. In the ellipticity distributions, it is shown that V-points occur at nulls whereas C-points occur at extrema. It is shown that destructive interference of two right (left) handed bright C-points can result in a left (right) handed dark C-point.

SOI based microwave photonic filter with narrowband and ultrahigh peak rejection

Xiaolong Liu, Yuan Yu, Haitao Tang, Xu Lu, Jianji Dong, and Xinliang Zhang

Doc ID: 318198 Received 21 Dec 2017; Accepted 06 Feb 2018; Posted 15 Feb 2018  View: PDF

Abstract: We propose and demonstrate a silicon-on-insulator (SOI) based widely tunable microwave photonic filter (MPF), which is implemented by using an under-coupled microring resonator (MRR) assisted by two cascaded tunable Mach-Zehnder interferometers (MZIs). In the experiment, the MPF achieves an ultrahigh peak rejection of exceeding 60 dB, a full width at half maximum bandwidth of 780 MHz and a frequency tuning range of 0-40 GHz even when the propagation loss of the MRR is 1.65 dB/cm. To the best of our knowledge, this MPF demonstrates ultrahigh peak rejection and narrow bandwidth simultaneously in SOI for the first time with MRR of such propagation loss and avoids using external electrical devices to improve the rejection.

High-sensitivity magnetic field sensor based on tapered two-mode fiber interference

Bing Sun, Fang Fang, Zuxing Zhang, Jing Xu, and Lin Zhang

Doc ID: 318832 Received 04 Jan 2018; Accepted 06 Feb 2018; Posted 15 Feb 2018  View: PDF

Abstract: A compact and temperature-insensitive fiber optic magnetic field sensors based on a tapered two-mode fiber (TTMF) sandwiched between two single-mode fibers has been proposed and demonstrated. The section of TTMF with a specifically designed transition region as an efficient tool to filter higher-order modes, then the uniform modal interferometer just involved with LP01 and LP02 modes is achieved. The transmission spectral characteristics and the magnetic response of the proposed sensors have been investigated. Experimental results show that a maximum sensitivity of 98 pm/Oe within a linear magnetic-field intensity ranging from 0 to 140 Oe can be achieved. Significantly, the temperature cross-sensitivity problem can be resolved owing to the lower thermal expansion coefficient of the TTMF. Finally, with its low insertion loss, compactness and ease of fabrication, the proposed sensor would find potential applications in the measurement of magnetic field.

Three-dimensional dynamic measurement of irregular stringy object using digital in-line holography

Longchao Yao, Jun Chen, Paul Sojka, Xuecheng Wu, and Kefa Cen

Doc ID: 319633 Received 12 Jan 2018; Accepted 06 Feb 2018; Posted 15 Feb 2018  View: PDF

Abstract: Dynamic stringy objects like liquid rims and ligaments are frequently observed in important applications like multiphase breakup of fuel droplets. We develop a new method based on digital in-line holography to automatically measure complicated stringy objects. A static spring mounted on a rotator is measured to validate the effectiveness and accuracy of the method. Sections are extracted along the skeleton of the spring in a depth-of-field extended image and then sized and located as individual particles using a hybrid method. Surface points of sections are stitched together to visualize the entire spring. Local thickness error smaller than 5.3% and z error smaller than 0 um are achieved. This method is applied to characterize the spatial-temporal features of the liquid rim formed in the bag-type regime of the aerodynamic breakup of a falling drop. The evolution of the rim/ligament structures is continuously captured in seven frames, lasting in 1.58 milliseconds. This work extends the application of digital holography as an effective 3D diagnostic tool.

Internal polarization dynamics of vector dissipative-soliton-resonance pulses in normal dispersion fiber lasers

Daojing Li, Deyuan SHEN, Lei Li, Dingyuan Tang, Lei Su, and Luming Zhao

Doc ID: 318668 Received 29 Dec 2017; Accepted 05 Feb 2018; Posted 05 Feb 2018  View: PDF

Abstract: Internal polarization dynamics of vector dissipative-soliton-resonance (DSR) pulses in a mode-locked fiber laser is investigated. By utilizing a waveplate-analyzer configuration to analyze the special structure of a DSR pulse, we find that polarization state is not uniform across a resonant dissipative soliton. Specifically, although the central plane wave of the resonant dissipative soliton acquires nearly a single fixed polarization, the dissipative fronts feature polarization states that are different and spatially varying. This distinct polarization distribution is maintained while the whole soliton extends with increasing gain. Numerical simulation further confirms the experimental observations.

Optical resonances in Kretschmann and Otto configurations

Yuriy Akimov

Doc ID: 319710 Received 16 Jan 2018; Accepted 05 Feb 2018; Posted 07 Feb 2018  View: PDF

Abstract: This Letter revises the resonance theory of Kretschmann and Otto configurations, where enhanced electromagnetic fields and strong reflectance dips observed under total internal reflection are conventionally attributed to the resonance on surface plasmon-polaritons, the subsystem eigenwaves supported by a single metal/dielectric interface. It demonstrates that the field enhancement and reflection decrease are in fact two independent physical phenomena that occur under different conditions. Moreover, neither of them coincides with the resonance on surface plasmon-polaritons that manifests in Kretschmann and Otto configurations through other distinct optical effect.

The Inverse Problem of Quartic Photonics

Thomas Mulkey, Jimmy Dillies, and Maxim Durach

Doc ID: 319805 Received 16 Jan 2018; Accepted 05 Feb 2018; Posted 07 Feb 2018  View: PDF

Abstract: We formulate and solve the inverse problem of quartic photonics, or photonics of metamaterials, whose k-surfaces (also known as iso-frequency surfaces or Fresnel surfaces) are quartic surfaces. This provides an approach to engineer the effective parameters of metamaterials starting from the desired plane waves. We apply our method to the design of the high-k limit of metamaterials, extreme non-reciprocity and complex bi-anisotropic media.

Direct Transfer of Pump Amplitude to Parametric Down-Converted Photons

Ali Anwar, Pravin Vaity, Chithrabhanu Perumangatt, and Ravindra Singh

Doc ID: 312552 Received 03 Nov 2017; Accepted 05 Feb 2018; Posted 05 Feb 2018  View: PDF

Abstract: In general, the spatial distribution of individual photons (signal or idler) generated by spontaneous parametric down-conversion (SPDC) does not evidently show any particular spatial mode structure because of their randomness in generation and the incoherent nature. Here, we numerically showed that all individual photons generated by SPDC process carry the transverse amplitude as that of the pump and then confirmed it experimentally. The pump amplitude is revealed in SPDC when individual photons are spatially filtered from the total SPDC distribution. This is observed simply by imaging the photons that are filtered using a minimum-sized aperture. Phase measurements showed that the observed mode distribution does not possess the transverse phase distribution as that of the pump.

