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Early Posting

Accepted papers to appear in an upcoming issue

OSA now posts prepublication articles as soon as they are accepted and cleared for production. See the FAQ for additional information.

Complete snapshot Stokes polarimeter based on a single biaxial crystal

Irene Estévez, Víctor Sopo, Angel Lizana, Alex Turpin, and Juan Campos

Doc ID: 267274 Received 27 May 2016; Accepted 28 Jul 2016; Posted 28 Jul 2016  View: PDF

Abstract: We propose a new snapshot complete Stokes polarimeter based on a single biaxial crystal. The proposed optical scheme presents different strengths (snapshot, complete polarimetric measurements, large data redundancy and high sensitivity) in a simple and compact optical arrangement. The polarimeter is experimentally implemented and analyzed in terms of accuracy and repeatability.

A 4×4 InP monolithically integrated all-optical wavelength router

Xiu Zheng, Oded Raz, Nicola Calabretta, Dan Zhao, rongguo Lu, and Yong Liu

Doc ID: 268524 Received 17 Jun 2016; Accepted 27 Jul 2016; Posted 28 Jul 2016  View: PDF

Abstract: An indium phosphide based monolithically integrated wavelength router is demonstrated in this letter. The wavelength router has four inputs and four outputs, and has integrated four wavelength converters based on cross-gain modulation and cross-phase modulation effects in semiconductor optical amplifiers and a 4 × 4 arrayed-waveguide grating router. Error-free wavelength switching for a non-return-to-zero 1-1 pseudorandom binary sequence at 40 Gb/s data rate is performed. 1 × 4 and 3 × 1 all-optical routing functions of this chip are demonstrated for the first time with power penalties as low as 3.2 dB.

All-fiber pre- and post- data exchange in km-scale fiber-based twisted lights multiplexing

Jun Liu, Long Zhu, Andong Wang, Shuhui Li, Shi Chen, Cheng Du, Qi Mo, and Jian Wang

Doc ID: 268852 Received 20 Jun 2016; Accepted 27 Jul 2016; Posted 28 Jul 2016  View: PDF

Abstract: Twisting light with orbital angular momentum (OAM) provides an alternative way to facilitate space-division multiplexing (SDM). Both twisted lights (OAM modes) multiplexing transmission and data processing functions would be highly desired in a robust OAM assisted SDM (OAM-SDM) network. In this paper, we propose and demonstrate flexible all-fiber pre- and post- data exchange functions in a fiber-based OAM-SDM network. OAM+1 and OAM-1 modes carrying 5-Gbit/s 4-level pulse amplitude modulation (PAM-4) signals are multiplexed to transmit through a 1.1-km OAM fiber in the system. Two simple and controllable data exchange control units (DECUs) are placed at the front end and the back end of the OAM fiber to demonstrate pre- and post- data exchange functions between OAM+1 and OAM-1 modes. The measured optical signal-to-noise ratio (OSNR) penalties at a bit-error rate (BER) of 2×10-3 (enhanced forward-error correction (EFEC) threshold) for pre- and post- data exchange operations are less than 3.2 dB with crosstalk. The OAM data exchange functions could potentially enhance the flexibility of data management at network nodes in OAM-SDM networks.

Light guiding above the light line in arrays of dielectric nanospheres

Dmittrii Maksimov and Evgeny Bulgakov

Doc ID: 265006 Received 12 May 2016; Accepted 27 Jul 2016; Posted 28 Jul 2016  View: PDF

Abstract: We consider light propagation above the light line in arrays of spherical dielectric nanoparticles. Itis demonstrated numerically that quasi-bound leaky modes of the array can propagate both stationary wavesand light pulses to a distance of hundreds wavelengths at the frequencies close to the bound states in the radiation continuum.A semi-analytical estimate for decay rates of the guided waves is found to match the numerical data to a good accuracy.

Binary Particle Swarm Optimized 2 × 2 Power Splitters in a Standard Foundry Silicon Photonic Platform

Jason Mak, Constantine Sideris, Junho Jeong, Ali Hajimiri, and Joyce Poon

Doc ID: 269813 Received 04 Jul 2016; Accepted 26 Jul 2016; Posted 28 Jul 2016  View: PDF

Abstract: Compact power splitters designed ab initio using binary particle swarm optimization in a two dimensional mesh for a standard foundry silicon photonic platform are studied. Designs with a 4.8 mm × 4.8 mm footprintcomposed of 200 nm × 200 nm and 100 nm × 100 nm cells are demonstrated. Despite not respecting design rules, the design with the smaller cells had lower insertion losses and broader bandwidth and showed consistent behaviour across the wafer. Deviations between design and experiment point to the need for further investigations of the minimum feature dimensions.

Efficient 2122 nm Ho:YAG laser intra-cavity pumped by a narrowband-diode-pumped Tm:YAG laser

Wenxiong Lin, Haizhou Huang, Huang Jianhong, huagang liu, jinhui li, shutao dai, and wen weng

Doc ID: 264576 Received 23 May 2016; Accepted 26 Jul 2016; Posted 28 Jul 2016  View: PDF

Abstract: We first demonstrate an efficient Ho:YAG laser intra-cavity pumped by a narrowband-diode-pumped Tm:YAG laser. The pump wavelength of laser diode was selected according to the excitation peak which also the absorption peak of a 3.5 at.% Tm:YAG crystal and locked by volume Bragg gratings. In the Tm laser experiment, maximum output power of 11.12 W, corresponding to a slope efficiency of 51.6% was obtained. In the Ho laser experiment, maximum output power of 8.03 W at 2122 nm with a slope efficiency of 38% was obtained for 24.96 W of diode pump power incident onto the Tm:YAG rod.

Filtering for Unwrapping Noisy Doppler Optical Coherence Tomography Images for Extended Microscopic Fluid Velocity Measurement Range

Yang XU, Donald Darga, Jason Smid, Adam Zysk, Daniel Teh, Stephen Boppart, and P. Scott Carney

Doc ID: 268290 Received 13 Jun 2016; Accepted 26 Jul 2016; Posted 27 Jul 2016  View: PDF

Abstract: In this letter, we report the first application of two phase denoising algorithms to Doppler optical coherence tomography (DOCT) velocity maps. When combined with unwrapping algorithms, significantly extended fluid velocity dynamic range is achieved. We show cross-validations between physical simulations and the experimental results of both algorithms. We demonstrate unwrapped DOCT velocity maps having a peak velocity nearly 10 times the theoretical measurement range.

Photo-generated metasurfaces for resonant and high modulation of terahertz signals

Rafik SMAALI, Thierry Taliercio, and E. Centeno

Doc ID: 268875 Received 24 Jun 2016; Accepted 25 Jul 2016; Posted 27 Jul 2016  View: PDF

Abstract: We theoretically demonstrate a resonant modulation of THz waves with photo-designed metasurfaces. Our approach bypasses the issue of the short penetration length of the optical pump which prevents to photo-generate thick metamaterials. We propose a three layers semiconductor system of subwavelength thickness that presents a 100% modulation of the reflection (or absorption) spectra around 1 THz when it is optically actuated. This resonant modulation can be dynamically monitored at high frequency rate by the optical pump on broad range of frequencies of Δν / ν=100%. Finally, appropriate 2D photo-printed patterns make the system polarization insensitive and operational for a wide range of incident angles up to 65°.

Application of the speckle-based phase retrieval method in reconstructing two unknown interfering wavefronts

Roghayeh Yazdani and Hamid Fallah

Doc ID: 269001 Received 22 Jun 2016; Accepted 25 Jul 2016; Posted 28 Jul 2016  View: PDF

Abstract: We numerically demonstrate a novel method to simultaneously reconstruct two unknown interfering wavefronts. The speckle-based phase retrieval technique isapplied to derive the interference field. The derived interference field along with the phase shifting concept is used for calculating the interfering wavefronts. Our results show the success of this method even under noisyconditions.

