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Dark-field Brillouin microscopy

Giuseppe Antonacci

Doc ID: 283328 Received 21 Dec 2016; Accepted 20 Jan 2017; Posted 23 Jan 2017  View: PDF

Abstract: Brillouin microscopy is a non-contact and label-free technique for mapping fundamental micro-mechanical properties in the volume of biological systems. Specular reflections and elastic scattering easily overwhelm the weak Brillouin spectra due to the limited extinction of virtually imaged phased array (VIPA) spectrometers, thereby affecting the image acquisition. In this Letter, we demonstrate a dark-field method to reject the elastic background light using an annular illumination and a confocal detection. To validate our method, images of polystyrene and liquid samples were obtained using both a confocal and the dark-field system. An extinction ratio of 30 dB was readily achieved.

INTERROGATION OF METABOLIC AND OXYGEN STATES OF TUMORS WITH FIBER-BASED LUMINESCENCE LIFETIME SPECTROSCOPY

Vladislav Shcheslavskiy, Maria Lukina, Anna Orlova, Marina Shirmanova, Daniil Shirokov, Anton Pavlikov, Antje Neubauer, Hauke Studier, Wolfgang Becker, Elena Zagaynova, Toshidata Yoshihara, and Seiji Tobita

Doc ID: 282199 Received 06 Dec 2016; Accepted 19 Jan 2017; Posted 23 Jan 2017  View: PDF

Abstract: The study of metabolic and oxygen states of cells in a tumor in vivo is crucial for understanding of the mechanisms responsible for the tumor development and provides background for the relevant tumor’s treatment. Here, we show that a specially designed implantable fiber-optical probe provides a promising tool for optical interrogation of metabolic and oxygen states of a tumor in vivo. In our experiments, the excitation light from a ps diode laser source is delivered to the sample through an exchangeable tip via a single mode fiber, and the emission light is transferred to the detector by another multimode fiber. Fluorescence lifetime of nicotinamid adenine dinucleotide (NAD(P)H) and phosphorescence lifetime of an oxygen sensor based on iridium (III) complex of enzothienylpyridine (BTPDM1) are explored both in model experiment in solutions, and in living mice.

Simple interrogator for optical fiber-based white light Fabry-Pérot interferometers

Zhihao Yu, Zhipeng Tian, and Anbo Wang

Doc ID: 282492 Received 08 Dec 2016; Accepted 19 Jan 2017; Posted 19 Jan 2017  View: PDF

Abstract: In this letter, we present the design of a simple signal interrogator for optical fiber-based white light Fabry-Pérot (F-P) interferometers. With the hardware being composed of only a flat fused silica wafer and a CCD camera, this interrogator translates the spectral interference into a spatial interference pattern, and then demodulates the F-P cavity length with the use of a relatively simple demodulation algorithm. The concept is demonstrated experimentally in a fiber optic sensor with a sapphire wafer as the F-P cavity.

Soliton repetition rate in a silicon-nitride microresonator

Chengying Bao, Andrew Weiner, Minghao Qi, Cong Wang, Jose Jaramillo-Villegas, Yi Xuan, and Daniel Leaird

Doc ID: 280577 Received 15 Nov 2016; Accepted 19 Jan 2017; Posted 23 Jan 2017  View: PDF

Abstract: The repetition rate of a Kerr comb comprising a single soliton in an anomalous dispersion silicon nitride microcavity is measured as a function of pump frequency tuning. The contributions from the Raman soliton self-frequency shift (SSFS) and from thermal effects are evaluated both experimentally and theoretically; the SSFS is found to dominate the changes in repetition rate. The relationship between the changes in repetition rate and pump frequency detuning is found to be independent of the nonlinearity coefficient and dispersion of the cavity. Modeling of the repetition rate change by using the generalized Lugiato-Lefever equation is discussed; the Kerr shock is found to have only a minor effect on repetition rate for cavity solitons with duration down to ~50 fs.

Channel-selective wavelength conversion of quadrature amplitude modulation signal using a graphene assisted silicon microring resonator

Yun Long, Xiao Hu, mengxi ji, Li Shen, Andong Wang, Yi Wang, and Jian Wang

Doc ID: 281730 Received 29 Nov 2016; Accepted 19 Jan 2017; Posted 23 Jan 2017  View: PDF

Abstract: Compact and flexiable all-optical signal processing is highly desirable in future optical networks for its high-speed processing without optical-electrical-optical conversion. Recent progress of silicon photonics and graphene has driven the increasing research interest of ultra-compact high efficient chip-scale all-optical signal processing. In the letter, by exploiting a graphene assisted silicon microring resonator (GSMR), we propose and experimentally demonstrate channel-selective wavelength conversion of multi-channel quadrature amplitude modulation (QAM) signal. Efficient selective conversion of four-channel 16-QAM signal are observed. The selective suppression ratio and bit-error rate of selective conversion are studied showing favorable operation performance. The proposed channel-selective wavelength conversion of multi-channel signal using GSMR may find various applications in future advanced optical networks for robust data management.

1.55 μm free-space active polarimetric imager by orthogonality breaking sensing

François PARNET, Julien FADE, Noé Ortega-Quijano, Goulc'hen Loas, Ludovic Frein, and Mehdi Alouini

Doc ID: 281961 Received 08 Dec 2016; Accepted 19 Jan 2017; Posted 19 Jan 2017  View: PDF

Abstract: We report the design and optimization of an active polarimetric imaging demonstrator operating at 1.55 µm and based on the orthogonality breaking technique. It relies on the use of a fibered dual-frequency dual-polarization source raster scanned over the scene. A dedicated opto-electronic detection chain is developed in order to demodulate the optical signal backscattered at each location of the scene in real time, providing multivariate polarimetric image data in one single scan and with limited acquisition time. We experimentally show on a homemade scene that contrast maps can be built to reveal hidden dichroic objects over a depolarizing background, as well as their orientation. Finally, experiments through air turbulence illustrate the benefit of such an imaging architecture over standard polarimetric techniques requiring multiple image acquisitions.

Graphene-based Solitons for Spatial Division Multiplexed Switching

Jonathan George and Volker Sorger

Doc ID: 281982 Received 01 Dec 2016; Accepted 18 Jan 2017; Posted 19 Jan 2017  View: PDF

Abstract: Spatial division multiplexing utilizes the directionality of light’s propagating k-vector to separate it into distinct spatial directions. Here we show that the anisotropy of orthogonal spatial Solitons propagating in a single Graphene monolayer results in phase-based multiplexing. We use the self-confinement properties of spatial Solitons to increase the usable density of states (DOS) of this switching-system. Furthermore, we show that crossing two orthogonal Solitons exhibit a low (0.035 dB) mutual disturbance from another enabling independent k-vector switching. The efficient utilization of the DOS and multiplexing in real-space enables data processing parallelism with applications in optical networking and computing.

A linearly polarized low-noise Brillouin random fiber laser

Liang Zhang, Yanping Xu, Song Gao, Bhavaye Saxena, Liang Chen, and Xiaoyi Bao

Doc ID: 280386 Received 09 Nov 2016; Accepted 18 Jan 2017; Posted 19 Jan 2017  View: PDF

Abstract: A linearly polarized Brillouin random fiber laser (LP-BRFL) with distributed feedback along 2-km polarization maintaining fibers (PMFs) is demonstrated. The laser was built up using a bidirectional pumping mechanism in an all-PMF configuration, yielding a radiation with 8% power efficiency and more than 25dB polarization extinction ratio (PER). A high lasing efficiency is achieved due to the polarization matched Brillouin amplification and distributed feedback along km-long PMFs. The relative intensity noise (RIN) and the thermal-induced frequency noise of this random laser has also been measured and compared to that of a custom single mode fiber (SMF) based random laser and a conventional phase locked laser.