Single phonon source based on a giant acoustic nonlinear effect

Kang Cai, Zi-Wen Pan, Rui-Xia Wang, Dong Ruan, Zhangqi Yin, and Gui Lu Long

Doc ID: 313695 Received 17 Nov 2017; Accepted 04 Feb 2018; Posted 05 Feb 2018  View: PDF

Abstract: We propose a single phonon source based on nitrogen-vacancy (NV) centers, which are located in a diamond phononic crystal resonator. The strain in the lattice would induce the coupling between the NV centers and the phonon mode. The strong coupling between the excited state of the NV centers and the phonon is realized by adding an optical laser driving. This four level NV centers system exhibits the coherent population trapping (CPT), and yields giant resonantly enhanced acoustic nonlinearities, with zero linear susceptibility. Based on this nonlinearity, the single phonon source can be realized. We numerically calculate $g^{(2)}(0)$ of the single phonon source. We discuss the effects of the thermal noise and the external driving strength.

Anomalous resonant reflection in a Fabry-Perot cavity filled with weakly scattering medium

Ye Hao, Wentao Gao, and Zhijun Sun

Doc ID: 313790 Received 17 Nov 2017; Accepted 04 Feb 2018; Posted 05 Feb 2018  View: PDF

Abstract: In this work, we fabricated a metallic Fabry-Perot cavity, filled with a weakly scattering medium of unsintered sol-gel silica, on a glass substrate. We found anomalous asymmetric resonance reflection spectra of this structure, besides the effects of scattering loss in cavity. The asymmetric reflection is shown to be dependent on the media on both sides of the cavity. It is thought that, as the weakly scattering medium locates between highly reflecting boundaries and the cavity length is far less than mean free path of light in the medium, light scattering in the medium is enhanced at the resonance conditions. And the scattering centers act as elementary sources emitting the scattered incoherent light to the outside of the cavity from its both ends. The asymmetric reflection is then resulted from lossy total internal reflection of the scattered light at one of the boundaries, which eventually leaks to the outside of the cavity with higher index, and contributes to the measured backside reflectance.

Quantitative evaluation of light-matter interaction parameters in organic single crystal microcavities

Takumi Nishimura, Kenichi Yamashita, Shun Takahashi, Takeshi Yamao, Shu Hotta, Hisao Yanagi, and Masaaki Nakayama

Doc ID: 320018 Received 18 Jan 2018; Accepted 04 Feb 2018; Posted 05 Feb 2018  View: PDF

Abstract: Investigation of physics on light-matter interaction and strong coupling formation in organic microcavities is important to characterize the device structure enabling efficient room-temperature polariton condensation. In this study we evaluate quantitatively the light-matter interaction parameters for three types of organic single crystal microcavities and discuss the effects of microcavity structures on the strong coupling formation. We have found that improvement in cavity quality factor causes reduction in the photon damping constant, which results in an increase in the Rabi splitting energy. Moreover, when we used a metal thin film as the cavity mirror, it was revealed that the exciton damping is considerably strong. These experimental findings are very useful to achieve low-threshold or electrically pumped organic polariton devices.

Novel high-brightness and high color purity red-emitting Ca3Lu(AlO)3(BO3)4:Eu3+ phosphors with internal quantum efficiency close to unity for near-UV-based white light-emitting diodes

Xiaoyong Huang, Shaoying Wang, Bin Li, Qi Sun, and Heng Guo

Doc ID: 319439 Received 11 Jan 2018; Accepted 04 Feb 2018; Posted 13 Feb 2018  View: PDF

Abstract: In this work, we reported on novel high-brightness Eu3+-activated Ca3Lu(AlO)3(BO3)4 (CLAB) red-emitting phosphors. Under 397 nm excitation, the CLAB:Eu3+ phosphors showed intense red emissions at around 621 nm with CIE chromaticity coordinates of (0.657, 0.343). The optimal doping concentration of Eu3+ ions was found to be 30 mol%, and the CLAB:0.3Eu3+ sample possessed high color purity of 93% and ultra-high internal quantum efficiency as great as 98.5%. Importantly, the CLAB:0.3Eu3+ also had good thermal stability. Finally, a white light-emitting diode (WLED) lamp with good color render index was fabricated by using a 395 nm ultraviolet chip and the phosphor blends of CLAB:0.3Eu3+ red-emitting phosphors, BaSrSiO4:Eu2+ green-emitting phosphors and BaMgAl10O7:Eu2+ blue-emitting phosphors.

Wavelength tunable polarizer based on layered black phosphorus on Si/SiO₂ substrate

Wanfu Shen, Chunguang Hu, Shuchun HUO, Zhaoyang Sun, Shuangqing Fan, Jing Liu, and Xiaotang Hu

Doc ID: 319572 Received 15 Jan 2018; Accepted 03 Feb 2018; Posted 05 Feb 2018  View: PDF

Abstract: We report on the both theoretical and experimental design of black phosphorus (BP)-based reflective polarizer on Si/SiO₂ substrate in visible range using Fabry-Perot cavities method. Thanks to the optical anisotropyof BP, a tunable polarization wavelength and high extinction ratio can be achieved via optimizing the thickness of BP. Using azimuth-dependent reflectance difference microscopy (ADRDM), we directly measured a huge optical anisotropy of 1.58, corresponding extinction ratio of ~9dB, from a 96nm BP on silicon substrate capped by 260nm thermal oxidized silicon at awavelength of 690nm for the first time. Our results not only provide a new route to design nanoscale polarizer based on anisotropic two dimensional (2D) materials, promoting the applications of 2D materials in integrated optoelectronics and system-on-chip, but also suggest a modulation technique for optical anisotropy by integrating BP film with cavities structures.

Development of molecular-selective differential interference contrast microscopy utilizing stimulated Raman scattering

Motohiro Banno, Takayuki Kondo, and Hiroharu Yui

Doc ID: 317981 Received 18 Dec 2017; Accepted 02 Feb 2018; Posted 02 Feb 2018  View: PDF

Abstract: Development of a differential interference contrast (DIC) stimulated Raman scattering (SRS) microscope is presented. In the apparatus, coherent SRS signal generated from the sample is overlapped with a reference beam which is also focused on the same sample. The signal intensity correlates with the height difference between the point generating the SRS signal and the focal point of the reference beam. We applied the developed apparatus for imaging of Si surfaces with structures with the heights of 50 to 350 nm. We also obtained the DIC-SRS image of the Si surface buried by liquid crystal. The structures of the interface between Si and liquid crystal were well observed when both the SRS signals due to Si and liquid crystal were utilized. It is also revealed that DIC-SRS microscopy is an effective tool to obtain molecular-selective images of structured interfaces with the height of less than several tens of nanometers buried by optically transparent media.