Generation of stretched pulses and dissipative solitons at 2 μm from an all-fiber mode-locked laser using carbon nanotube saturable absorbers

Yu Wang, Shaif-Ul Alam, Elena Obraztsova, Sze Set, Shinji Yamashita, and Anatoly Pozharov

Doc ID: 263524 Received 22 Apr 2016; Accepted 25 Jul 2016; Posted 25 Jul 2016  View: PDF

Abstract: We demonstrate, for the first time to the best of our knowledge, a Thulium-doped all-fiber mode-locked laser using a carbon nanotube saturable absorber, operating in the dissipative-soliton regime and the stretched-pulse-soliton regime. The net dispersion of the laser cavity is adjusted by inserting different lengths of normal dispersion fiber, resulting in different mode-locking regimes. These results could serve as a foundation for the optimization of mode-locked fiber laser cavity design at the 2 μm wavelength region.

Guiding and nonlinear coupling of light in plasmonic nanosuspensions

Yuxuan Ren, Trevor Kelly, Akbar Samadi, Anna Bezryadina, Demetrios Christodoulides, and Zhigang Chen

Doc ID: 266537 Received 24 May 2016; Accepted 24 Jul 2016; Posted 25 Jul 2016  View: PDF

Abstract: We demonstrate two different types of coupled beam propagation dynamics in colloidal gold nanosuspensions. In the first case, an infrared probe beam (1064nm) is guided by a low-power visible beam (532nm) in gold nanosphere or nanorod suspensions due to the formation of a plasmonic resonant soliton. Although the infrared beam itself does not experience nonlinear self-action effects even at high power levels, needle-like deep penetration of both beams through otherwise highly dissipative suspensions is realized. In the second case, a master/slave-type nonlinear coupling is observed in gold nanoshell suspensions, in which the nanoparticles have opposite polarizabilities at the visible and infrared wavelengths. In this latter regime, both beams experience a self-focusing nonlinearity that can be fine-tuned.

Adaptive Optics Parallel Confocal Scanning Ophthalmoscopy

Yuhua Zhang, Jing Lu, Boyu Gu, and Xiaolin Wang

Doc ID: 268227 Received 13 Jun 2016; Accepted 21 Jul 2016; Posted 21 Jul 2016  View: PDF

Abstract: We present an adaptive optics parallel confocal scanning ophthalmoscope (AOPCSO) using a digital micromirror device (DMD). The imaging light is shaped into a line of point sources by the DMD, forming parallel illumination on the retina. By using a high speed line camera to acquire image and using adaptive optics to compensate ocular wave aberration, the AOPCSO can image the living human eye with cellular level resolution at the frame rate of 100 Hz. High speed AOPCSO has been demonstrated with improved spatial resolution in imaging of the living human and has the potential to further improve image fidelity.

Demonstration of ultra-broadband single-mode and single-polarization operation in T-Guides

Sasan Fathpour and Jeff Chiles

Doc ID: 269000 Received 24 Jun 2016; Accepted 21 Jul 2016; Posted 25 Jul 2016  View: PDF

Abstract: Silica-based anchored-membrane waveguides (T-Guides) are fabricated and characterized from the visible to infrared with streak imaging. It is numerically shown that the T-Guides can have wideband single-mode and single-polarization (SMSP) properties over a span of 2.6 octaves. Experimentally, a polarization-dependent loss difference of up to 90 dB/cm is measured between orthogonal polarizations, and a record SMSP window of > 1.27 octaves is observed, limited only by the available measurement equipment. These measurements make a strong case for T-Guides for SMSP photonics, particularly on high-index materials such as our previous demonstration on silicon.

Dispersion of nonlinear refractive index in layered WS2 and WSe2 semiconductor films induced by two photon absorption

Jun Wang, Ningning Dong, Yuanxin Li, Saifeng Zhang, Niall McEvoy, Xiaoyan Zhang, cui yun, Long Zhang, and Georg Duesberg

Doc ID: 268001 Received 09 Jun 2016; Accepted 20 Jul 2016; Posted 21 Jul 2016  View: PDF

Abstract: Both the nonlinear absorption and nonlinear refraction properties of WS2 and WSe2 semiconductor films have been characterized by using Z-scan technique with fs pulses at the wavelength of 1040 nm. It is found that these films have two photon absorption response with the nonlinear absorption coefficient of ~103 cm GW-1, and a dispersion of nonlinear refractive index in the WS2 films that translated from positive in the monolayer to negative in bulk materials. © 2016 Optical Society of America

Measurement of complex refractive index of turbid media by scanning focused refractive index

Qing Ye, Tengqian Sun, Shike Liu, Xiaowan Wang, Jin Wang, Zhichao Deng, Jianchun Mei, Wen-Yuan Zhou, Jian-Guo Tian, and Chunping Zhang

Doc ID: 257401 Received 14 Jan 2016; Accepted 20 Jul 2016; Posted 21 Jul 2016  View: PDF

Abstract: We present the application of scanning focused refractive index microscopy (SFRIM) in the complex refractive index (CRI) measurement of turbid media. An extra standard scattering layer is placed in front of the detector to perform scattering transformation on the reflected light. The principle of the scattering transformation is elaborated theoretically. The influence of the sample scattering is deeply and effectively suppressed experimentally. As a proof of the feasibility and accuracy of the proposed method, we demonstrate experimental data of 20% and 30% Intralipid solutions that are commonly used as phantom medium for light propagation studies.

Crosstalk analysis in multicore optical fibers by supermode theory

Lukasz Szostkiewicz, Marek Napierała, Anna Ziołowicz, Anna Pytel, Tadeusz Tenderenda, and Tomasz Nasilowski

Doc ID: 262939 Received 12 Apr 2016; Accepted 20 Jul 2016; Posted 20 Jul 2016  View: PDF

Abstract: We discuss the theoretical aspects of core to core power transfer in multicore fibers relying on supermode theory. Based on a dual core fiber model, we investigate the consequences of this approach, such as the influence of initial excitation conditions on crosstalk. Supermode interpretation of power coupling proves to be intuitive and thus may lead to new concepts of multicore fiber based devices. As a conclusion we propose a definition of uniform crosstalk parameter that describes multicore fiber design

Optical vector analysis based on double-sideband modulation and stimulated Brillouin scattering

Shilong Pan, Ting Qing, Li Shupeng, and Min Xue

Doc ID: 264369 Received 02 May 2016; Accepted 20 Jul 2016; Posted 20 Jul 2016  View: PDF

Abstract: A high-resolution and high-accuracy optical vector analysis (OVA) based on optical double-sideband (ODSB) modulation and stimulated Brillouin scattering (SBS) is proposed and experimentally demonstrated. Different from the conventional OVA based on optical single-sideband (OSSB) modulation, in which the measurement range is limited by the bandwidth of microwave and optoelectronic components and the measurement accuracy is restricted by the high-order sidebands, the proposed technique measures the magnitude and phase responses by taking use of both ±1st-order sidebands without spectrum response aliasing. As a result, the measurement range is doubled and the measurement errors produced by high-order sidebands is eliminated. A proof-of-concept experiment is carried out. The transmission response of a fiber Bragg grating (FBG), in a range of 80 GHz, is measured with a resolution of less than 667 kHz by using 40-GHz microwave components.

Thin Absorber Extreme Ultraviolet Photomask Based on Ni--TaN Nanocomposite Material

Zhimin Shi, Darrick Hay, PATRICK Bagge, Ian Khaw, Lei Sun, Obert Wood, Yulu Chen, RYOUNG-HAN Kim, and ZHENGQING Qi

Doc ID: 266689 Received 20 May 2016; Accepted 20 Jul 2016; Posted 20 Jul 2016  View: PDF

Abstract: We study the use of random nano-composite material as a photomask absorber layer for the next generation of extreme ultraviolet (EUV) lithography. By introducing nickle nano-particles (NPs) randomly into a TaN host, the nanocomposite absorber layer can greatly reduce the reflectivity as compared to the standard TaN layer of the same thickness. Finite integral simulations show that the reduction in the reflectivity is mainly due to the enhanced absorption by the Ni NPs. The fluctuation in reflectivity induced by scattering and random position of the NPs are found to be on the order of 0.1\%. Based on these observations, we build an effective medium model for the nanocomposite absorber layer, and use transfer matrix method to identify optimal absorber designs that utilize some cavity effect to reduce the required volume fraction of Ni NPs. We further perform a process simulation and show that our approach can greatly reduce the HV bias in the lithography process.