Laboratory simulation of laser propagation through plasma sheaths containing ablation particles of ZrB2-SiC-C during hypersonic flight

Qing Zang, Xingxing Bai, Ping Ma, Jie Huang, Ma Jing, Siyuan Yu, Hongyan Shi, Xiudong Sun, Yang Liu, and Yueguang Lu

Doc ID: 280530 Received 25 Nov 2016; Accepted 18 Jan 2017; Posted 19 Jan 2017  View: PDF

Abstract: The optical communication method is of potentials for solving the blackout problem which is a big challenge faced with the development of aerospace. Two laser transmission systems are set up to explore the influence of the plasma and the ablation particles on the propagation of the laser. The experimental results indicate that the laser can transmit through the plasma with little attenuation. When there are ablation particles of ZrB2-SiC-C added in the plasma, the intensity of laser has fluctuations. The work introduced in this letter can be regarded as a basic research of the propagation characters of the laser through plasma sheaths.

Diode-end-pumped Ho,Pr:LiLuF4 bulk laser at 2.95 µm

Baitao Zhang, hongkun nie, Peixiong Zhang, Kejian Yang, Tao Li, Shuaiyi Zhang, Yin Hang, Jingliang He, Lianhan Zhang, and Jianqiu Xu

Doc ID: 282932 Received 15 Dec 2016; Accepted 18 Jan 2017; Posted 19 Jan 2017  View: PDF

Abstract: A diode-end-pumped continuous-wave (CW) and passively Q-switched Ho,Pr:LiLuF4 (Ho,Pr:LLF) laser operation at 2.95 µm was demonstrated for the first time, to the best of our knowledge. A maximum CW output power of 172 mW was generated with a slope efficiency of 6%. By using a monolayer graphene as the saturable absorber (SA), the passively Q-switched operation was realized, in which regime the highest output power, the shortest pulse duration, and the maximum repetition rate were determined to be 88 mW, 937.5 ns, 55.7 kHz, respectively. The laser beam quality factor M2 were measured to be M2x=1.48 and M2y=1.47.

Positive and negative curvatures nested in antiresonant hollow-core fiber

Md. Imran Hasan, Nail Akhmediev, and Wonkeun Chang

Doc ID: 280686 Received 11 Nov 2016; Accepted 17 Jan 2017; Posted 17 Jan 2017  View: PDF

Abstract: We propose a negative-curvature hollow-core fiber that has an elliptical nested element in the antiresonant tubes. The additional elliptical element effectively adds two curvatures, namely a positive and a negative curvature. Our numerical study shows that it enhances the confinement of the light in the core. Moreover, the nested elements provide an extra degree of freedom that can be exploited for suppressing higher-order modes through the change of the ellipticity. The resulting low confinement loss and single-mode guidance properties of the proposed fiber make it a suitable candidate for applications in ultrashort pulse delivery and gas-based nonlinear systems.

Picosecond kHz-class cryogenically-cooled multistage Yb-doped chirped pulse amplifier

Darren Rand, Tso Yee Fan, Daniel Miller, and Francis Morrissey

Doc ID: 282057 Received 02 Dec 2016; Accepted 17 Jan 2017; Posted 17 Jan 2017  View: PDF

Abstract: A multistage cryogenic chirped pulse amplifier has been developed, utilizing two different Yb-doped gain materials in subsequent amplifier stages. A Yb:GSAG regenerative amplifier followed by a Yb:YAG power amplifier is able to deliver pulses with a broader bandwidth than a system using only one of these two gain media throughout. We demonstrate 90 mJ pulse energy (113 W average power) uncompressed and 67 mJ (84 W average power) compressed at 1.25 kHz pulse repetition frequency, 3.0 ps FWHM Gaussian pulse width, and near-diffraction-limited (M2 < 1.3) beam quality.

Parametric Amplification of 100-fs Mid-IR Pulses in ZnGeP₂ Driven by a Ho:YAG Chirped Pulse Amplifier

Tsuneto Kanai, Pavel Malevich, Sarayoo Kangaparambil, Kakuta Ishida, Makoto Mizui, Kaoru Yamanouchi, Heinar Hoogland, Ronald Holzwarth, Audrius Pugzlys, and Andrius Baltuska

Doc ID: 282450 Received 13 Dec 2016; Accepted 17 Jan 2017; Posted 17 Jan 2017  View: PDF

Abstract: We report on the parametric generation of 100-fs sub-6-cycle 40 μJ pulses with the center wavelength at 5.2 μm using a 1-ps 2.1-μm pump laser and a dispersion management scheme based on bulk material. Our optically synchronized amplifier chain consists of a Ho:YAG chirped-pulse amplifier (CPA) and white-light-seeded optical parametric amplifiers (OPA) providing simultaneous passive carrier-envelope phase (CEP) locking of three ultrashort longwave pulses at the pump, signal and idler wavelengths corresponding, respectively, to 2.1, 3.5, and 5.2 μm. We also demonstrate bandwidth enhancement and efficient control over nonlinear spectral phase in the regime of cascaded χ² nonlinearity in ZnGeP₂ (ZGP).

High average power nonlinear compression to 4 GW, sub-50 fs pulses at 2 μm wavelength

Martin Gebhardt, Christian Gaida, Fabian Stutzki, Steffen Hädrich, Cesar Jauregui, Jens Limpert, and Andreas Tünnermann

Doc ID: 281948 Received 06 Dec 2016; Accepted 16 Jan 2017; Posted 23 Jan 2017  View: PDF

Abstract: The combination of high repetition rate ultrafast thulium-doped fiber laser systems and gas-based nonlinear pulse compression in waveguides offers promising opportunities for the development of few-cycle laser sources. These can simultaneously deliver high peak powers and high average powers at around 2 µm wavelength. In this work, we report on a nonlinear pulse compression stage delivering 252 µJ-, sub-50 fs-pulses at 15.4 W of average power. This performance level was enabled by actively mitigating ultrashort-pulse propagation effects induced by the presence of water-vapor absorptions.

An extended temporal cloak based on inverse temporal Talbot effect

Bowen Li, Xie Wang, Jiqiang Kang, Yuan Wei, Toni Yung, and Kenneth Kin-Yip Wong

Doc ID: 283434 Received 22 Dec 2016; Accepted 16 Jan 2017; Posted 23 Jan 2017  View: PDF

Abstract: A temporal cloak with significantly extended cloaking window and spatial distribution is created using inverse temporal Talbot effect. The continuously cloaking window and total cloaking ratio is 196 ps and 75%, respectively, which is 5.4 and 1.6 times larger than previous record. Another distinctive feature of our new scheme, the cloak is roughly maintained over 5-km of dispersion-compensating fiber, which provides the capability of cloaking temporal events happening at multiple positions simultaneously. To demonstrate the cloaking performance, both message-encoded and pseudo-random temporal events are successfully concealed. Last but not least, since our configuration does not require opposite sign of dispersion, the idea can be applied analogously to the spatial domain according to space-time duality, thus also enriching the spatial cloaking technique.