Spatially-resolved control of fictitious magnetic fields in coldatomic ensemble

Adam Leszczynski, Mateusz Mazelanik, Michal Lipka, Michal Parniak, Michal Dabrowski, and Wojciech Wasilewski

Doc ID: 318083 Received 21 Dec 2017; Accepted 02 Feb 2018; Posted 02 Feb 2018  View: PDF

Abstract: Effective and unrestricted engineering of atom-photon interactions requires precise spatially-resolved control of light beams. The significant potential of such manipulations lies in a set of disciplines ranging from solid state to atomic physics. Here we use a Zeeman-like ac-Stark shift of a shaped laser beam to perform rotations of spins with spatial resolution in a large ensemble of cold rubidium atoms. We show that inhomogeneities of light intensity are the main source of dephasing and thus decoherence, yet with proper beam shaping this deleterious effect is strongly mitigated allowing rotations of 15 rad within one spin-precession lifetime. Finally, as a particular example of a complex manipulation enabled by our scheme, we demonstrate a range of collapse-and-revival behaviours of a free-induction decay signal by imprinting comb-like patterns on the atomic ensemble.

Generation of colorful Airy beams and Airy letters through two-photon processed cubic phase plates

Ze Cai, Ya Liu, Yanlei Hu, Chenchu Zhang, Jiangchuan Xu, Shengyun Ji, Jincheng Ni, Zhaoxin Lao, Jiawen Li, Yang Zhao, Dong Wu, and Jiaru Chu

Doc ID: 318963 Received 04 Jan 2018; Accepted 02 Feb 2018; Posted 02 Feb 2018  View: PDF

Abstract: In this letter, we demonstrate the observation of colorful Airy beams and Airy imaging of letters, which we called Airy letters here, generated through the continuous cubic phase microplate (CCPP) elaborately fabricated by femtosecond laser two-photon processing (TPP). The fabricated CCPP with both micro size (60 μm × 60 μm × 1.1 μm) and continuous variation of phase shows a good agreement with the designed one. Chromatic Airy beams and Airy letters “USTC” are experimentally generated via the CCPP illuminated by white light. In addition, superior properties of Airy letters are explored, which demonstrates that the Airy letters inherit the nondiffraction, self-healing and transverse acceleration characteristics of Airy beams. Our work paves the way towards integrated optics, light separation, optical imaging and defective information recovery.

Toward a compact fibered squeezed parametric source

alexandre brieussel, Konstantin Ott, Maxime Joos, Nicolas Treps, and Claude Fabre

Doc ID: 320327 Received 30 Jan 2018; Accepted 01 Feb 2018; Posted 08 Feb 2018  View: PDF

Abstract: In this work, we investigate three different compact fibered systems generating vacuum squeezing that involve optical cavities limited by the end surface of a fiber and by a curved mirror and containing a thin parametric crystal. These systems have the advantage to couple squeezed states directly to a fiber, allowing the user to benefit from fiber flexibility in the use of squeezing. Three types of fibers are investigated: standard single mode fibers, photonic crystal large mode area single mode fibers and short multimode fiber taped to a single mode fiber. The observed squeezing is modest (-0.56 dB,-0.9 dB,-1 dB), but these experiments open the way to miniaturized squeezing devices that could be a very interesting advantage in scaling up quantum systems for quantum processing, opening new perspectives in the domain of integrated quantum optics.

20-kHz CH2O and OH PLIF with stereo PIV

Stephen Hammack, Campbell Carter, Aaron Skiba, Christopher Fugger, Josef Felver, Joseph Miller, James Gord, and Tonghun Lee

Doc ID: 309216 Received 21 Nov 2017; Accepted 31 Jan 2018; Posted 01 Feb 2018  View: PDF

Abstract: Planar laser-induced fluorescence (PLIF) of hydroxyl and formaldehyde radicals was performed alongside stereo particle image velocimetry (PIV) at a 20-kHz repetition rate in a highly-turbulent piloted premixed Bunsen flame. A dual-pulse burst-mode laser generated envelopes of 532-nm pulse pairs for PIV as well as a pair of 355-nm pulses, the first of which was used for formaldehyde PLIF. A diode-pumped solid-state Nd:YAG/dye-laser system produced the ultraviolet excitation laser beam for hydroxyl PLIF. The combined diagnostics produced simultaneous, temporally resolved, two-dimensional fields of hydroxyl and formaldehyde radicals and two-dimensional three-component velocity fields, facilitating the observation of the interaction of fluid dynamics with flame fronts and preheat layers. The high-fidelity data acquired surpasses the state-of-the-art heretofore and is a demonstration of new dual-pulse burst-mode laser technology with the ability to provide pulse pairs at both 532 nm and 355 nm with sufficient energy for scattering and fluorescence measurement at 20 kHz.

Femtosecond laser direct writing of ion exchangeable multifunctional microstructures

Huan Wang, Yonglai Zhang, Rong Zhu, Dong-Lin Chen, Guang-Xin Jin, and Hong-Bo Sun

Doc ID: 314775 Received 05 Dec 2017; Accepted 31 Jan 2018; Posted 01 Feb 2018  View: PDF

Abstract: We report here the fabrication of ion exchangeable microstructures by femtosecond laser direct writing (FsLDW) of an ion exchange photopolymer, poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAMPS). The resultant microstructures are negatively charged in aqueous solution, and can adsorb positively charged species, such as metal ions, nanoparticles, and proteins by electrostatic interaction, forming functional components for chip functionalization. In addition, it is possible to modify the microstructures with positively charged species that make the microstructures sensitive to negatively charged species. As a typical example, a crossed 3D microvessel functionalized with antibodies was fabricated, which reveals great potential for organ-on-a-chip systems. The fabrication of ion exchangeable microstructures holds great promise for flexible chip functionalization.

Miniature probe for in vivo optical- and acoustic-resolution photoacoustic microscopy

Zhendong Guo, Yao Li, and Sung-Liang Chen

Doc ID: 313981 Received 21 Nov 2017; Accepted 31 Jan 2018; Posted 02 Feb 2018  View: PDF

Abstract: We present a miniature probe capable of both optical-resolution (OR) and acoustic-resolution (AR) photoacoustic microscopy. A gradient-index-lens fiber and a multi-mode fiber are used to deliver light for OR and AR illumination, respectively. The probe achieves lateral resolution of 3.1 µm for OR mode and 46-249 µm (at depth of 1.2-4.3 mm) for AR mode, respectively. The size of the probe attains 3.7 mm in diameter, which can be used for endoscopic applications. In vivo imaging of several different parts of a mouse demonstrates the excellent imaging ability of the probe.