Broadband electric-field-induced LP₀₁ and LP₀₂ second harmonic generation in Xe-filled hollow-core PCF

Jean-Michel Menard, Felix Köttig, and Philip Russell

Doc ID: 266915 Received 24 May 2016; Accepted 20 Jul 2016; Posted 20 Jul 2016  View: PDF

Abstract: Second harmonic (SH) generation with 300 fs pump pulses is reported in a xenon-filled hollow-core photonic crystal fiber (PCF) across which an external bias voltage is applied. Phase-matched intra-modal conversion from pump light in the LP₀₁ mode to SH light in the LP₀₂ mode is achieved at a particular gas pressure. Using periodic electrodes, quasi-phase-matched SH generation directly into the low-loss LP₀₁ mode is achieved at a different pressure. The low linear dispersion of the gas enables phase-matching over a broad spectral window, resulting in a measured bandwidth of ~10 nm at high pump energies. A conversion efficiency of ~18 %/mJ is obtained. Gas-filled anti-resonant-reflecting hollow-core PCF uniquely offers pressure-tunable phase-matching, ultra-broadband guidance and a very high optical damage threshold, which hold great promise for efficient three-wave mixing, especially in difficult-to-access regions of the electromagnetic spectrum.

Satellite laser ranging using superconducting nanowire single-photon detectors at 1064 nm wavelength

Ming Li, Li Xue, Zhulian Li, Labao Zhang, zhai dongsheng, Yuqiang Li, Sen Zhang, Lin Kang, Jian Chen, Peiheng Wu, and Yaoheng Xiong

Doc ID: 264541 Received 04 May 2016; Accepted 19 Jul 2016; Posted 20 Jul 2016  View: PDF

Abstract: Satellite laser ranging operating at 1064 nm wavelength using superconducting nanowire single-photon detectors (SSPDs) is successfully demonstrated. The SSPD with a quantum efficiency (QE) of 80% and a dark count rate (DCR) of 100 cps at 1064 nm wavelength is developed and introduced to Yunnan Observatory. With improved closed-loop systems (field of view of about 26”), satellites including Cryosat, Ajisai, and Glonass with ranges of 1,600km, 3,100km, and 19,500km are experimentally ranged with mean echo rate of 1,200/min, 4,200/min, and 320/min, respectively. To the best of our knowledge, this is the first demonstration of laser ranging for satellites using SSPDs at 1064 nm wavelength. Theoretical analysis of the detection efficiency and the mean echo rate for typical satellites indicates that it is possible for SSPD to range satellites from low earth orbit (LEO) to geostationary earth orbit (GEO).

Quantum-Dot Saturable Absorber and Kerr-Lens Mode-Locked Yb:KGW Laser with >450 kW of Peak Power

Reza Akbari, Arkady Major, haitao zhao, Edik Rafailov, and Ksenia Fedorova

Doc ID: 264023 Received 02 May 2016; Accepted 19 Jul 2016; Posted 21 Jul 2016  View: PDF

Abstract: Hybrid action of quantum-dot saturable absorber and Kerr-lens mode-locking in a diode-pumped Yb:KGW laser was demonstrated. Using a quantum-dot saturable absorber with 0.7% (0.5%) modulation depth, the mode-locked laser delivered 90 fs (93 fs) pulses with 3.2 W (2.9 W) of average power at the repetition rate of 77 MHz, corresponding to 462 kW (406 kW) of peak power and 41 nJ (38 nJ) of pulse energy. To the best of our knowledge, this represents the highest average and peak powers generated to date from a quantum-dot saturable absorber based mode-locked lasers.

Detection of a diffusive cloak via second-order statistics

Milan Koirala and Alexey Yamilov

Doc ID: 268045 Received 09 Jun 2016; Accepted 19 Jul 2016; Posted 21 Jul 2016  View: PDF

Abstract: We propose a scheme to detect the diffusive cloak proposed by Schittny et al [Science 345, 427 (2014)]. We exploit the fact that diffusion of light is an approximation that disregards wave interference. The long-range contribution to intensity correlation is sensitive to locations of paths crossings and the interference inside the medium, allowing one to detect the size and position,including the depth, of the diffusive cloak. Our results also suggest that it is possible to separately manipulate the first- and the second-order statistics of wave propagation in turbid media.

Temperature-Dependent Excitonic photoluminescence Excited by Two-Photon Absorption in Perovskite CsPbBr3 Quantum Dots

Tian Jiang, Zhongjie Xu, Runze Chen, Xin Zheng, Xiang'ai Cheng, and Ke We

Doc ID: 268661 Received 11 Jul 2016; Accepted 19 Jul 2016; Posted 21 Jul 2016  View: PDF

Abstract: Recently lead halide perovskite quantum dots have been reported with potential for photovoltaic and optoelectronic applications due to their excellent luminescent properties. Herein excitonic photoluminescence (PL) excited by two-photon absorption in perovskite CsPbBr3 quantum dots (QDs) have been studied at a broad temperature range from 80K to 380K. Two-photon absorption has been investigated and the absorption coefficient is up to 0.085 cm/GW at room temperature. Moreover, the PL spectrum excited by two-photon absorption shows a linear blue-shift (0.32meV/K) below the temperature of 220K. However, for higher temperature, the PL peak approaches a roughly constant value and shows temperature-independent chromaticity up to 380K. This behavior is distinct from general red-shift for semiconductors and can be attributed to the result of thermal expansion, electron–phonon interaction and structural phase transition around 360K. The strong nonlinear absorption and temperature-independent chromaticity of CsPbBr3 QDs observed in temperature range from 220K to 380K will offer new opportunities in nonlinear photonics, light-harvesting and light-emitting devices.

Cascaded Parametric Amplification for Highly Efficient Terahertz Generation

Koustuban Ravi, Michaël Hemmer, Giovanni Cirmi, Fabian Reichert, Damian Schimpf, Oliver Muecke, and Franz Kaertner

Doc ID: 267022 Received 10 Jun 2016; Accepted 19 Jul 2016; Posted 25 Jul 2016  View: PDF

Abstract: A highly efficient, practical approach to high-energy multi-cycle terahertz (THz) generation based on spectrally cascaded optical parametric amplification (THz-COPA) is introduced. Feasible designs are presented that enable the THz wave, initially generated by difference frequency generation between a narrowband optical pump and optical seed (0.1-10% of pump energy), to self-start a cascaded (or repeated) energy down-conversion of pump photons in a single pass through a single crystal. In cryogenically cooled, periodically poled lithium niobate, unprecedented energy conversion efficiencies >8% achievable with existing pump laser technology are predicted using realistic simulations. The calculations account for cascading effects, absorption, dispersion and laser-induced damage. Due to simultaneous, coupled nonlinear evolution of multiple phase-matched triplets of waves, THz-COPA exhibits physics distinctly different from conventional three-wave mixing parametric amplifiers. This in turn governs optimal phase-matching conditions, evolution of optical spectra and limitations of the nonlinear process. Circumventing these limitations is shown to yield conversion efficiencies >> 10%.