Acceleration of the Nonlinear Dynamics in P-Doped Indium Phosphide Nanoscale Resonators

Gregory Moille, Sylvain Combrié, Kerstin Fuchs, Matusala Jacob, Johann Reithmaier, and Alfredo De Rossi

Doc ID: 282981 Received 15 Dec 2016; Accepted 16 Jan 2017; Posted 17 Jan 2017  View: PDF

Abstract: We demonstrated a two-fold acceleration of the fast time constant characterizing the recovery of a p-doped Indium-Phosphide Photonic Crystal all-optical gate. Time-resolved spectral analysis is compared with a three-dimensional drift-diffusion model for the carrier dynamics, demonstrating the transition from the am- bipolar to the faster minority carrier dominated diffu- sion regime. This open the perspective for faster yet efficient nanophotonic all-optical gates.

Simulating the Space-charge Field Formation in Thermally Poled Optical Fibers: New Two Rate Model for Hydrogenated Cations

Lin Huang, Honglin An, Guobin Ren, and Simon Fleming

Doc ID: 280806 Received 16 Nov 2016; Accepted 16 Jan 2017; Posted 18 Jan 2017  View: PDF

Abstract: In thermally poled optical fibers the second-order nonlinearity has been observed to be distributed in a narrow layer more than 10 microns beneath the anode surface, a result that cannot be explained by current models. In this letter we propose a new model based on slow migration of H₃O+ and fast H+ migration related to H₃O+ concentration. Numerical simulation results show a narrow layer-shaped distribution of the induced second-order nonlinearity, which retains its magnitude and distribution profile in the migration process, and is in good agreement with experimental observations.

Stimulated Raman scattering microscopy and spectroscopy with a rapid scanning optical delay line

Minbiao Ji, Ruoyu He, Zhiping Liu, Yongkui Xu, Wei Huang, and Hong Ma

Doc ID: 280814 Received 18 Nov 2016; Accepted 16 Jan 2017; Posted 18 Jan 2017  View: PDF

Abstract: Stimulated Raman scattering (SRS) microscopy that is capable of both high speed imaging and rapid spectroscopy will be advantageous for detailed chemical analysis of heterogeneous biological specimens. We have developed a system based on spectral focusing SRS technology, with the integration of a rapid scanning optical delay line, which allows continuous tuning of SRS spectra by scanning a galvo mirror. We demonstrated SRS spectral measurements of dimethyl sulfoxide solution at low concentrations, and multi-color imaging of rice pollens and HeLa cells with line-by-line delay tuning to reduce motion artifacts, as well as fast acquisition of SRS spectra at specific regions of interest.

716 nm deep-red passively Q-switched Pr:ZBLAN fiber laser using carbon-nanotube saturable absorber

Zhiping Cai, Wensong Li, Tuanjie Du, Jinglong Lan, Changlei Guo, Yongjie Cheng, Huiying Xu, chunhui zhu, Frank (Fengqiu) Wang, and Zhengqian Luo

Doc ID: 280255 Received 07 Nov 2016; Accepted 16 Jan 2017; Posted 17 Jan 2017  View: PDF

Abstract: We experimentally demonstrated a compact single-wall carbon nanotube (SWNT) based deep-red passively Q-switched Pr3+-doped ZBLAN all-fiber laser operating at 716 nm. A free-standing SWNT/polyvinyl alcohol (PVA) composite film embedded between a pair of fiber connectors was employed as a saturable absorber (SA). The deep-red Q-switched operation is attributed to the combination of implementing a pair of fiber end-facet mirrors to achieve the linear laser resonator, and incorporating a SWNT-SA into the cavity as a Q-switcher. Stable short-pulse generation with a duration of 2.3 µs was realized. When gradually increasing the incident pump power, the pulse repetition rate can be linearly tuned from 32.6 to 86.5 kHz, corresponding to a maximum average output power of 1.5 mW and a highest single pulse energy of 18.3 nJ. This is, to the best of our knowledge, the first demonstration of SWNT-based SA for Q-switched laser at deep-red wavelength ~ 716 nm.

Optical Neutrality: Invisibility without Cloaking

Maxim Durach, Reed Hodges, and Cleon Dean

Doc ID: 282626 Received 13 Dec 2016; Accepted 15 Jan 2017; Posted 17 Jan 2017  View: PDF

Abstract: We show that it is possible to design an invisible wavelength-sized metal-dielectric metamaterial object without evoking cloaking. Our approach is an extension of the neutral inclusion concept by Zhou and Hu [Phys.Rev.E 74, 026607 (2006)] to Mie scatterers. We demonstrate that an increase of metal fraction in the metamaterial leads to a transition from dielectric-like to metal-like scattering, which proceeds through invisibility or optical neutrality of the scatterer. Formally this is due to cancellation of multiple scattering orders, similarly to plasmonic cloaking introduced by Alu and Engheta [Phys.Rev.E 72, 0166 (2005)], but without introduction of the separation of the scatterer into cloak and hidden regions.

Full-field Functional Optical Angiography

Zeng Yaguang, Wenjian Mao, Caizhong Guan, Guanping Feng, Haishu Tan, Dingan Han, and Mingyi Wang

Doc ID: 282158 Received 08 Dec 2016; Accepted 14 Jan 2017; Posted 17 Jan 2017  View: PDF

Abstract: We propose full-field functional optical angiography for a live biological specimen based on the absorption intensity fluctuation modulation (AIFM) effect. Because of the difference in absorption between red blood cells (RBCs) and the background tissue under low-coherence light illumination, the moving RBCs, which discontinuously pass though the capillary vessels, generate an AIFM effect. This effect shares the sensitivity of low-coherence interference and the high contrast of absorption imaging between RBCs and the background tissue. It is used to highlight the RBC signal from the background tissue. The averaged and real-time modulation depth is computed to simultaneously obtain full-field label-free optical angiography and blood flow velocity (BFV) measurements. Our experimental results could potentially be applied in blood circulation system studies for fundus imaging.

Resonant forward scattering of light by high refractive-index dielectric nanoparticles with toroidal dipole contributions

Pavel Terekhov, Kseniia Baryshnikova, alexander sahlin, and Andrey Evlyukhin

Doc ID: 282438 Received 27 Dec 2016; Accepted 14 Jan 2017; Posted 23 Jan 2017  View: PDF

Abstract: In this Letter we demonstrate theoretically that the resonant excitation of toroidal dipole moment of silicon nanoparticles by incident light can provide strong suppression of the backward light scattering and, simultaneously, resonant forward light scattering. This effect is realized due to the field interference between the scattered waves generated by electric, magnetic and toroidal dipole moments of silicon nanoparticles and can be observed for other high-refractive index dielectric nanoparticles depending on their size and aspect-ratio.

1.55 μm band low threshold, continuous wave lasing from InAs/InAlGaAs quantum dot microdisks

si zhu, Bei Shi, yating wan, Evelyn Hu, and Kei May Lau

Doc ID: 278755 Received 17 Oct 2016; Accepted 13 Jan 2017; Posted 17 Jan 2017  View: PDF

Abstract: InAs/InAlGaAs quantum dot active layers within micro-cavity resonators offer the potential of ultra-low threshold lasing in the 1.5 μm telecom window. Here, we demonstrate the first quantum dot microdisk laser with single-mode emission around 1.55 μm under continuous wave optical pumping up to 170 K. The extracted threshold is as low as 32 μW at 77 K, favorably compared to the state-of-the-art quantum well microdisk counterparts. This result represents a critical step toward low threshold and highly compact monolithically integrable light emitting source for fiber communication.