Silicon arrayed waveguide gratings at 2.0-μm wavelength characterized with an on-chip resonator

Eric Stanton, Nicolas Volet, and John Bowers

Doc ID: 314760 Received 01 Dec 2017; Accepted 30 Jan 2018; Posted 02 Feb 2018  View: PDF

Abstract: Low-loss arrayed waveguide gratings (AWGs) are demonstrated at 2.0-µm wavelength. These devices promote rapidly developing photonic applications, supported by the recent development of mid-infrared lasers integrated on silicon (Si). Multi-spectral photonic integrated circuits at 2.0-µm are envisioned since the AWGs are fabricated with the 500-nm thick Si-on-insulator platform, compatible with recently demonstrated lasers and semiconductor optical amplifiers on Si. Characterization with the AWG-ring method improves the on-chip transmission uncertainty to ∼6 % compared to the conventional method with an uncertainty of ∼53 %. Channel losses of ∼2.4 dB are found, with−31 dB crosstalk per channel. Fully integrated multi-spectral sources at 2.0 µm, with pump lasers, low-loss multiplexers, modulators, and an output amplifier are now feasible.

Laser wakefield acceleration with mid-IR laser pulses

Daniel Woodbury, Linus Feder, Valentina Shumakova, Claudia Gollner, Robert Schwartz, Bo Miao, Fatholah Salehi, Anastasia Korolov, Audrius Pugzlys, Andrius Baltuska, and Howard Milchberg

Doc ID: 319889 Received 16 Jan 2018; Accepted 30 Jan 2018; Posted 01 Feb 2018  View: PDF

Abstract: We report on the first results of laser plasma wakefield acceleration driven by ultrashort mid-infrared laser pulses (λ= 3.9 μm, 100 fs, 0.25 TW), which enable near- and above-critical density interactions with moderate-density gas jets. Relativistic electron acceleration up to ~12 MeV occurs when the jet width exceeds the threshold scale length for relativistic self-focusing. We present scaling trends in the accelerated beam profiles, charge and spectra, which are supported by particle-in-cell simulations and time-resolved images of the interaction. For similarly scaled conditions, we observe significant increases in accelerated charge compared to previous experiments with near-infrared (λ=800 nm) pulses

Nonlinear characterisation of a silicon integrated Bragg waveguide filter

Micol Previde Massara, Matteo Menotti, Nicola Bergamasco, Nicholas Harris, Tom Baehr-Jones, Michael Hochberg, Christophe Galland, Marco Liscidini, Matteo Galli, and Daniele Bajoni

Doc ID: 318299 Received 09 Jan 2018; Accepted 30 Jan 2018; Posted 31 Jan 2018  View: PDF

Abstract: Bragg waveguides are promising optical filters for pump suppression in spontaneous Four-Wave Mixing (FWM) photon sources. In this work, we investigate the generation of unwanted photon pairs in the filter itself. We do this by taking advantage of the relation between spontaneous and classical FWM, which allows for the precise characterisation of the nonlinear response of the device. The pair generation rate estimated from the classical measurement is compared with the theoretical value calculated by means of a full quantum model of the filter, which also allows to investigate the spectral properties of the generated pairs. We find a good agreement between theory and experiment, confirming that stimulated FWM is a valuable approach to characterise the nonlinear response of an integrated filter, and that the pairs generated in a Bragg waveguide are not a serious issue for the operation of a fully integrated nonclassical source.

Toward real-time volumetric tomography for combustion diagnostics via dimension reduction

Tao Yu, Hecong Liu, Jiaqi Zhang, and Weiwei Cai

Doc ID: 313404 Received 17 Nov 2017; Accepted 29 Jan 2018; Posted 31 Jan 2018  View: PDF

Abstract: Volumetric tomography for combustion diagnostics is experiencing a significant progress during the past a few years due to its capability of imaging evolving turbulent flows. Such capability facilitates the understanding of the mechanisms behind complicated combustion phenomena such as lean blowout, acoustic oscillations, and formation of soot particles. However, these techniques are not flawless and suffer from high computational cost which prevents them from applications where real-time reconstructions and online monitoring are necessary. In this work, we propose a new reconstruction method that can effectively reduce the dimension of the inversion problem, which can then be solved with a minimum computational effort. This method along with a classical iterative method were tested against each other using a proof-of-concept experiment in which endoscopic computed tomography of chemiluminescence (CTC) was implemented. The results show that the proposed method can dramatically reduce the computational time and at the same time maintain similar reconstruction accuracy as opposed to the classical approach. Although this work was discussed under the context of CTC, it can be applied universally to other modalities of volumetric tomography such as volumetric laser-induced fluorescence.

Surface mode with large field enhancement in dielectric-dimer-on-mirror structures

Xianyu Ao

Doc ID: 314398 Received 27 Nov 2017; Accepted 29 Jan 2018; Posted 30 Jan 2018  View: PDF

Abstract: Plasmonic nanostructures with accessible and strongly enhanced fields are useful for a variety of applications related to surface-enhanced light-matter interaction. We describe a method to migrate localized fields from metal to dielectric surface. By arranging low-index contrast dielectric dimers on an optically thick metal film, a narrow-linewidth resonant mode is formed through diffraction coupling, with accessible enhancement away from metal surface. The enhancement in the electric field intensity is over 2000 by dielectric dimers with 100 nm gap and 720 nm period, and the resonant linewidth is about 0.35 nm around the wavelength of 725 nm. The dispersion of this periodic structure allows resonant enhancement of not only emission but also absorption. The design principle provides a means to tune the narrow-linewidth resonance over a wide wavelength range from ultraviolet to near infrared.

Single-shot coded aperture structured illumination digital holographic microscopy for superresolution imaging

Chau-Jern Cheng, Xin-Ji Lai, Yu-Chih Lin, and Han-Yen Tu

Doc ID: 314987 Received 06 Dec 2017; Accepted 29 Jan 2018; Posted 02 Feb 2018  View: PDF

Abstract: This paper proposes a coded aperture structured illumination (CASI) technique for one-shot acquisition in digital holographic microscopy (DHM). A CASI wave is generated using two binary phase codes (0° and 120°) for spatial phase shifting. The generated CASI wave then interferes with a reference wave to form a coded Fresnel hologram at a single exposure with compressive sensing (CS) to avoid the time-multiplexing structured illumination (SI) process. The CS algorithm is applied to retrieve the missing data of decoded phase-shifted SI modulated waves, which are used to separate overlapped spatial frequencies for obtaining a larger spatial frequency coverage to provide superresolution imaging. Two phase-only spatial light modulators are applied to generate an SI pattern for obtaining a coded aperture with a suitable size to perform one-shot acquisition in the DHM system.