Scattering Robust 3D Reconstruction via Polarized Transient Imaging

Jinli Suo, Rihui Wu, Feng Dai, YongDong Zhang, and Qionghai Dai

Doc ID: 259785 Received 22 Feb 2016; Accepted 18 Jul 2016; Posted 22 Jul 2016  View: PDF

Abstract: Reconstructing 3D structure of scenes behind the scattering medium is a challenging task and of great research value. Existing techniques often impose some strong assumptions on the scattering behaviors and are of limited performance. Recently, low cost transient imaging system provides a new feasible way to resolve the scene depth, by detecting the reflection instant on the time profile of a surface point. However, in the cases with scattering medium, the rays are both reflected and scattered during transmission, and the depth calculated from the time profile largely deviates from the true value. To handle this problem, we make use of the different polarization behaviors of reflection and scattering components, and introduce active polarization to separate out the reflection component for scattering robust depth estimation. Experiments demonstrate that the proposed approach can reconstruct the 3D structure underlying scattering medium at a promising accuracy.

Ultra-sensitive and super-resolving angular rotation measurement based on photon orbital angular momentum using parity measurement

Jing Zhang, Tianyuan Qiao, Kun Ma, Longzhu Cen, Jiandong Zhang, Feng Wang, and Yuan Zhao

Doc ID: 269286 Received 28 Jun 2016; Accepted 18 Jul 2016; Posted 22 Jul 2016  View: PDF

Abstract: Photon orbital angular momentum has led to many novel insights and applications in quantum measurement. Photon orbital angular momentum can increase the resolution and sensitivity of angular rotation measurement. However, quantum measurement strategy can further surpass this limit and improve the resolution of angular rotation measurement. This paper proposes and demonstrates parity measurement method in angular rotation measurement scheme for the first time. Parity measurement can make the resolution superior to the limit of existing method. The sensitivity can be improved with higher orbital angular momentum photon. Moreover, this paper gives a detailed discussion of the change of resolution and sensitivity in the presence of photon loss.

Dual-period tunable phase grating based on a single in-plane switching

Jiliang Zhu, Liang Gao, Zhe-Zhe Zheng, Wen-Ming Han, and Yubao Sun

Doc ID: 267426 Received 31 May 2016; Accepted 18 Jul 2016; Posted 20 Jul 2016  View: PDF

Abstract: We proposed a dual-period phase grating using a polymer-stabilized blue phase liquid crystal (PS-BPLC). High efficiency of 38% for the short-period phase grating and 30% for the long-period phase grating have been achieved because of the electric-field-induced rectangular-like phase profile of PS-BPLC, which agrees quit well with the simulation results. The diffraction angle and diffraction efficiency can be alternatively tuned by a bias-voltage and intensity of applied voltage. The diffracted light of each diffraction orders is elliptically polarized, and its ellipticity is larger than that induced by using the conventional nematic LCs. Such device also shows sub-millisecond response time and holds great potential for photonics applications.

Phase-dependent interference between frequency doubled comb lines in a χ(2) phase-matched AlN microring

Hojoong Jung, Xiang Guo, Na Zhu, Scott Papp, Scott Diddams, and Hong Tang

Doc ID: 267509 Received 02 Jun 2016; Accepted 18 Jul 2016; Posted 20 Jul 2016  View: PDF

Abstract: Nonlinear optical conversion with frequency combs is important for self-referencing and for generating shorter wavelength combs. Here we demonstrate efficient frequency-comb doubling through the combination of second-harmonic generation (SHG) and sum-frequency generation (SFG) of an input comb with a high Q, phase-matched χ(2) microring resonator. Phase coherence of the SHG and SFG nonlinear conversion processes is confirmed by sinusoidal phase-dependent interference between frequency doubled comb lines.

Actively phase-controlled coupling between plasmonic waveguides via in-between gain-assisted nanoresonator: Nanoscale optical logic gates

Song-Jin Im, Kum-Song Ho, Yong-Ha Han, and Chol-Song Ri

Doc ID: 267695 Received 08 Jun 2016; Accepted 18 Jul 2016; Posted 20 Jul 2016  View: PDF

Abstract: The development of nanoscale optical logic gates have attracted immense attention due to increasing demand for ultrahigh-speed and energy-efficient optical computing and data processing, however suffers from the difficulty in precise control of phase difference of the two optical signals. We propose a novel conception of nanoscale optical logic gates based on actively phase-controlled coupling between two plasmonic waveguides via in-between gain-assisted nanoresonator. Precise control of phase difference between the two plasmonic signals can be performed by manipulating pumping rate at an appropriate frequency detuning, enabling a high contrast between the output logic states "1" and "0". Without modification of the structural parameters, different logic functions can be provided. This active nanoscale optical logic device is expected to be quite energy-efficient with ideally low energy consumption on the order of 0.1 fJ/bit. Analytical calculations and numerical experiments demonstrate the validity of the proposed concept.

Demonstration of optical multicasting using Kerr frequency comb lines

Changjing Bao, Peicheng Liao, Arne Kordts, Maxim Karpov, Martin Pfeiffer, Lin Zhang, Yan Yan, Guodong Xie, Yinwen Cao, Ahmed Almaiman, Morteza Ziyadi, Long Li, Zhe Zhao, Amirhossein Mohajerin Ariaei, Steven Wilkinson, Moshe Tur, Martin Fejer, Tobias Kippenberg, and Alan Willner

Doc ID: 269270 Received 27 Jun 2016; Accepted 18 Jul 2016; Posted 27 Jul 2016  View: PDF

Abstract: We experimentally demonstrate optical multicasting using Kerr frequency combs generated from a Si3N4 microresonator. We obtain Kerr combs in two states with different noise properties by varying the pump wavelength in the resonator and investigate the effect of Kerr combs on multicasting. Seven-fold multicasting of 20-Gbaud quadrature phase-shift-keyed signals and four-fold multicasting of 16-quadrature amplitude modulation signals have been achieved when low-phase-noise combs are input into a periodically poled lithium niobate waveguide. Also, we find that the wavelength conversion efficiency in the PPLN waveguide for chaotic combs with high noise is similar to that for low-noise combs, while the signal quality of the multicast copy is significantly degraded.

Direct Regenerative Amplification of Femtosecond Pulses to the multi-mJ Level

Moritz Ueffing, Robert Lange, Tobias Pleyer, Vladimir Pervak, Thomas Metzger, Dirk Sutter, Zsuzsanna Major, Thomas Nubbemeyer, and Ferenc Krausz

Doc ID: 270594 Received 14 Jul 2016; Accepted 18 Jul 2016; Posted 20 Jul 2016  View: PDF

Abstract: We present a compact femtosecond nonlinear Yb:YAGthin-disk regenerative amplifier delivering pulses carriedat a wavelength of 1030nm with an average powerof >200W at a repetition rate of 100 kHz and an energynoise value of 0.46% (rms) in a beam with apropagation factor of M2<1.4. The amplifier is seededwith bandwidth-limited sub-picosecond pulses withouttemporal stretching. We give estimates for the nonlinearparameters influencing the system and show thatchirped mirrors compress the 2 mJ pulses to a nearbandwidth-limited duration of 210 fs.

Towards user mobility for OFDM-based visible light communications

Yang Hong and Lian-Kuan Chen

Doc ID: 265385 Received 17 May 2016; Accepted 18 Jul 2016; Posted 20 Jul 2016  View: PDF

Abstract: We propose and experimentally demonstrate a mobile visible light communications (mobi-VLC) transmission system. The impact of user mobility on the performance of the mobi-VLC system is characterized and we propose the use of the channel-independent orthogonal circulant matrix transform (OCT) precoding to combat the packet loss performance degradation induced by mobility. A mobile user terminal is used to detect the signal from a blue laser placed at 1 meter away from the moving track. Various moving speeds (20, 40, 60, and 80 cm/s) and lateral moving distances (30, 40, and 50 cm) of the user terminal are investigated. The effectiveness of the OCT precoding is evaluated by the comparison with the conventional orthogonal frequency division multiplexing (OFDM) scheme and the adaptive-loaded discrete multi-tone (DMT) scheme. Experimental results show that the system performance degrades with the increase in user mobility speed and in moving distance. Furthermore, the OCT precoding provides superior performance improvement than that of conventional OFDM schemes and it also exhibits lower packet loss rate than that of adaptive-loaded DMT. No packet loss for 300-Mb/s transmission is achieved with 30-cm lateral moving distance at 20 cm/s.