Laser crater enhanced Raman scattering

Vasily Lednev, Pavel Sdvizhenskii, Mikhail Grishin, Mikhail Filippov, Alexander Shchegolikhin, and Sergey Pershin

Doc ID: 282763 Received 15 Dec 2016; Accepted 12 Jan 2017; Posted 13 Jan 2017  View: PDF

Abstract: Raman signal enhancement by multiple scattering inside laser crater cones was observed for the first time. Laser crater enhanced Raman spectroscopy (LCERS) yielded a 14-fold increase in the Raman spectra bands due to efficient multiple scattering of laser irradiation within the laser crater walls. The same pulsed Nd:YAG laser (532 nm, 10 ns) was used for both laser crater formation and Raman scattering experiments by varying the output pulse energy. First, powerful pulses are used to produce the laser crater and then low energy pulses are used to perform Raman scattering measurements. The laser crater profile and its alignment with the laser beam waist were found to be the key parameters for the optimization of the Raman bands intensity enhancement. Raman intensity enhancement resulted from increased surface scattering area at the crater walls rather than spatially offset Raman scattering. The increased signal-to-noise ratio resulted in limits of detection improvement for quantitative analysis using LCERS

Phase retrieval in multi-core fiber bundles

Dan Oron, Dani Kogan, Siddharth Sivankutty, Viktor Tsvirkun, Geraud Bouwmans, Esben Andresen, and Herve Rigneault

Doc ID: 276279 Received 19 Oct 2016; Accepted 12 Jan 2017; Posted 13 Jan 2017  View: PDF

Abstract: Multi-core fiber bundles are widely used in endoscopy due to their miniature size and their direct imaging capabilities. They have recently been used, in combination with spatial light modulators, in various realizations of endoscopy with little or no optics at the distal end. These schemes require characterization of the relative phase offsets between the different cores, typically done using off-axis holography thus requiring both an interferometric setup and typically access to the distal tip. Here we explore the possibility to employ phase retrieval to extract the necessary phase information. We show that in the noise-free case, disordered fiber bundles are superior for phase retrieval over their periodic counterparts, and demonstrate experimentally accurate phase information for up to ten simultaneously illuminated cores. Phase retrieval is thus presented as a viable alternative for real-time monitoring of phase distortions in multi-core fiber bundles.

Acoustic emission sensor system using chirped fiber-Bragg-grating Fabry-Perot interferometer and smart feedback control

Ming Han, Guigen Liu, Yupeng Zhu, Xiangyu Luo, and Qi Zhang

Doc ID: 281164 Received 18 Nov 2016; Accepted 12 Jan 2017; Posted 17 Jan 2017  View: PDF

Abstract: We demonstrate a fiber-optic acoustic emission (AE) sensor system that is capable of performing AE detection even when the sensor is experiencing large quasi-static strains. The sensor is a Fabry-Perot interferometer formed by cascaded chirped fiber-Bragg gratings (CFBGs). The reflection spectrum of the sensor features a number of narrow spectral notches equally spaced within the reflection bandwidth of the CFBG. A semiconductor laser whose wavelength can be fast tuned through current injection is used to lock the laser line to the center of a slope of a spectral notch. When the notch is knocked out of the tuning range of the laser, a neighboring notch moves into the range. Through a smart feedback control scheme, the laser is unlocked from current spectral lock and re-locked to desired point of the new notch. The fast speed of the unlocking/relocking process ensures that AE signal is monitored without significant disruption. © 2016 Optical Society of America

Femtosecond Two-Photon Laser-Induced Fluorescence of Krypton for High-Speed Flow Imaging

Waruna Kulatilaka, Yejun Wang, and Cade Capps

Doc ID: 282655 Received 16 Dec 2016; Accepted 12 Jan 2017; Posted 17 Jan 2017  View: PDF

Abstract: Ultrashort-pulse (femtosecond-duration) two-photon laser-induced fluorescence (fs-TPLIF) of an inert gas tracer krypton is investigated. A comprehensive spectroscopic study of fluorescence channels followed by the 5p’←←4p excitation of Kr at 204.1 nm is reported. The experimental line positions in the 750–840-nm emission region agree well with the NIST Atomic Spectra Database. The present work provides an accurate listing of relative line strengths in this spectral region. In the range of laser pulse energies investigated, a quadratic dependence was observed between the Kr-TPLIF signal and the laser pulse energy. The single-laser-shot 2D TPLIF images recorded in an unsteady jet demonstrate the potential of using fs excitation at 204.1 nm for mixing and flow diagnostic studies using Kr as an inert gas tracer. © 2016 Optical Society of America

Methane based in situ temperature rise measurement in diode pumped rubidium laser

Hongyan Wang, Rui Wang, Zining Yang, and Xiaojun Xu

Doc ID: 282306 Received 06 Dec 2016; Accepted 11 Jan 2017; Posted 12 Jan 2017  View: PDF

Abstract: We measured active zone temperature rise of an operational diode pumped rubidium laser non-perturbatively with standard near infrared methane tunable diode laser spectroscopy (TDLAS). For a Rb+ methane DPAL, the temperature rise was obtained. Especially, the temperature difference (~10K) between lasing and un-lasing cases were well identified, which demonstrated a high temperature detection resolution of the method. To our knowledge, this is the first demonstration of extending methane TDLAS spectroscopy to DPALs’ study.

A simple fibre based solution for coherent multidimensional spectroscopy in the visible regime

Patanjali Kambhampati, Helne Seiler, Samuel Palato, and Bruno Schmidt

Doc ID: 282370 Received 09 Dec 2016; Accepted 11 Jan 2017; Posted 12 Jan 2017  View: PDF

Abstract: We report on a setup for coherent multidimensional spectroscopy based on visible continuum generation obtained by propagating 130fs, <600µJ pulses centered at 800nm in a 2.5m long hollow-core fibre. We find that with these modest input pulse requirements, the fiber can produce a stable, high brightness continuum spanning the 520nm-900nm region, moreover in a single propagation step. The fibre exhibits 80% transmission and the continuum features excellent spatial mode quality. In addition, spectral phase measurements suggest the possibility of a significantly self-compressed output in the visible, which simplifies aspects of the 2D spectrometer. The applicability of this simple, low requirement, source for 2D spectroscopy is demonstrated by performing a control experiment on the molecular dye Nile Blue.© 2015 Optical Society of America

Radially dependent angular acceleration of twisted light

Carmelo Rosales, Jason Webster, and Andrew Forbes

Doc ID: 283001 Received 16 Dec 2016; Accepted 11 Jan 2017; Posted 13 Jan 2017  View: PDF

Abstract: While photons travel in a straight line at constant velocity in free-space, the intensity profile of structured light may be tailored for acceleration in any degree of freedom. Here we propose a simple approach to control the angular acceleration of light. Using Laguerre-Gaussian modes as our twisted beams carrying orbital angular momentum, we show that superpositions of opposite handedness result in a radially de- pendent angular acceleration as they pass through a focus (waist plane). Due to conservation of orbital angular momentum we find that propagation dynamics are complex despite the free-space medium: the outer part of the beam (rings) rotates in an opposite direction to the inner part (petals), and while the outer part accelerates so the inner part decelerates. We outline the concepts theoretically and confirm them ex- perimentally. Such exotic structured light beams are topical due to their many applications, e.g., optical trapping and tweezing, metrology and fundamental studies in optics.