NALM-based bismuth doped fiber laser at 1.7 µm

Aleksandr Khegai, Mikhail Melkumov, Vladimir Khopin, Konstantin Riumkin, Sergey Firstov, and Evgeny Dianov

Doc ID: 307526 Received 21 Sep 2017; Accepted 29 Jan 2018; Posted 29 Jan 2018  View: PDF

Abstract: We demonstrate, to our knowledge, the first bismuth doped fiber laser operating at 1.7 μm mode-locked by means of the Kerr nonlinearity. The laser setup has a figure-of-eight all-fiber design and yields 17 ps pulses with the 3.57 MHz repetition rate and the energy of 84 pJ. Using MOPA scheme with bismuth fiber amplifier the output pulse energy of 5.7 nJ was achieved. The further pulse compression in the fiber compressor shortened pulses to 630 fs. Operation of the master oscillator was modeled using nonlinear Schrödinger equation. Calculated data are in good agreement with experimental results.

Dual-band unidirectional forward scattering with all-dielectric hollow nanodisk in the visible

Xiao Ming Zhang, Qiang Zhang, Shangjie Zeng, Jun Jun Xiao, and Zhenzhen Liu

Doc ID: 314740 Received 01 Dec 2017; Accepted 29 Jan 2018; Posted 15 Feb 2018  View: PDF

Abstract: High-index dielectric nanoantennas have become an emerging branch of optical nanoantenna essentially due to their low loss. This kind of nanoantennas can achieve both forward and backward unidirectional scattering, enabled by electric dipole and magnetic dipole interaction. Here, we show that the scattering directionality can be further enhanced if higher-order moments are properly balanced and reach the generalized Kerker condition at two different wavelengths in an all-dielectric hollow nanodisk. Moreover, putting the nanodisks in an array of transverse configuration can enhance the unidirectionality to be needle-like, with main lobe angular beam width . Finally, we show that such unidirectional radiation properties can maintain for a local electric dipole source.

Effect of Soot Self-absorption on Color-ratio Pyrometry in Laminar Coflow Diffusion Flames

Nathan Kempema and Marshall Long

Doc ID: 315712 Received 15 Dec 2017; Accepted 28 Jan 2018; Posted 29 Jan 2018  View: PDF

Abstract: This Letter reports on the effect of self-absorption on measured temperature for color-ratio soot pyrometry with a color camera. A series of increasingly nitrogen diluted atmospheric pressure ethylene/air laminar coflow diffusion flames are studied, providing flames with different optical path lengths, soot loading, and soot optical properties. Numerical calculations are used to simulate the change in collected flame emission signal with and without light attenuation using experimentally measured maps of the soot absorption coefficient. This parameter implicitly contains information about soot volume fraction and soot optical properties. The ratio of these calculations is used to correct the raw color-channel signals, resulting in temperature maps with improved accuracy. The change in calculated temperature varies spatially within each flame, with the maximum correction quantified to be 22 K for a flame with a maximum optical depth of 0.31. This correction is as much as 42 K and 75 K for simulated flames with the same optical properties, structure, and a factor of two and five increase in soot volume fraction, respectively.

Tailorable chiral optical response through coupling among plasmonic meta-atoms with distinct shapes

Song Yue, Song Liu, Yu Hou, and Zichen Zhang

Doc ID: 319077 Received 05 Jan 2018; Accepted 26 Jan 2018; Posted 30 Jan 2018  View: PDF

Abstract: Chiral plasmonic nanostructures with giant and tunable chiral optical response holds great potential in chiral sensing applications for chemistry, biology, and pharmacy, etc. For the origin of chiral optical response of artificial plasmonic chiral assemblies, resonant and off-resonant coupling mechanisms have been figured out. However, most existing chiral plasmonic assemblies are based on only one mechanism, where strong optical chirality always compromises with spectral tunability. To release the trade-off between the strength and spectral tunability, we employ combination of resonant and off-resonant coupling mechanisms and demonstrate pronounced and tailorable chiral optical response based on plasmonic meta-atoms with distinct shapes. We anticipate that our strategy provides more flexibility in designing chiral plamsonic nanostructures and promote the field further towards customized chiral plasmonic platforms.

Passively Q-switched mid-infrared laser pulse generation with Au nanospheres as saturable absorber

Wenchao Duan, hongkun nie, Xiaoli Sun, Baitao Zhang, Guanbai He, Qi Yang, Haibing Xia, ruihua Wang, jie zhan, and Jingliang He

Doc ID: 319787 Received 15 Jan 2018; Accepted 26 Jan 2018; Posted 05 Feb 2018  View: PDF

Abstract: High quality Au nanospheres (Au-NPs) with a diameter of 52 nm were prepared by seeded growth method. Its mid-infrared (MIR) nonlinear saturable absorption properties were measured by balanced twin-detector measurement technique. With the as-prepared Au-NPs saturable absorber (SA), an efficient passively Q-switched (PQS) laser was realized at 2.95 μm for the first time, to the best of our knowledge. Under an absorbed pump power of 4.0 W, a maximum output power of 268 mW was obtained with the shortest pulse width of 734 ns and repetition rate of 91 kHz, corresponding to the pulse energy up to 2.95 µJ. The results indicate that Au-NPs are promising candidates as SAs for MIR laser pulse generation.

ACOUSTO-OPTIC TUNABLE SPECTRAL FILTRATION OF STEREOSCOPIC IMAGES

Vladislav Batshev, Alexander Machikhin, Vitold Pozhar, Alexey Gorevoy, and Alexander Naumov

Doc ID: 314303 Received 24 Nov 2017; Accepted 25 Jan 2018; Posted 29 Jan 2018  View: PDF

Abstract: We propose a new technique for three-dimensional (3-D) imaging in arbitrary spectral intervals. It is based on a simultaneous diffraction of two divergent stereoscopic light beams on a single acoustic wave propagating in a uniaxial birefringent crystal. We discuss in detail this configuration of acousto-optic (AO) interaction, derive basic relations and experimentally demonstrate the applicability of the proposed approach to 3-D spectral imaging. Stereo-imager of this type may be produced as an ultra-compact embeddable optical elements which are promising for many imaging applications.

Improved atmospheric effects elimination method for roughness estimation of painted surfaces

Ying Zhang, Jiabin Xuan, Huijie Zhao, Ping Song, Yi Zhang, and Wujian Xu

Doc ID: 315499 Received 12 Dec 2017; Accepted 25 Jan 2018; Posted 25 Jan 2018  View: PDF

Abstract: We propose a method for eliminating the atmospheric effect in polarimetric imaging remote sensing by using polarimetric imagers to simultaneously detect ground targets and skylight. Outdoor experiments are performed to obtain the polarimetric bidirectional reflectance distribution functions (pBRDFs) of painted surfaces and skylight under different weather conditions. Finally, the roughness of the painted surfaces is estimated. We find that the estimation accuracy with the proposed method is 6% on cloudy weather, while it is 30.72% without atmospheric-effect elimination. Our results prove that our method is effective for polarization remote sensing under complex weather condition.