Nanofiber-segment ring resonator

Todd Pittman, Daniel Jones, Garrett Hickman, and James Franson

Doc ID: 267312 Received 01 Jun 2016; Accepted 18 Jul 2016; Posted 19 Jul 2016  View: PDF

Abstract: We describe a fiber ring resonator comprised of a relatively long loop of standard single-mode fiber with a short nanofiber segment. The evanescent mode of the nanofiber segment allows the cavity-enhanced field to interact with atoms in close proximity to the nanofiber surface. We report on an experiment using a warm atomic vapor and low-finesse cavity, and briefly discuss the potential for reaching the strong coupling regime of cavity QED by using trapped atoms and a high-finesse cavity of this kind.

Integrated plasmonic nanotweezers for nanoparticles manipulation

Giovanni Magno, Aurore Ecarnot, Christophe Pin, Vy Yam, Robert Mégy, Philippe Gogol, Benoît Cluzel, and Beatrice Dagens

Doc ID: 268718 Received 23 Jun 2016; Accepted 18 Jul 2016; Posted 19 Jul 2016  View: PDF

Abstract: We numerically demonstrate that short gold nanoparticle chains coupled to traditional SOI waveguides allow conceiving surface plasmon-based nanotweezers. This configuration provides for a jumpless control of the trapping position of a nanoobject as a function of the excitation wavelength, allowing for linear repositioning. This novel feature can be captivating for the conception of compact integrated optomechanical nanoactuators.


Jinkang Lim, abhinav vinod, Shu-Wei Huang, Andrey Matsko, Anatoliy Savchenkov, Lute Maleki, Chee Wei Wong, parastou MORTAZAVIAN, Dim-Lee Kwong, and Mingbin Yu

Doc ID: 268903 Received 24 Jun 2016; Accepted 18 Jul 2016; Posted 19 Jul 2016  View: PDF

Abstract: We stabilize a chip-scale Si3N4 phase-locked Kerr frequency comb via locking the pump laser to an independent stable high-Q reference microresonator and locking the comb spacing to an external microwave oscillator. In this comb, the pump laser shift induces negligible impact on the comb spacing change. This scheme is a step towards miniaturization of the stabilized Kerr comb system as the microresonator reference can potentially be integrated on-chip. Fractional instability of the optical harmonics of the stabilized comb is limited by the microwave oscillator used for comb spacing lock below 1 s averaging time and coincides with the pump laser drift in the long term.

Asymmetrically Contacted Germanium Photodiode using Metal–Interlayer–Semiconductor–Metal Structure for Extremely Large Dark Current Suppression

Hyun-Yong Yu, HWAN-JUN Zang, Gil-jae Park, YONG-SOO CHOI, and GWANG-SIK KIM

Doc ID: 267321 Received 09 Jun 2016; Accepted 17 Jul 2016; Posted 19 Jul 2016  View: PDF

Abstract: In this work, we propose germanium (Ge) metal–interlayer–semiconductor–metal (MISM) photodiode (PD), where the anode is metal–interlayer–semiconductor (MIS) contact, and the cathode is metal–semiconductor (MS) contact, to efficiently suppress the dark current of Ge PD. We selected titanium dioxide (TiO2) as an interlayer material for the MIS contact, due to its large valence band offset and zero conduction band offset to Ge. We significantly suppress the dark current of Ge PD by introducing the MISM structure with TiO2 interlayer, as this enhances the hole Schottky barrier height, and thus acts as a large barrier for holes. In addition, it collects photo-generated carriers without degradation, due to its zero conduction band offset to Ge. This reduces the dark current of Ge MISM PDs by ×8,000 for 7 nm-thick TiO2 interlayer, while its photo current is still comparable to that of Ge metal–semiconductor–metal (MSM) PDs. Furthermore, the proposed Ge PD shows ×6,600 improvement of the normalized photo-to-dark-current ratio (NPDR) at wavelength of 1.55 µm. The proposed Ge MISM PD shows considerable promise for low power and high sensitivity Ge-based optoelectronic applications.

Security-enhanced chaos communication with time-delay signature suppression and phase encryption

Ning Jiang, Chenpeng Xue, Yunxin Lv, Chao Wang, Shuqing Lin, Guilan Li, and Kun Qiu

Doc ID: 268496 Received 16 Jun 2016; Accepted 17 Jul 2016; Posted 19 Jul 2016  View: PDF

Abstract: A security-enhanced chaos communication scheme with time delay signature (TDS) suppression and phase-encrypted feedback light is proposed, in virtue of dual-loop feedback with independent high-speed phase modulation. We numerically investigate the property of TDS suppression in both the intensity and phase space and quantitatively discuss the security of proposed system by calculating the bit-error-rate of eavesdroppers who try to crack the system by directly filtering the detected signal or using a similar semiconductor laser to synchronize the link signal and extract the data. The results show that TDS embedded in the chaotic carrier can be well suppressed by properly setting the modulation frequency, which can keep secret the time delay to the eavesdropper. Moreover, since the feedback light is encrypted, without the accurate time delay and key, the eavesdropper cannot reconstruct the symmetric operation conditions and decode the correct data.

Experimental demonstration of a two-mode (de)multiplexer based on a taper-etched directional coupler

Yao Sun, Yule Xiong, and Winnie Ye

Doc ID: 267200 Received 30 May 2016; Accepted 17 Jul 2016; Posted 19 Jul 2016  View: PDF

Abstract: We experimentally demonstrate a compact, low crosstalk and fabrication tolerant two-mode (de)multiplexer on the silicon-on-insulator platform. The device consists of a silicon wire waveguide coupled to a taper-etched waveguide. The partially etched taper structure is used to relax fabrication tolerance and thus to ensure high mode conversion efficiency. The device is 68 μm in length, with a TE0-to-TE1 mode conversion loss of better than -0.8 dB demonstrated over the C-band wavelengths. In addition, the device demonstrates a low TE-to-TE through insertion loss of better than -1.3 dB with modal crosstalk lower than -26 dB, over a 65 nm wavelength range. Finally, we have experimentally demonstrated that the device is tolerant to fabrication errors as large as 40 nm.

Second Harmonic Generation and Waveguide Properties in perovskite Na0.5Bi0.5TiO3 Nanowires

anlian pan, Hong Zhou, XIAOXIA WANG, and Xiujuan Zhuang

Doc ID: 270277 Received 13 Jul 2016; Accepted 16 Jul 2016; Posted 20 Jul 2016  View: PDF

Abstract: Nanowires with non-linear optical properties such as second harmonic generation (SHG) are essential elements for all-optical integrated photonic circuit. However, the existing materials face challenges for applications in a wide wavelength range. To cope with the challenges, ferroelectric nanowires are considered as promising candidates especially for SHG applications. In this paper, we study SHG and waveguide properties in perovskite Na0.5Bi0.5TiO3 (NBT) nanowires. Strong SHG is observed from NBT nanowires illuminated by a 1064 nm laser radiation. For the waveguide studies, these NBT nanowires show a waveguide propagation loss as low as 0.01dB/μm at 532 nm. This work suggests potential applications in future integrated optics with NBT nanowires.

Coherent continuous-wave dual-frequency high-Q external-cavity semiconductor laser for GHz to THz applications

Stéphane Blin, Romain Paquet, Mikhaël Myara, Luc Legratiet, mohamed sellahi, Baptiste Chomet, Grégoire Beaudoin, Isabelle Sagnes, and Arnaud Garnache

Doc ID: 266980 Received 26 May 2016; Accepted 16 Jul 2016; Posted 18 Jul 2016  View: PDF

Abstract: We report a continuous-wave highly-coherent and tunable dual-frequency laser emitting at two frequencies separated by 30 GHz to 3 THz, based on a compact III- V diode-pumped quantum-well surface emitting semiconductor laser technology. The concept is based on stable simultaneous operation of two Laguerre-Gauss transverse modes in a high-Q single-axis short cavity, using an integrated sub-wavelength-thick metallic mask. Simultaneous operation is demonstrated theoretically, and experimentally by recording microwave intensity noises and beat frequency, and time-resolved optical spectra. We demonstrated > 80mW output power, diffraction limited beam, narrow linewidth < 300 kHz, linear polarization state (> 45 dB) and low intensity noise class-A dynamics < 0.3 % rms. Such high performances laser opens the path to compact low cost coherent GHz to THz source development.