3 Wavelengths Parallel Phase Shift Interferometry for Real Time Focus Tracking and Vibration Measurement

Michael Ney, Avner Safrani, and Ibrahim Abdulhalim

Doc ID: 282206 Received 06 Dec 2016; Accepted 10 Jan 2017; Posted 18 Jan 2017  View: PDF

Abstract: Instantaneous high resolution, wide range focus tracking and a vibrometry system based on three-wavelength parallel phase shift polarization interferometry using 3 detectors per wavelength is presented. The system, first time implementing 3 wavelengths in parallel three-phase-shift-interferometry channels, allows single shot position tracking of motion profiles with extremely high velocities and vibration rates, long inter-step heights and sub-nm scale accuracy. The system's simple design and algorithm presented here do not rely on active optical components making its performance limited only by the detectors bandwidth and allowing setting up a very high performance low cost vibrometry system.

Tuning of NIR-to-NIR luminescence from one photon to two photons anti-Stokes shift in Ca3Ga2-xCrxGe3O12 via varying Cr3+ content

Gongxun Bai, Huihong Lin, Ting Yu, Qinyuan Zhang, and Jianhua Hao

Doc ID: 283844 Received 30 Dec 2016; Accepted 10 Jan 2017; Posted 17 Jan 2017  View: PDF

Abstract: Near-infrared (NIR) to NIR anti-Stokes luminescence from Cr3+singly-doped Ca3Ga2Ge3O12 (CGGG) occurs under the excitation of 808 nm diode laser. The upconversion (UC) processes vary from one-photon to two-photon, depending on the Cr3+ content (x) in Ca3Ga2-xCrxGe3O12. The results suggest that phonon-assisted anti-Stokes excitation and cooperative energy transfer are involved in the observed UC processes of CGGG: Cr3+. The relevant Cr3+ doping concentration dependent NIR-to-NIR anti-Stokes luminescent mechanism, either one photon or two photons UC is investigated. Such an observation on modulating the UC process via varying the doping concentration, is helpful to broaden the understanding of the UC phenomena.

Shot-noise-limited laser power stabilization for the AEI10m Prototype interferometer

Jonas Junker, Patrick Oppermann, and Benno Willke

Doc ID: 281453 Received 30 Nov 2016; Accepted 10 Jan 2017; Posted 10 Jan 2017  View: PDF

Abstract: The AEI 10m Prototype interferometer is an experimentdesigned to investigate the standard quantumlimit of interferometry and, in particular, its relevancein gravitational wave detection. As such it has stringentrequirements on the power stability of its high-powerlight source.In this paper we present the power stabilization conceptof the 35W Nd:YAG laser system used in theAEI 10m Prototype. With a shot noise limited multiphotodetectorsensing scheme we were able to achievea relative power noise level of 1.8×10^-9 Hz^-1/2 in afrequency band of 100 Hz to 1 kHz. The limiting noisesources at lower and higher frequencies are analyzedand possible improvements on the power noise sensingare discussed. ©

Gamma radiation effects in amorphous silicon and silicon nitride photonic devices

Qingyang Du, Yizhong Huang, Okechukwu Ogbuu, Wei Zhang, Junying Li, Vivek Singh, Anuradha Agarwal, and Juejun Hu

Doc ID: 282830 Received 14 Dec 2016; Accepted 10 Jan 2017; Posted 10 Jan 2017  View: PDF

Abstract: Understanding radiation damage is of significant importance for devices operating in radiation-harsh environments. In this work, we present a systematic study on gamma radiation effects in amorphous silicon and silicon nitride guided wave devices. It is found that gamma radiation increases the material refractive indices by as much as 4 × 10¯³ in amorphous silicon and 4 × 10¯⁴ in silicon nitride at 10 Mrad dose. Our study further reveals that surface oxidation and radiation-induced densification account for the observed index change.

Single-Shot Edge Illumination X-ray Phase-Contrast Tomography Enabled by Joint Image Reconstruction

Mark Anastasio, Yujia Chen, Huifeng Guan, Charlotte Hagen, and A Olivo

Doc ID: 280382 Received 09 Nov 2016; Accepted 10 Jan 2017; Posted 11 Jan 2017  View: PDF

Abstract: Edge illumination X-ray phase-contrast tomography (EIPXCT) is an emerging X-ray phase-contrast tomography technique for reconstructing the complex-valued X-ray refractive index distribution of an object. Conventional image reconstruction approaches for EIXPCT require multiple images to be acquired at each tomographic view angle. This contributes to prolonged data-acquisition times and elevated radiation doses, which can hinder in-vivo applications. In this work, a new 'single-shot' method is proposed for joint reconstruction (JR) of the real and imaginary-valued components of the refractive index distribution from a tomographic data set that contains only a single image acquired at each view angle. The proposed method is predicated upon a non-linear formulation of the inverse problem that is solved by use of a gradient-based optimization method. The method is validated and investigated by use of computer-simulated and experimental EIXPCT data sets.

Minimizing residual spectral drift in laser diode bars using fs-written volume Bragg gratings in fused silica

Daniel Richter, Malte Siems, Maximilian Heck, Thorsten A. Goebel, Christian Matzdorf, Ria Krämer, Andreas Tünnermann, Stefan Nolte, and Wilko Middents

Doc ID: 281845 Received 02 Dec 2016; Accepted 09 Jan 2017; Posted 10 Jan 2017  View: PDF

Abstract: Ultrashort laser pulses are used to inscribe volume Bragg gratings (VBGs) into fused silica. These VBGs demonstrate excellent performance for the external stabilization of laser diode bars. The stabilized system emits at a wavelength of 969nm with a signal width (FWHM) of 100pm and shows a spectral drift as low as 24pm for a change in output power of 45W for a grating surface area of 10mm².

Ultrafast laser mode-locked using Nonlinear Polarization Evolution in Polarization Maintaining fibers

Jan Szczepanek, Tomasz Kardaś, Czeslaw Radzewicz, and Yuriy Stepanenko

Doc ID: 279675 Received 28 Oct 2016; Accepted 09 Jan 2017; Posted 10 Jan 2017  View: PDF

Abstract: In this paper, we demonstrate an all-fiber ultrafast ytterbium laser oscillator mode-locked by means of Nonlinear Polarization Evolution (NPE) method realized in Polarization Maintaining (PM) fibers. A sequence of PM fiber pieces is shown to perform NPE action while maintain a required good temporal overlap of the ordinary and extraordinary pulses propagating through it. We present details of numerical simulations of NPE in PM fibers and compare them to experimental results of the all-PM fiber NPE mode-locked laser cavity. The laser generates ultrashort pulses at 20.54 MHz repetition rate with the dechirped pulse duration around 150 fs and pulse energy of 0.85 nJ.

Narrowband carrier-envelope phase stable mid-infrared pulses at wavelengths beyond 10 µm by chirped-pulse difference frequency generation

Andrea Cartella, tobia nova, Aurelio Oriana, Giulio Cerullo, Michael Foerst, Cristian Manzoni, and Andrea Cavalleri

Doc ID: 280460 Received 08 Nov 2016; Accepted 09 Jan 2017; Posted 10 Jan 2017  View: PDF

Abstract: We report on the generation of narrowband carrier-envelope phase stable mid-infrared (MIR) pulses between 10 and 15 µm. High pulse energies and narrow bandwidths are required for the selective nonlinear excitation of collective modes of matter, not possible with current sources. We demonstrate bandwidths of <2% at 12.5 µm wavelength through difference frequency generation between two near-infrared (NIR) pulses, which are linearly chirped. We obtain a reduction in bandwidth by one order-of-magnitude compared to schemes that make use of transform-limited NIR pulses. The wavelength of the narrowband MIR pulses can be tuned by changing the optical delay between the two chirped NIR pulses.