Thermal stability of volume Bragg gratings in chloride photo-thermo-refractive glass after femtosecond laser bleaching

Dmitry Klyukin, Sergey Ivanov, Viktoria Krikova, Martti Silvennoinen, Yuri Svirko, and Nikolay Nikonorov

Doc ID: 313961 Received 22 Nov 2017; Accepted 25 Jan 2018; Posted 26 Jan 2018  View: PDF

Abstract: We demonstrate that the Joule heating of the volume Bragg grating recorded in chloride photo-thermo-refractive glass can be suppressed by bleaching of the silver nanoparticles with intense ultra-short laser pulses. Measurement of the bleached grating angular selectivity showed that at the signal wavelength at 972 nm, the spectral drift is 0.5 nm at the CW laser diode beam intensity of as high as 145 W/cm2. Thus the bleaching of silver nanoparticles results in the improved thermal stability of transmission gratings allowing one to employ them to control of the powerful CW laser radiation.

Compact CWDM interleaver based on an interfering loop containing a photonic crystal nanobeam cavity

Jiang Xinhong, Hongxia Zhang, Yong Zhang, Ciyuan Qiu, and Yikai Su

Doc ID: 314340 Received 01 Dec 2017; Accepted 25 Jan 2018; Posted 26 Jan 2018  View: PDF

Abstract: We propose and experimentally demonstrate a compact silicon photonic interleaver based on an interfering loop containing a photonic crystal nanobeam (PCN) cavity for coarse wavelength division multiplexing (CWDM) applications. The interleaver consists of a directional coupler and a PCN cavity designed to minimize the channel crosstalk. Instead of using an off-chip optical circulator, the reflection light of the interleaver can be separated from the input by placing two identical interleavers in a Mach-Zehnder interferometer (MZI) structure for practical applications. We also study the impacts of fabrication errors of the MZI structure. The fabricated device has a footprint of 64 μm × 70 μm and a channel spacing of ~19 nm. The maximum crosstalk is −16 dB in a wavelength range from 1508 nm to 1590 nm.

Power-flow-based design strategy for Bloch surface wave biosensors

Iterio Degli-Eredi, John Sipe, and Nathalie Vermeulen

Doc ID: 318133 Received 22 Dec 2017; Accepted 25 Jan 2018; Posted 26 Jan 2018  View: PDF

Abstract: We propose a novel semi-analytic design strategy for dielectric one dimensional multilayer biosensors, which is based on a relation between the angular sensitivity and the optical power flow of the Bloch Surface Wave guided by the multilayer. We show that our strategy can be used to optimise both the sensor's sensitivity and Figure-of-Merit without the need for extensive numerical parameter sweeps.

21 spatial modes erbium doped fiber amplifier for mode division multiplexing transmission

Zhenzhen Zhang, Cheng Guo, Liang Cui, Qi Mo, Ningbo Zhao, Cheng Du, Xiaoying Li, and Guifang Li

Doc ID: 314438 Received 28 Nov 2017; Accepted 24 Jan 2018; Posted 25 Jan 2018  View: PDF

Abstract: We experimentally demonstrate a 12 mode groups (21 spatial modes) cladding pumped few mode erbium doped fiber amplifier. The differential modal gain is dramatically reduced by using the double cladding erbium doped fiber (DC-EDF) with a refractive index trench structure, which helps to tightly confine all the 21 spatial modes in the core and to mitigate the bending loss. Our experimental results show the differential modal gain is about 3 dB when average signal modal gain for all 12 mode groups is up to 15 dB across the C band. Our method of using DC-EDF with a properly designed trench structure can be used to develop gain equalized few mode amplifiers supporting more spatial modes.

Optically powered radio-over-fiber system based on center- and offset-launching techniques using a conventional multimode fiber

Hayao Kuboki and Motoharu Matsuura

Doc ID: 314615 Received 29 Nov 2017; Accepted 24 Jan 2018; Posted 25 Jan 2018  View: PDF

Abstract: We have experimentally demonstrated radio-over-fiber (RoF) transmission with a 10-W feed power-over-fiber (PWoF) using a conventional multimode fiber (MMF). In this scheme, the modal dispersion and feed light crosstalk in the MMF are effectively mitigated by the combination of center-launching and offset-launching techniques. The center-launching technique is used for propagating the feed light into lower-order modes in the MMF, while the offset-launching technique is used not only for propagating the optical data signals into higher-order modes in the MMF, but also for mitigating the modal dispersion. We have successfully achieved the significant improvement in the RoF transmission performance with the 10-W feed PWoF and extended the link length up to 4 km owing to the two techniques.

Passive-demodulation pulse interferometry for ultrasound detection with high dynamic range

Yoav Hazan and Amir Rosenthal

Doc ID: 306563 Received 18 Sep 2017; Accepted 24 Jan 2018; Posted 24 Jan 2018  View: PDF

Abstract: One of the limitations associated with optical detectors of ultrasound, in particular those based on optical resonators, is their limited dynamic range. As a result, high sensitivity to weak ultrasound signals is often achieved at the price of high susceptibility to external perturbations applied on the sensing element. In this Letter, a passive demodulation scheme for pulse interferometry was developed for high dynamic-range measurements. The passive scheme was based on an unbalanced Mach-Zehnder interferometer and a 90° optical hybrid, which was implemented in a dual-polarization all-fiber setup. We demonstrated the passive scheme for detecting ultrasound bursts with pressure levels for which the response of conventional, active interferometric techniques became nonlinear.

Photonics-based coherent wideband linear frequency modulation pulsed signal generation

Yitian Tong, Daming Han, Ran Cheng, zhangweiyi Liu, Weilin Xie, Jie Qin, and Yi Dong

Doc ID: 313165 Received 23 Nov 2017; Accepted 24 Jan 2018; Posted 24 Jan 2018  View: PDF

Abstract: A photonics-based scheme is proposed to generate linear frequency modulation pulses for coherent radars with the wide bandwidths and broadly tunable carrier frequencies. The approach integrates the concept of the microwave- photonic multiplication and coherent beating to enable reconfiguration of the bandwidth and carrier frequency of the generated pulses. The phase fluctuation between two beating arms is suppressed by a stabilization technique based on the optical phase-locked loop to maintain the pulse-to-pulse phase coherence. On the basis of this scheme, we also demonstrate a coherent pulse radar system including the wireless transmission and the detection of the radar echo signal in the Ka-band. The coherent integration of several echo signals is achieved. About 8 dB signal-to-noise ratio improvement is obtained with every tenfold of integration times. The range resolution of the radar system is ~3.75 cm, which is close to the theoretical prediction.