Graphene-Based Terahertz Metasurface with Tunable Spectrum Splitting

Zhaoxian Su, Xuan Chen, Jianbo Yin, and X Zhao

Doc ID: 267838 Received 08 Jun 2016; Accepted 16 Jul 2016; Posted 18 Jul 2016  View: PDF

Abstract: We design a tunable terahertz metasurface, which consists of two different trapezoid graphene ribbons patterned in opposite direction and a gold film, separated by a thin dielectric spacer. The two kinds of graphene ribbon can cover nearly 2π phase region with high reflection efficiency in different spectral region so that the metasurface can reflect different frequency waves to totally different directions. By changing the Fermi level of graphene ribbons, the response frequency of the proposed metasurface can be adjusted, as a result, tunable spectrum splitting can be realized. The present metasurface provides a powerful way for controlling terahertz waves, and has an application potential for wide-angle beam splitters.

Si-prism-array coupled terahertz-wave parametric oscillator with pump light totally reflected at THz-wave exit surface

Yanchen Qu, Ruiliang Zhang, Wei Jiang Zhao, Chuang Liu, and Zhenlei Chen

Doc ID: 268486 Received 15 Jun 2016; Accepted 15 Jul 2016; Posted 18 Jul 2016  View: PDF

Abstract: A Si-prism-array coupled terahertz-wave parametric oscillator with the pump totally reflected at the THz-wave exit surface (PR-Si-TPO) is demonstrated by manufacturing an 800-nm air gap between the crystal and Si-prism array. Influence to total reflection of the pump from the Si prisms is eliminated and efficient coupling of the THz wave is ensured by using this air gap. When THz-wave frequency varies from 1.7 to 2.3 THz, compared with a Si-prism-array coupled TPO (Si-TPO) with the pump transmitting through the crystal directly, the THz-wave output energy is enhanced by 20~50 times, the oscillating threshold is reduced by 10%~35%. Furthermore, the high end of the THz-wave frequency tuning range of the PR-Si-TPO is expanded to 3.66THz compared with 2.5 THz for the Si-TPO.

Stimulated Raman Scattering microscopy by Nyquist modulation of a two-branch ultrafast fiber source

Andreas Zumbusch, Alfred Leitenstorfer, Daniele Brida, Claudius Kocher, Claudius Riek, Peyman Zirak Yousefabadi, Christoph Kölbl, and Peter Fimpel

Doc ID: 269155 Received 24 Jun 2016; Accepted 15 Jul 2016; Posted 18 Jul 2016  View: PDF

Abstract: A highly stable setup for stimulated Raman scattering (SRS) microscopy is presented. It is based on a two-branch femtosecond Er:fiber laser operating at 40 MHz repetition rate. One of the outputs is directly modulated at the Nyquist frequency with an integrated electro-optic modulator (EOM). This compact source combines jitter-free pulse synchronization with broad tunability and allows for shot-noise limited SRS detection. The performance of the SRS microscope is illustrated with measurements on samples from material science and cell biology.

Multi-Watt Continuous Wave Nd:KGW Laser With Hot Band Diode Pumping

Arkady Major, RUBEL TALUKDER, Md. Zubaer Eibna Halim, and Tanant Waritanant

Doc ID: 268828 Received 21 Jun 2016; Accepted 15 Jul 2016; Posted 21 Jul 2016  View: PDF

Abstract: We have demonstrated what we believe is the first continuous wave Nd:KGW laser with hot band diode pumping at ~910 nm. This pumping wavelength reduced the quantum defect by >46% as compared to the conventional ~810 nm pumping and resulted in significantly lower thermal lensing. The laser produced 2.9 W of average output power at 1067 nm in a diffraction limited beam for an absorbed pump power of 8.3 W. The slope efficiency and optical-to-optical efficiency were found to be 43% and 35%, respectively. Significant reduction of quantum defect offered by this pumping wavelength and availability of suitable high power laser diodes opens an attractive way to further power and efficiency scaling of the Nd:KGW lasers.

High resolution confocal Raman microscopy using pixel-reassignment

Clemens Roider, Alexander Jesacher, and Monika Ritsch-Marte

Doc ID: 269783 Received 05 Jul 2016; Accepted 15 Jul 2016; Posted 25 Jul 2016  View: PDF

Abstract: We present a practical modification of fibre coupled confocal Raman scanning microscopes that is able to provide high confocal resolution in conjunction with high light collection efficiency. For this purpose, the single detection fibre is replaced by a hexagonal lenslet array in combination with a hexagonally packed round-to-linear multimode fibre bundle. A multiline detector is used to collect individual Raman spectra for each fibre. Data post processing based on pixel-reassignment allows one to improve the lateral resolution by up to 41% compared to a single fibre of equal light collection efficiency. We present results from an experimental implementation featuring seven collection fibres, yielding a resolution improvement of about 30%. We believe that our implementation represents an attractive upgrade for existing confocal Raman microscopes that employ multi-line detectors.

Transmission and total internal reflection integrated digital holographic microscopy

Jianlin Zhao, Jiwei Zhang, Chaojie Ma, Siqing Dai, Jianglei Di, Ying Li, and Teli Xi

Doc ID: 268794 Received 22 Jun 2016; Accepted 14 Jul 2016; Posted 20 Jul 2016  View: PDF

Abstract: We develop a transmission and total internal reflection (TIR) integrated digital holographic microscopy (DHM) by introducing a home-made Dove prism with polished short side. With the help of angular and polarization multiplexing techniques, the two dimensional refractive index distribution of a specimen adhered on prism surface is determined using TIR-DHM. Meanwhile, the thickness profile is unambiguously calculated from the phase information using transmission DHM. This integrated microscopy is nondestructive and dynamic, and can be used to simultaneously measure the index distribution and thickness profile of transparent or semitransparent liquid or solid samples.

Photonic generation of phase-stable and wideband chirped microwave signals based on phase-locked dual optical frequency combs

Yi Dong, Yitian Tong, Qian Zhou, Daming Han, Weilin Xie, zhangweiyi Liu, Baiyu Li, Jie Qin, Xiaocheng Wang, and Weisheng Hu

Doc ID: 266845 Received 25 May 2016; Accepted 14 Jul 2016; Posted 19 Jul 2016  View: PDF

Abstract: A photonics-based scheme is presented for generating wideband and phase-stable chirped microwave signals based on two phase-locked combs with fixed and agile repetition rates. By tuning the difference of the two combs’ repetition rates and extracting different order comb tones, a wideband linearly frequency chirped microwave signal with flexible carrier frequency and chirped range is obtained. Owing to the scheme of dual heterodyne phase transfer and phase-locked loop, extrinsic phase drift and noise induced by the separated optical paths is detected and suppressed efficiently. Linearly frequency chirped microwave signals from 5 GHz to 15 GHz and 7 GHz to 247 GHz with 30 ms duration are achieved respectively, contributing to the time-bandwidth product of 3×108. And less than 1.3×10-5 linearity errors (RMS) are also obtained.

Bidirectional invisibility in Kramers-Krönig optical media

Stefano Longhi

Doc ID: 268511 Received 16 Jun 2016; Accepted 14 Jul 2016; Posted 19 Jul 2016  View: PDF

Abstract: A broad class of planar dielectric media with complex permittivity profiles that are fully invisible, for both left and right incidence sides, is introduced. Such optical media are locally isotropic, non-magnetic and belong to the recently discovered class of Kramers-Kronig media [Nature Photon. 9, 436 (2015)], i.e. the spatial profiles of the real and imaginary parts of the dielectric permittivity are related each other by a Hilbert transform. The transition from unidirectional to bidirectional invisibility, and the possibility to realize sharp reflection above a cut-off incidence angle, are also discussed.