Upconversion imaging using short-wave infrared picosecond pulses

Morgan Mathez, Peter John Rodrigo, Peter Tidemand-Lichtenberg, and Christian Pedersen

Doc ID: 281201 Received 24 Nov 2016; Accepted 07 Jan 2017; Posted 09 Jan 2017  View: PDF

Abstract: We present the first demonstration of short-wavelength infrared (SWIR) image upconversion that employs intense picosecond signal and pump beams. We use a fiber laser that emits a signal beam at 1877 nm and a pump beam at 1550 nm -- both with pulse width of 1 ps and pulse repetition rate of 21.7 MHz. Due to synchronization of high peak-power pulses, efficient upconversion is achieved in a single-pass setup that employs bulk lithium niobate crystal. Optimizing the temporal overlap of the pulses for high upconversion efficiency enables us to exploit a relatively large pump beam diameter to upconvert a wider range of signal spatial frequencies in the crystal. The 1877 nm signal is converted into 849 nm -- enabling an image to be acquired by a silicon CCD camera. The measured size of the smallest resolvable element of this imaging system is consistent with the value predicted by an improved model that considers the combined image blurring effect due to finite pump beam size, thick nonlinear crystal and polychromatic infrared illumination.

Topological vortex degeneracy lifting and Aharonov-Bohm-like interference in deformed photonic graphene

Zhigang Chen, Daniel Gallardo, Xiang Zhang, Sheng Liu, gao yuanmei, Tongcang Li, Yuan Wang, and Peng Zhang

Doc ID: 279691 Received 03 Nov 2016; Accepted 07 Jan 2017; Posted 12 Jan 2017  View: PDF

Abstract: Photonic graphene, a honeycomb lattice of evanescently coupled waveguides, has provided a superior platform for investigating a host of fundamental phenomena such as unconventional edge states, synthetic magnetic fields, photonic Landau levels, Floquet topological insulators, and pseudospin effects. Here, we demonstrate, both experimentally and numerically, topological vortex degeneracy lifting and Aharonov-Bohm-like interference from local deformation in a photonic honeycomb lattice. When a single valley is excited, lattice deformation leads to generation of a vortex pair due to lifting of degeneracy associated with pseudospin states. In the case of double-valley excitation, we experimentally observe the Aharonov-Bohm-like interference merely due to the deformation of the graphene lattice, which gives rise to an artificial gauge field. Our results may provide insight into the understanding of similar phenomena in two-dimensional graphene-like materials and structures.

Demonstration of km-scale orbital angular momentum (OAM) multiplexing transmission using 4-level pulse-amplitude modulation signals

Long Zhu, Jian Wang, Dequan Xie, and Chen Yang

Doc ID: 282229 Received 07 Dec 2016; Accepted 07 Jan 2017; Posted 13 Jan 2017  View: PDF

Abstract: By designing and fabricating two kinds of orbital angular momentum (OAM) fiber, we demonstrate two OAM modes (OAM+1 and OAM-1) multiplexing transmission and demultiplexing in OAM fiber links. Moreover, we also experimentally demonstrate 4-level pulse-amplitude modulation (PAM-4) signal transmission using two OAM modes multiplexing in km-scale OAM fiber and achieve bit-error rate (BER) below 2x10-3 without multiple-input-multiple-output (MIMO) digital signal processing (DSP). The obtained results with favorable data-carrying OAM multiplexing transmission performance show potential application in km-scale short-reach optical interconnects.

Refractive index and gain grating in Nd:YVO₄: Application to speckle vibrometry and photoacoustic detection.

Baptiste Jayet, Francois Ramaz, and Jean-Pierre Huignard

Doc ID: 281108 Received 30 Nov 2016; Accepted 06 Jan 2017; Posted 13 Jan 2017  View: PDF

Abstract: Probing local displacements on a scattering surface can be achieved using an adaptive interferometer. Photorefractive-crystal based interferometer are popular, but alternatives exist, such as Adaptive Gain interferometer. Such setups take advantage of the non linear phenomena in laser media. Because of the gain saturation, it is possible to write a gain hologram and a refractive index hologram to achieve an adaptive interferometer with a linear response. In addition, laser media based setups have a fast response time (≤ 100 μs), which makes them interesting for application such as detection of photoacoustic waves in living biological samples.

Compensation of the residual linear anisotropy of phase in a VECSEL for spin injection

Alexandre Joly, Ghaya Baili, Mehdi Alouini, Jean-marie George, Isabelle Sagnes, Grégoire Pillet, and Daniel Dolfi

Doc ID: 281323 Received 22 Nov 2016; Accepted 06 Jan 2017; Posted 11 Jan 2017  View: PDF

Abstract: We report the compensation of the linear anisotropy of phase in a VECSEL from 21 to 0.5 mrad with an intracavity PLZT electro-optical ceramic. It allows a dynamic and accurate control of the laser linear anisotropy, as well as a dynamic control of the laser polarization eigenstates. At the birefringence compensation point, we observe an elliptical polarization state with 41° of ellipticity, rotated from its initial position of 32°. The experimental observations are in coherence with the theoretical predictions. Finally, we highlight a control of the polarization state with spin injection.

Compact sorting of optical vortices by means of diffractive transformation optics

Gianluca Ruffato, Michele Massari, and Filippo Romanato

Doc ID: 275364 Received 06 Sep 2016; Accepted 06 Jan 2017; Posted 09 Jan 2017  View: PDF

Abstract: The orbital angular momentum (OAM) of light has recently attracted a growing interest as a new degree of freedom in order to increase the information capacity of today’s optical networks both for free-space and optical fiber transmission. Here we present our work of design, fabrication and optical characterization of diffractive optical elements for compact OAM-mode division demultiplexing based on optical transformations. Samples have been fabricated with 3D high-resolution electron beam lithography on polymethylmethacrylate (PMMA) resist layer spun over a glass substrate. Their high compactness and efficiency make these optical devices promising for integration into next-generation platforms for OAM-modes processing in telecom applications.

Chirp Based Direct Phase Modulation of VCSELs for Cost-Effective Transceivers

Jose A. Altabas, David Izquierdo, Jose Lazaro Villa, and Ignacio Garces

Doc ID: 280562 Received 10 Nov 2016; Accepted 06 Jan 2017; Posted 06 Jan 2017  View: PDF

Abstract: A 2.5Gb/s DPSK transmitter based on direct phase modulation of a VCSEL using its own chirp is proposed. The VCSEL has been characterized both static and dynamically. The sensitivity of a single photodiode heterodyne receiver using the proposed 2.5Gb/s VCSEL transmitter is -39.5dBm, actually an extremely cost-effective transmitter for future access networks

Ultra-compact and temperature-insensitive Mach-Zehnder interferometer based on one multimode waveguide on silicon

Liu Liu, Huizhan Yang, Jianhao Zhang, yuntao zhu, Xuan Zhou, and Sailing He

Doc ID: 281601 Received 29 Nov 2016; Accepted 06 Jan 2017; Posted 06 Jan 2017  View: PDF

Abstract: An ultra-compact and temperature-insensitive Mach-Zehnder interferometer device is introduced on the silicon-on-insulator platform. The device is constructed through one straight multimode waveguide, which consists of two densely packed silicon wires with a narrow gap of varying positions along the device. The total width of the proposed Mach-Zehnder interferometer is only about 1μm. Interference patterns with extinction ratios of better than 20dB are achieved. Temperature insensitive operation of the proposed device is also demonstrated for both global and local temperature changes. The shift rate of the wavelength response with respect to the substrate temperature change is within ±10pm/K in 30-nm wavelength range.