All-fiber high-efficiency CW Raman GRIN fiber-laser pumped by a fiber-laser

Yaakov Glick, Yariv Shamir, Alexey Wolf, Alexander Dostovalov, Sergey Babin, and Shaul Pearl

Doc ID: 314530 Received 29 Nov 2017; Accepted 24 Jan 2018; Posted 24 Jan 2018  View: PDF

Abstract: We report for the first time, an all-fiber Raman graded-index (GRIN) fiber-laser pumped with a fiber-laser. This configuration points to potential future power and brightness increases. 135 Watts of CW power with an M2 value of 2.5 were obtained at a wavelength of 1081 nm with an optical to optical efficiency of 68%. A commercial GRIN core fiber acts as the Raman fiber in a power oscillator configuration which includes FBGs written onto the GRIN fiber. The efficiency and brightness demonstrated here are to the best of our knowledge the highest reported in any Raman GRIN fiber laser. A brightness enhancement of the pump beam by a factor of 5.6 is attained due to the transverse profiles of Raman gain and FBG reflection in the GRIN fiber.

Absolute sensitivity of phase measurement in an SU(1,1) type interferometer

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

Doc ID: 317971 Received 18 Dec 2017; Accepted 24 Jan 2018; Posted 24 Jan 2018  View: PDF

Abstract: Absolute sensitivity is measured for the phase measurement in an SU(1,1) type interferometer and the results are compared to that of a Mach-Zehnder interferometer operated under the condition of the same intra-interferometer intensity. The interferometer is phase locked to a point with the largest quantum noise cancellation, and a simulated phase modulation is added in one arm of SU(1,1) interferometer. Both the signal and noise level are estimated at the same frequency range, and we obtain 3 dB improvement in sensitivity for the SU(1,1) interferometer over the Mach-Zehnder interferometer. Our results demonstrate a direct phase estimation, and may pave the way for practical applications of nonlinear interferometer.

Ring-Airy beams at the wavelength limit

MARIA MANOUSIDAKI, Vladimir Fedorov, Dimitris Papazoglou, Maria Farsari, and Stelios Tzortzakis

Doc ID: 318771 Received 03 Jan 2018; Accepted 24 Jan 2018; Posted 29 Jan 2018  View: PDF

Abstract: We demonstrate that paraxial ring-Airy beams can approach the wavelength limit, while observing, a counterintuitive, strong enhancement of their focal peak intensity. Using numerical simulations, we show that this behavior is a result of the coherent constructive action of paraxial and non-paraxial energy flow. A simple theoretical model enables us to predict the parameters range over which this is possible.

Multichannel photonic Hilbert transformers based on complex modulated integrated Bragg gratings

Rui Cheng and Lukas Chrostowski

Doc ID: 314892 Received 06 Dec 2017; Accepted 23 Jan 2018; Posted 23 Jan 2018  View: PDF

Abstract: Multichannel photonic Hilbert transformers (MPHTs) are reported. The devices are based on single compact spiral integrated Bragg gratings on silicon with coupling coefficient precisely modulated by the phase of each grating period. MPHTs with up to 9 wavelength channels and a single channel bandwidth of up to ~625 GHz are achieved. The potential of the devices for multichannel single-side band signal generation is suggested. The work offers a new possibility of utilizing wavelength as an extra degree of freedom in designing RF photonic signal processors. Such multichannel processors are expected to possess improved capacities and a potential to greatly benefit current widespread wavelength division multiplexed systems.

Standoff analysis of laser-produced plasmas using laser-induced fluorescence

Sivanandan Harilal, Mark Phillips, and Brian Brumfield

Doc ID: 314399 Received 29 Nov 2017; Accepted 22 Jan 2018; Posted 25 Jan 2018  View: PDF

Abstract: We report the use of laser-induced fluorescence (LIF) of laser ablation plumes for standoff applications. The standoff analysis of Al species, as major and minor species in samples, is performed in a nanosecond laser-produced plasma created at a distance ~10 m. The LIF analysis is carried out by resonantly exciting an Al transition at 394.4 nm (2S1/2-2P1/2) using a continuous wave (cw) tunable laser and by collecting the direct-line fluorescence signal at 396.15 nm. The spectral resolution of LIF is obtained by scanning the cw tunable LIF laser across the selected Al transition. Our results highlight that LIF provides enhanced signal intensity, emission persistence, and spectral resolution when compared to thermally-excited emission, and these are crucial considerations for using laser-produced plasma for standoff isotopic analysis.

Experimental characterization of nonlinear interference noise as a process of inter-symbol interference

Ori Golani, Daniel Elson, Domanic Lavery, Lidia Galdino, Robert Killey, Polina Bayvel, and Mark Shtaif

Doc ID: 317942 Received 18 Dec 2017; Accepted 21 Jan 2018; Posted 31 Jan 2018  View: PDF

Abstract: We demonstrate a method for experimentally characterizing the second order statistics of nonlinear interference noise (NLIN) as an inter-symbol interference (ISI) process. The method enables to measure the properties of high-order ISI coefficients, which have been largely overlooked in the pass. The ability of measuring these statistics is imperative for designing effective NLIN mitigation schemes. The variance, temporal correlation times, and cross correlations of the various ISI coefficients are evaluated in several system implementations.

Athermal N-Rich Silicon Nitride Angled-MMI for coarsewavelength division (de)multiplexing in the O-band

Thalía Domínguez Bucio, Ali Khokhar, Goran Mashanovich, and Frederic Gardes

Doc ID: 314470 Received 29 Nov 2017; Accepted 20 Jan 2018; Posted 22 Jan 2018  View: PDF

Abstract: We report the design and fabrication of a compact angledmultimode interferometer (AMMI) on a 600nmthick N-rich silicon nitride platform (n=1.92) optimisedto match the ITU coarse wavelength division(de)multiplexing (CWDM) standard in the O telecommunicationband. The demonstrated device exhibited agood spectral response with Dl=20nm, BW3dB 11nm,IL<1.5dB and XT of 20dB. Additionally, it showed a hightolerance to dimensional errors <120pm/nm and lowsensitivity to temperature variations <20pm/ºC, respectively.This device had a fooprint of 0.5x2.0mm^2 withthe advantage of a simple design and a back-end-oflinecompatible fabrication process that enables multilayerintegration schemes due to its processing temperature<400ºC.

24 - 26 GHz radio over fiber and free space optics for 5G systems

Jan Bohata, Matej Komanec, Jan Spáčil, Zabih Ghassemlooy, Stanislav Zvanovec, and Radan Slavik

Doc ID: 314050 Received 21 Nov 2017; Accepted 18 Jan 2018; Posted 24 Jan 2018  View: PDF

Abstract: This paper outlines radio over fiber (RoF) combined with radio over free space optics (RoFSO) and radio frequency (RF) free-space transmission, which is of particular relevance for 5G networks. Here, the frequency band of 24 – 26 GHz is adopted to deliver high data rates and demonstrate a low-cost, compact, and high energy-efficient solution based on the direct intensity modulation and direct detection (DM-DD) scheme. For our proof-of-concept demonstration, we use 64 quadrature amplitude modulation (QAM) with a 100 MHz bandwidth and a sub-carrier within 24-26 GHz. We assess the link performance by exposing the RoFSO section to atmospheric turbulence conditions. Further, we show that the measured minimum error vector magnitude (EVM) is 4.7 % and also verify that the proposed system with the free space optics (FSO) link span of 100 m under strong turbulence can deliver an acceptable EVM of < 9% with signal-to-noise ratio (SNR) levels of 22 dB and 10 dB with and without turbulence, respectively.