Atmospheric tomography for artificial satellite observations with a single guide star

Michael Hart, Stuart Jefferies, and Douglas Hope

Doc ID: 267411 Received 01 Jun 2016; Accepted 14 Jul 2016; Posted 20 Jul 2016  View: PDF

Abstract: Estimation of wave-front errors in three dimensions is required to mitigate isoplanatic errors when using adaptive optics or numerical restoration algorithms to recover high-resolution images from blurred data taken through atmospheric turbulence. Present techniques rely on multiple beacons, either natural stars or laser guide stars, to probe the atmospheric aberration along different lines of sight, followed by tomographic projection of the measurements. In this paper we show that a three-dimensional estimate of the wave-front aberration can be recovered from measurements by a single guide star in the case where the aberration is stratifed, provided that the telescope tracks across the sky with non-uniform angular velocity. This is generally the case for observations of artificial earth-orbiting satellites, and the new method is likely to find application in ground-based telescopes used for space situational awareness.

Demonstration of gain saturation and double-pass amplification of 69.8 nm laser pumped by capillary discharge

liu tao, Yong-peng Zhao, wenhong zhang, Wei Li, and Huai-yu Cui

Doc ID: 267435 Received 06 Jun 2016; Accepted 14 Jul 2016; Posted 19 Jul 2016  View: PDF

Abstract: With the 45-cm-long capillary, we firstly obtained a saturated 69.8 nm laser with gain coefficient of 0.4 cm-1 and gain length product of 18. In order to increase the laser energy further, a double-pass amplification of 69.8 nm laser was firstly realized with a SiC mirror without coating. With the half cavity, the effective plasma column length and the effective gain length product can reach 84 cm and 33.7, respectively. The amplitude of laser pulse for double-pass amplification is 9 times larger than that for single-pass amplification. In addition, the full-width at half-maximum (FWHM) pulse width of laser pulse and FWHM divergence for single-pass amplification are 1.4 ns and 0.5 mrad, which increase to 2.2 ns and 3.4 mrad for double-pass amplification.

The Strehl ratio as the Fourier transform of a probability density

Miguel Alonso and Gregory Forbes

Doc ID: 267754 Received 06 Jun 2016; Accepted 14 Jul 2016; Posted 19 Jul 2016  View: PDF

Abstract: To give useful insight into the impact of mid-spatial frequency structure on optical performance, the Strehl ratio is shown to correspond to the Fourier transform of a simple statistical characterization of the phase aberration in the exit pupil. That statistical description is found simply by autocorrelating a histogram of the phase values. In practice, the histogram itself can often be approximated by a convolution of underlying histograms associated with fabrication steps and, together with the final autocorrelation, it follows from the Central Limit Theorem that the Strehl ratio as a function of the rms phase error is generally approximated well by a Gaussian.

WS2 as a saturable absorber for Q-switched 2 micron lasers

Shengzhi Zhao, Chao Luan, Kejian Yang, Jia Zhao, lei song, Tao Li, Hongwei Chu, junpeng qiao, Chao Wang, zhen li, shouzhen jiang, baoyuan man, and Lihe Zheng

Doc ID: 269033 Received 24 Jun 2016; Accepted 14 Jul 2016; Posted 19 Jul 2016  View: PDF

Abstract: We prepared WS2 nanosheets by using thermal decomposition method and demonstrated for the first time its nonlinear saturable absorption property at around 2 μm. With the as-prepared WS2 nanosheets as saturable absorber (SA), a passively Q-switched Tm:LuAG laser was realized successfully, and 660 ns laser pulses with an average output power of 1.08 W and pulse peak power of 26 W at a repetition rate of 63 kHz were obtained for an incident pump power of 7 W. Our experimental results definitely demonstrate that WS2 could be a kind of promising SA for solid-state 2 μm lasers. © 2015 Optical Society of America

Transverse magnetic field impact on waveguide modes of photonic crystals

Daria Sylgacheva, Nikolai Khokhlov, Andrey Kalish, SARKIS DAGESYAN, Alexander Shaposhnikov, Vladimir Berzhansky, Mohammad Alam, Mikhail Vasiliev, Kamal Alameh, Vladimir Belotelov, and Anatoly Prokopov

Doc ID: 269372 Received 29 Jun 2016; Accepted 14 Jul 2016; Posted 19 Jul 2016  View: PDF

Abstract: This Letter presents a theoretical and experimental study of waveguide modes of one-dimensional magneto-photonic crystals magnetized in the in-plane direction. It is shown that the propagation constants of the TM waveguide modes are sensitive to the transverse magnetization and, as a consequence, the spectrum of transverse magneto-optical Kerr effect has resonant features at mode excitation frequencies. Two types of structures are considered: a non-magnetic photonic crystal with an additional magnetic layer on top and a magneto-photonic crystal with a magnetic layer within each period. We found that the magneto-optical non-reciprocity effect is greater in the first case: it has magnitude δ ~10-4 while the second structure type demonstrates δ ~10-5 only, due to the higher asymmetry of the claddings of the magnetic layer. Experimental observations show resonant features in the optical and magneto-optical Kerr effect spectra for both considered types of the magneto-photonic crystals. The measured dispersion properties are in good agreement with the theoretical predictions. Amplitude of light intensity modulation due to Kerr effect of up to 2.5% was observed for waveguide mode excitation within the magnetic top layer of the non-magnetic photonic crystal structure. The presented theoretical approach may be utilized for the design of magneto-optical sensors and modulators requiring pre-determined spectral features.

Dual-wavelength diode laser with electrically adjustable wavelength distance at 785 nm

Bernd Sumpf, Julia Kabitzke, Jörg Fricke, Peter Ressel, André Mueller, Martin Maiwald, and Guenther Traenkle

Doc ID: 268592 Received 17 Jun 2016; Accepted 12 Jul 2016; Posted 13 Jul 2016  View: PDF

Abstract: A spectrally adjustable monolithic dual-wavelength diode laser at 785 nm as excitation light source for shifted excitation Raman difference spectroscopy (SERDS) is presented. The spectral distance between the two excitation wavelengths can be electrically adjusted between 0 nm and 2.0 nm using implemented heater elements above the DBR-gratings. Output powers up to 180 mW at a temperature of 25°C were measured. The spectral width is smaller than 13 pm limited by the spectrum analyzer. The device is well-suited for Raman spectroscopy and the flexible spectral distance allows a target-specific adjustment of the excitation light source for SERDS.

Attosecond photoelectron streaking with enhanced energy resolution for small-bandgap materials

Alexander Guggenmos, Ayman Akil, Marcus Ossiander, Martin Schäffer, Abdallah Azzeer, Gerhard Boehm, Markus Amann, Reinhard Kienberger, Martin Schultze, and Ulf Kleineberg

Doc ID: 269551 Received 30 Jun 2016; Accepted 12 Jul 2016; Posted 13 Jul 2016  View: PDF

Abstract: Attosecond photoelectron streaking spectroscopy allows to time resolve electron dynamics with a temporal resolution approaching the atomic unit of time. Studies have been performed in numerous systems including atoms, molecules and surfaces and the quest for ever higher temporal resolution called for ever wider spectral extent of the attosecond pulses. For typical experiments relying on attosecond pulses with a duration of 200 attoseconds the time-bandwidth limitation for a Gaussian pulse implies a minimal spectral bandwidth larger than 9 eV translating to a corresponding spread of the detected photoelectron kinetic energies. Here, by utilizing a specially tailored narrowband reflective XUV multilayer mirror, we explore experimentally the minimal spectral width compatible with attosecond time resolved photoelectron spectroscopy while obtaining the highest possible spectral resolution. The validity of the concept is proven by recording attosecond electron streaking traces from the direct semiconductor gallium arsenide (GaAs), with a nominal bandgap of 1.42 eV at room temperature, proving the potential of the approach for tracking charge dynamics also in these technologically highly relevant materials that previously have been inaccessible to attosecond science.