Generation of ultra-wideband achromatic Airy plasmons on graphene surface

Chunying Guan, Gilberto Brambilla, Jin-hui Shi, Tingting yuan, rang chu, yize Shen, Libo Yuan, zheng zhu, and Ping Li

Doc ID: 281686 Received 29 Nov 2016; Accepted 05 Jan 2017; Posted 09 Jan 2017  View: PDF

Abstract: Tunable ultra-wideband achromatic plasmonic Airy beams are demonstrated on graphene surfaces. Surface plasmonic polaritons are excited using diffractive gratings. The phase and amplitude of plasmonic waves on the graphene surface are determined by the relative position between the grating arrays and duty ratio of the grating unit cell, respectively. The transverse acceleration and nondiffraction properties of plasmonic waves are observed. The achromatic Airy plasmons with identical acceleration trajectory at different excited wavelengths can be achieved by tuning dynamically the Fermi energy of graphene without reoptimizing the grating structures. The proposed devices may find applications in photonics integrations and surface optical manipulation.

Soliton-mediated orientational ordering of gold nanorods and birefrigence in plasmonic suspensions

Yuxuan Ren, Trevor Kelly, Chensong Zhang, Huizhong Xu, and Zhigang Chen

Doc ID: 281862 Received 30 Nov 2016; Accepted 05 Jan 2017; Posted 11 Jan 2017  View: PDF

Abstract: We report on soliton-mediated orientational ordering of gold nanorods in a colloidal plasmonic suspension. Due to nonlinear optical response of the suspension, a light beam forms an optical spatial soliton which creates an effective optical waveguide. The orientation of the nanorods along the waveguide is regulated by the optical torque exerted by the linearly polarized soliton beam. By measuring the polarization transmission spectrum of a probe beam at a wavelength far away from the plasmonic resonance, we observe orientation-enhanced birefringence along the soliton channel, suggesting a disorder-to-order transition of nanorods due to the action of the soliton beam. This approach may be applied in other colloidal systems with optical force-induced nonlinearity.

Two-photon polymerization of microstructures by non-diffraction multifoci pattern generated from superposed Bessel beam

Liang Yang, DongDong Qian, Chen Xin, Zhijiang Hu, Shengyun Ji, Dong Wu, Yanlei Hu, Jiawen Li, wenhao huang, and Jiaru Chu

Doc ID: 282756 Received 13 Dec 2016; Accepted 05 Jan 2017; Posted 17 Jan 2017  View: PDF

Abstract: In this paper, superposed Bessel beams (SBBs) are realized by alternatively imprinting holograms of opposite order Bessel beams along the radial direction on a spatial light modulator (SLM). The propagation invariance and nonrotation properties of SBBs are theoretically predicted and experimentally demonstrated. The focusing property of SBBs with high numerical aperture (NA) objective is investigated with Debye vectorial diffraction theory. Near the focal plane, circularly distributed multiple foci pattern is achieved. The multiple foci generated from SBBs are adopted in a two-photon fabrication system and micropattern fabrication by a single exposure is demonstrated. Facile fabrication of three dimensional microstructures with SBBs is realized by dynamically controlling the number of focal spots, the diameter and rotation of focal pattern.

Higher-Order Laguerre-Gauss Modes in (Non-) Planar Four-Mirror Cavities for Future Gravitational Wave Detectors

Andreas Noack, Christina Bogan, and Benno Willke

Doc ID: 279455 Received 30 Nov 2016; Accepted 04 Jan 2017; Posted 09 Jan 2017  View: PDF

Abstract: One of the limiting noise sources in the current generation of gravitational wave detectors, such as the advanced Laser Interferometer Gravitational wave Observatory (aLIGO), is the thermal noise in the interferometer's test mass coatings. One proposed method to reduce the coupling of this noise source to the gravitational wave readout is using a laser beam in the higher-order spatial LG$_{33}$ mode within the interferomter.Here, we show that the current four-mirror cavities of aLIGO are not compatible with Laguerre-Gauss modes due to astigmatism. A \textit{non-degeneracy} of modes of the same order could be observed in experiment and simulation. We demonstrate that a non-planar cavity could be used instead as it compensates the astigmatism and transmitts the LG$_{33}$ mode undisturbed.

Control of dissipative solitons in a magneto-optic planar waveguide

Vladimir Tuz, Bogdan Kochetov, Iaroslavna Vasylieva, Lyudmila Kochetova, and Hong-Bo Sun

Doc ID: 281806 Received 29 Nov 2016; Accepted 03 Jan 2017; Posted 05 Jan 2017  View: PDF

Abstract: We propose a mechanism to control propagation of a group of stable dissipative solitons in a nonlinear magneto-optic planar waveguide. The control is realized by means of a spatially inhomogeneous external magnetic field which is induced by a set of direct conducting wires placed on the top of the guiding layer. The wires are extended in the direction of soliton propagation, and carry electric currents with particular piecewise constant profiles. In order to describe the soliton evolution the one-dimensional cubic-quintic complex Ginzburg–Landau equation has been adapted by tailoring an additional linear term, which is responsible for the magneto-optic effect.

Broadband atomic-layer MoS2 optical modulators for ultrafast pulse generations in the visible range

Haohai Yu, Yuxia Zhang, Rui Zhang, Gang Zhao, Huaijin Zhang, Yanxue Chen, Liangmo Mei, Mauro Tonelli, and Jiyang Wang

Doc ID: 282101 Received 07 Dec 2016; Accepted 02 Jan 2017; Posted 05 Jan 2017  View: PDF

Abstract: Visible lasers are a fascinating regime and their significance is illustrated by the 2014 Noble prizes in physics and chemistry which are awarded for the progress in the invention and applications of visible lasers, respectively. With the development of blue laser-diodes, the laser-diode pumped solid-state visible lasers become a burgeoning direction nowadays. Constrained by the scarce visible optical modulators, the solid-state ultrafast visible lasers are few realized. Based on the bandgap structure and optoelectronic properties of atomic-layer MoS2, it can be proposed that it has potentials as visible optical modulators. Here, by originally revealing layer-dependent nonlinear absorption of atomic-layer MoS2 in the visible range, broadband atomic-layered MoS2 optical modulators for the visible ultrafast pulse generation are developed and selected based on the proposed designing criterion for novel two-dimensional optical modulators. By applying the selected MoS2 optical modulators in the solid-state praseodymium lasers, broadband mode-locked ultrafast lasers from 522 to 639 nm are originally realized. We believe that this work should promote the development of visible ultrafast photonics and further applications of two-dimensional optoelectronic materials.

Mid-infrared wavelength conversion from As₂Se₃ microwires

lizhu Li, Nurmemet Abdukerim, and Martin Rochette

Doc ID: 280730 Received 17 Nov 2016; Accepted 02 Jan 2017; Posted 05 Jan 2017  View: PDF

Abstract: We demonstrate all-fiber far-detuned and widely tunable mid-infrared wavelength conversion using As₂Se₃ microwires. In a first experiment, an idler is generated and tuned from 2.351 μm to >2.500 μm from four-wave mixing in a 0.5 cm long microwire. In a second experiment, tunable parametric sidebands are generated via modulation instability in a 10 cm long microwire. The resulting parametric frequency conversion reaches up to 49.3 THz, the largest ever reported in soft glass materials.