Growth and lasers properties of Nd3+ doped Bi4Ge3O12 fiber single crystals

Yunkun Lin, Qinghui Wu, shaozhao wang, anhua wu, Liangbi Su, Junfeng Chen, Zhipeng Qin, Guoqiang Xie, Xiaodong Xu, Qiuhong Yang, Qingsong Song, and Lihe Zheng

Doc ID: 318662 Received 28 Dec 2017; Accepted 17 Jan 2018; Posted 12 Feb 2018  View: PDF

Abstract: The Nd3+ doped Bi4Ge3O12 ( BGO ) fiber single crystals were successfully grown by the micro-pulling-down method with the resistance heating system. The fluorescence spectra of these Nd:BGO fiber single crystals were measured ,and pumped by CW laser diode ( LD ) at maximum of 15.25 W. We observed a significant emission band peaking around 1064 and 1364 nm under 808 nm laser diodes ( LDs ) excitation, and under the condition of maximum absorption power 15.25 W , the output power of 3.37 W was obtained. The slope efficiency of 31.2% was demonstrated.

Compact and efficient mid-IR OPO source pumped by a passively Q-switched Tm:YAP laser

Brian Cole, Lew Goldberg, Stephen Chinn, L. A. Pomeranz, Kevin Zawilski, Peter Schunemann, and John McCarthy

Doc ID: 318377 Received 28 Dec 2017; Accepted 16 Jan 2018; Posted 26 Jan 2018  View: PDF

Abstract: We describe a compact and efficient mid-IR sourcebased on ZGP and CSP OPOs, operating in near degeneratecondition, directly pumped by a 1.94 μm thulium dopedyttria-aluminum-oxide (YALO, YAP) laser. TheTm:YAP laser is passively Q-switched by a chromium dopedzinc sulfide saturable absorber, and is operatedto 4Waverage power with a peak power of 29 kW. Thelaser emission was used to pump CSP and ZGP doublyresonant linear OPO cavities, generating a maximum3.5-4.2 μm mid-IR emission of 2.5 W for CSP and 2.3 Wfor ZGP, with maximum optical conversion efficienciesof 65% and 58% achieved for the two OPO crystals,respectively.

Radical passive-bleaching of Tm-doped silica fiber with deuterium

Ying-bin Xing, Ricardo Liu, Nan Zhao, Rui-ting Cao, Wang Yibo, Yu Yang, Jinggang Peng, Li qing, Luyun Yang, Nengli Dai, and Li yan

Doc ID: 315164 Received 07 Dec 2017; Accepted 13 Jan 2018; Posted 25 Jan 2018  View: PDF

Abstract: We demonstrate the almost complete 2µm-laser power recovery of the gamma-ray irradiated Tm-doped silica fiber under deuterium-loading. The optical-optical slope efficiency and the cladding absorption spectra of the Tm-doped fiber with gamma-ray irradiation and deuterium treatment have been measured for comparison. It is found that the slope efficiency of the irradiated Tm-doped fiber could be recovered to 96.1% of the pristine after deuterium bleaching, which significantly degraded from 60.7% to 25.3% after irradiation. Meanwhile, the additional absorption attenuation of the irradiated Tm-doped with D2 treatment was completely vanished. Based on the comprehensive comparison of cladding absorption spectra, the probable mechanism of the deuterium bleaching effect on irradiated Tm-doped fiber have also been discussed.

Extending the field of view by a scattering window

Mani Rai, Vijayakumar Anand, and Joseph Rosen

Doc ID: 313283 Received 10 Nov 2017; Accepted 10 Jan 2018; Posted 24 Jan 2018  View: PDF

Abstract: Interferenceless coded aperture correlation holography (I-COACH) is an incoherent digital holography technique, developed to record and reconstruct 3D images of objects without two wave interference. Herein, we introduce a novel technique to extend the field of view (FOV) of I-COACH beyond the limit imposed by the ratio between the finite area of the image sensor and the magnification of the optical system. Light diffracted from a point object located on the optical axis is modulated by a pseudorandom coded phase mask (CPM) and the central part of the point spread hologram (PSH) on the image sensor is recorded. The point object is shifted laterally to predetermined lateral locations in order to collect the exterior parts of the PSH. The recorded PSHs are stitched together to produce a synthetic PSH with an area nine times that of any individual PSH recorded by the image sensor. An object with a lateral extent beyond the FOV limit of the image sensor is placed at the same axial location as the point object and the object hologram is recorded. The object is reconstructed by a cross-correlation between the zero-padded object hologram and the synthetic PSH. Hence, the object parts beyond the FOV limit of the image sensor are recovered. A synthetic PSH library is created for different axial planes and the corresponding axial planes of the object are reconstructed.

Ultrafast mid-infrared spectrochronography of dispersion near molecular absorption bands

Aleksandr Voronin, Alexandr Lanin, Andrey Fedotov, and Aleksei Zheltikov

Doc ID: 313929 Received 20 Nov 2017; Accepted 22 Dec 2017; Posted 31 Jan 2018  View: PDF

Abstract: Quantitative characterization of dispersion near molecular resonances is difficult both conceptually and technically, as it requires systematic measurements of rapidly varying dispersion profiles across the edges of molecular absorption bands. Here, we show that this challenge can be confronted with an ultrafast spectrochronography technique that combines time-resolved four-wave mixing and cross-correlation frequency-resolved optical gating. We demonstrate that, with the spectrum of an ultrashort mid-infrared laser probe stretching over across the edge of a molecular absorption band, the Wigner chronocyclic maps of such a probe reveal universal signatures of anomalous dispersion and help quantify such dispersion anomalies.

Coherent frequency division with a degenerate synchronously pumped optical parametric oscillator

Chenchen Wan, Peng Li, Axel Ruehl, and Ingmar Hartl

Doc ID: 292655 Received 01 Sep 2017; Accepted 07 Dec 2017; Posted 23 Jan 2018  View: PDF

Abstract: Synchronously-pumped optical parametric oscillators are an important tool for frequency comb (FC) generation in the important mid-IR spectral range, where few suitable laser gain materials exist. For degenerate operation self-phase-locking to the pump FC has been demonstrated. Here, we present a phase noise study of the carrier envelope offset frequency revealing a -6 dB reduction compared to the pump frequency comb over a wide Fourier frequency range. These results demonstrate that a degenerate optical parametric oscillator can be an ideal coherent frequency divider without any excess noise.

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