Scattering of surface plasmon-polaritons and volume waves by a rough gold film

Valeriy Sterligov, Iaroslav Grytsaenko, and Yakiv Men

Doc ID: 268116 Received 21 Jun 2016; Accepted 11 Jul 2016; Posted 11 Jul 2016  View: PDF

Abstract: A discrepancy between the theories of volume and surface plasmon-polaritons (SPPs) waves’ scattering was found. Its tentative explanation is related to the resonance like emission of SPPs energy due to SPPs diffraction by a surface relief Fourier decomposition component. It was also shown that the sum of surface waves’ scattered intensity along a plane of incidence is proportional to surface roughness value.

Time-encoded structured illumination microscopy -towards ultra-fast super resolution imaging

Yuxi Wang, Qiang Guo, Hongwei Chen, Sigang Yang, Minghua Chen, and Shizhong Xie

Doc ID: 268519 Received 17 Jun 2016; Accepted 10 Jul 2016; Posted 18 Jul 2016  View: PDF

Abstract: An imaging strategy based on optical time-encoded structured illumination microscopy (TE-SIM) opens the way towards ultra-fast super-resolution imaging. A proof-of-principle experiment is conducted and the introduced TE-SIM accelerates the generation rate of sinusoidal fringe patterns to an unprecedented speed (dozens of megahertz). At such a high speed, super resolution imaging that surpasses the diffraction limit by a factor of 1.4 is demonstrated. This imaging strategy with high temporal and spatial resolution has great potential in many exciting applications, such as dynamic live cell imaging or high-throughput screening.

Phase-locking transition in Raman combs generated with whispering gallery mode resonators

Guoping Lin and Yanne Chembo

Doc ID: 264747 Received 09 May 2016; Accepted 08 Jul 2016; Posted 11 Jul 2016  View: PDF

Abstract: We investigate the mechanisms leading to phase-locking in Raman optical frequency combs generated with ultra-high Q crystalline whispering gallery mode disk-resonators. We show that several regimes can be triggered depending on the pumping conditions, such as single frequency Raman lasing, multimode operation involving more than one family of cavity eigenmodes, and Kerr-assisted Raman frequency comb generation. The phase-locking and coherence of the combs are experimentally monitored through the measurement of beat signal spectra. These phase-locked combs which feature high coherence and wide spectral spans, are obtained with pump powers in the range of few tens of mW. In particular, Raman frequency combs with multiple free-spectral range spacings are reported, and the measured beat signal in the microwave domain features a 3 dB linewidth smaller than 50 Hz, thereby indicating phase-locking.


Laura Corner and Robert Shalloo

Doc ID: 265208 Received 02 Jun 2016; Accepted 07 Jul 2016; Posted 11 Jul 2016  View: PDF

Abstract: We present a double unbalanced Michelson interferometer producing up to 4 output pulses from a single input pulse. The interferometer is stabilized with the Hänsch-Couillard method using an auxiliary low power continuous wave laser injected into the interferometer, allowing the stabilization of the temporal jitter of the output pulses to 0.02fs. Such stabilized pulse trains would be suitable for driving multi-pulse laser wakefield accelerators and the technique could be extended to include amplification in the arms of the interferometer.

Kerr self-cleaning of femtosecond-pulsed beams in graded-index multimode fiber

Zhanwei Liu, Logan Wright, Demetrios Christodoulides, and Frank Wise

Doc ID: 267907 Received 08 Jun 2016; Accepted 07 Jul 2016; Posted 13 Jul 2016  View: PDF

Abstract: We observe a nonlinear spatial self-cleaning process for femtosecond pulses in graded-index (GRIN) multimode fiber (MMF). Pulses with ~ 80 femtosecond duration at 1030 nm are launched into GRIN MMF with 62.5 mm core. The near-field beam profile at the output end of the fiber evolves from a speckled pattern to a centered, bell-shaped transverse structure with increasing pulse energy. The experimental observations agree well with numerical simulations, which show that the Kerr nonlinearity underlies the process. This self-cleaning process may find applications in saturable absorbers, ultrafast pulse generation, and beam combining.

Generating Attenuation-Resistant Frozen Waves in Absorbing Fluid

Ahmed Dorrah, Michel Zamboni-Rached, and Mo Mojahedi

Doc ID: 268641 Received 22 Jun 2016; Accepted 06 Jul 2016; Posted 07 Jul 2016  View: PDF

Abstract: We experimentally demonstrate a class of non-diffracting beams, called Frozen Waves, with central spot that can be made to maintain a predefined intensity profile while propagating in an absorbing fluid. Frozen Waves are composed of Bessel beams with different transverse and longitudinal wavenumbers, and are generated using a programmable spatial light modulator. The attenuation-resistant Frozen Waves demonstrated here address the problem of propagation losses in absorbing media. This can potentially benefit many applications in particle micro-manipulation, data communications, remote sensing, and imaging.

Extremely small wavevector regime in one-dimensional photonic crystals for angular transmission filters

Hideo Iizuka, Nader Engheta, and Shinya Sugiura

Doc ID: 269042 Received 24 Jun 2016; Accepted 06 Jul 2016; Posted 07 Jul 2016  View: PDF

Abstract: One-dimensional photonic crystals (PCs), when operating near the band edge in the dispersion diagram, inherently possess nearly polarization-independent angular selectivity; an angular transmission window around the normal direction with reflection for other angles. However, the incident light is mostly reflected at the PC-air interface due to large impedance mismatch in such an extremely small wavevector regime. We show that the reflection may be sufficiently suppressed by utilizing a specially designed antireflection structure consisting of a PC having a different pitch from that of the host PC. The wave impedance of PCs is dependent on local observation points. The underlying mechanism is that the interfaces of the antireflection PC with the host PC and the air structure are selected such that the transverse impedance has a real value, which is positioned at the center of the thickness of a material film. Moreover, our structure provides a high-throughput wide angular transmission window including the normal direction in both s- and p-polarizations, which is desired for many applications scenarios. We develop an analytical model that captures the angular selectivity observed in numerical results.

Topological interface states in multiscale spoof-insulator-spoof waveguides

Dezhuan Han, Yan Meng, Hong Xiang, Ruo-Yang Zhang, Xiaoxiao Wu, Che Ting Chan, and Weijia Wen

Doc ID: 264725 Received 06 May 2016; Accepted 25 Jun 2016; Posted 27 Jun 2016  View: PDF

Abstract: The spoof-insulator-spoof (SIS) structure can serve as a waveguide for spoof surface plasmon polaritons (spoof SPPs). If a periodic geometry modulation in the wavelength scale is introduced to the SIS waveguide, this multiscale SIS (MSIS) waveguide possesses band gaps for spoof SPPs analogous to the band gaps in a photonic crystal. Inspired by the topological interface states found in photonic crystals, we construct an interface by connecting two MSIS waveguides with different topological properties (inverted Zak phases of bulk bands). The topological interface states in the MSIS waveguides are observed experimentally. The measured decay lengths of the interface states agree excellently with the numerical results. These localized interface states may find potential applications in miniaturized microwave devices.

Subwavelength imaging of point source based on two-dimensional photonic crystals

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

Doc ID: 267554 Received 03 Jun 2016; Accepted 23 Jun 2016; Posted 23 Jun 2016  View: PDF

Abstract: A new two-dimensional (2D) photonic crystal (PC) structure with effective refractive index approaching -1 is proposed, consisting of periodic array air holes in silicon. The light radiated from a point source can form an image through a single wedge PC. Numerical results show that the half-width of the image reaches 0.44λ, which is lower than the half of incident wavelength. In addition, the light through the combination of two same PCs can also form a subwavelength imaging of which half-width reaches 0.67λ, and the image almost flipped 180°compared with point source. © 2016 Optical Society of America

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