Saturated two-photon excitation fluorescence microscopy with core-ring illumination

Katsumasa Fujita, Atsushi Doi, Nicholas Smith, Ryosuke Oketani, Yasunori Nawa, and Satoshi Kawata

Doc ID: 281460 Received 28 Nov 2016; Accepted 31 Dec 2016; Posted 09 Jan 2017  View: PDF

Abstract: We demonstrated resolution improvement in two-photon excitation microscopy by combining saturated excitation of fluorescence and pupil manipulation. We theoretically estimated the resolution improvement and the sidelobe effect in the point spread function with various pupil designs and found that the combination of saturated excitation and core-ring illumination can effectively enhance the spatial resolution in 3D and suppress sidelobe artifacts. The experimental demonstration shows that the proposed technique is effective for observation with a depth of 100 µm in a tissue phantom and can be applied to 3D observations of tissue samples with higher spatial resolution than conventional two-photon excitation microscopy.

GaInP on Oxide Nonlinear Photonic Crystal Technology

Aude Martin, Dorian Sanchez, Sylvain Combrié, Alfredo De Rossi, and Fabrice Raineri

Doc ID: 279577 Received 14 Dec 2016; Accepted 30 Dec 2016; Posted 10 Jan 2017  View: PDF

Abstract: Heat dissipation is optimized in nonlinear III-V photonic crystal waveguides owing to the hybrid IIIV/Silicon integration platform, allowing efficient Four-Wave-Mixing in the continuous wave regime. In dispersion-engineered waveguides with flat group index of 28 over a 10 nm bandwidth, the conversion efficiency is -17.6 dB with a pump power level below 100 mW.

Enhancement of third order nonlinear optical susceptibility of Alq3 in polar aprotic solvents

Beata Derkowska

Doc ID: 283088 Received 21 Dec 2016; Accepted 30 Dec 2016; Posted 03 Jan 2017  View: PDF

Abstract: The influence of solvent polarity on nonlinear optical properties of tris-(8-hydroxyqinoline)-aluminum (Alq3) was investigated by degenerate four wave mixing (DFWM) method at the 532 nm. It was obtained that the effective values of the third order nonlinear optical susceptibility (chi<3> ) and the second order hyperpolarizability (gamma) of Alq3 depends on the solvent polarity. Additionally, it was found that Alq3 dissolved in DMSO has the highest values of chi<3> and gamma . Furthermore, two Stegemen’s figures of merit were also calculated. The obtained results suggest that Alq3 is very promising material also for application in all-optical signal processing devices.

Fabrication of anti-reflective microstructure on sapphire by femtosecond laser direct writing

Qi-Dai Chen, Qian-Kun Li, Jiaji Cao, yanhao yu, Lei Wang, Yun-Lu Sun, and Hong-Bo Sun

Doc ID: 281936 Received 01 Dec 2016; Accepted 29 Dec 2016; Posted 03 Jan 2017  View: PDF

Abstract: Herein, we report a facile approach for maskless production of subwavelength structured antireflective surfaces on sapphire with high and broadband transmittance in Mid-IR—femtosecond laser direct writing assist with wet etching. With this method, inverted pyramid and cone arrays with a pitch of about 2 μm and a total height of near 900 nm on sapphire were produced. The resulting subwavelength structures greatly suppress specular reflection at normal incidence. Transmission measurements between 3 μm and 5 μm are in agreement with simulations using VirtualLab, the transmittance reached a maximum value of 92.5% at 4 μm. Besides, the sapphire with subwavelength structures also exhibits angle-independent transmittance characteristics up to a high θ=60°. Therefore, these subwavelength structures on sapphire are of great technological importance in Mid-IR optics especially for harsh-condition-applicable windows of military Mid-IR devices.

Dual-pump generation of high-coherence primary Kerr combs with multiple sub-lines

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

Doc ID: 281642 Received 28 Nov 2016; Accepted 28 Dec 2016; Posted 06 Jan 2017  View: PDF

Abstract: We experimentally generate high-coherence primary Kerr combs with multiple sub-lines by using dual pumps and demonstrate such high coherence in multichannel communications. We find that more than 10 primary comb lines can be generated within the spectrum of modulation instability gain in our microring resonator. The generation is also verified by numerical simulations and the measured linewidth confirms the high coherence of the generated primary comb lines. We also demonstrate the high-coherence characteristics in a coherent communication experiment, in which each comb line is encoded with 20 Gbaud quadrature phase-shift-keyed signals. Moreover, it is experimentally observed that pump phase difference has no effect on primary comb generation.

Segmented waveguide arrays: deriving discrete diffraction relations in a square lattice photonic crystal

Nadia Belabas, Christophe Minot, Jean-Marie Moison, Stephane Guilet, Edmond Cambril, and J. Ariel Levenson

Doc ID: 277938 Received 05 Dec 2016; Accepted 27 Dec 2016; Posted 03 Jan 2017  View: PDF

Abstract: Segmented strip-loaded waveguide arrays are investigated within a rigorous square lattice photonic crystal model. We derive a full multiband discrete diffraction approach for near-axial injection in the direction of a lattice vector. We obtain an effective waveguide array picture, with quasi-linear dependence on the segmentation ratio in a simplified single-band scheme. Our results are validated by beam deviation experiments. Such a diffraction framework allows for efficient shaping of the phase map in waveguide arrays and enriches the engineering tool kit of photonic crystals with the in-plane free propagation structures of discrete photonics.

Photoacoustic resonance by spatial filtering of focused ultrasound transducers

Dongyel Kang, Bahman Lashkari, and Andreas Mandelis

Doc ID: 281791 Received 01 Dec 2016; Accepted 27 Dec 2016; Posted 11 Jan 2017  View: PDF

Abstract: The effect of a spherically focused ultrasound (US) transducer (TD) on photoacoustic (PA) measurements is analytically investigated using the concept of a virtual point detector. The derived analytical results indicate that the limited numerical aperture (NA) of the PA detector takes on the role of spatial filtering of the induced PA waves, which leads to the occurrence of a peak frequency in the PA spectrum. The mathematical description of this phenomenon is similar to the result of resonance peaks of light propagation in dielectrics. This PA resonance peak depends on the NA of the US TD and the absorption coefficient of the PA source. Experimentally measured PA spectra from an ink solution using a frequency-domain PA system verify the PA resonance effect. Finally, we discuss the possibility that previously reported PA resonances interpreted as PA source viscosity might be actually caused by the US TD’s spatial filtering.

Wavefront sensing based on spatial light modulator and four-step incremental binary random sampling

Cheng-Shan Guo, Ben-Yi Wang, Lu Han, Yang Yang, and Qing-Yang Yue

Doc ID: 278603 Received 12 Oct 2016; Accepted 26 Dec 2016; Posted 11 Jan 2017  View: PDF

Abstract: A wavefront sensing method based on a spatial light modulator (SLM) and a four-step incremental binary random sampling (IBRS) algorithm is proposed. In this method, the recording setup is built just by a transmittance SLM and an image sensor. The tested wavefront incident to the SLM plane can be quantitatively retrieved from four diffraction intensities of the wavefront passed through the SLM displaying a IBRS pattern. Because only two modulation states (opaque and transparent) of the SLM are used, it does not need to know the concrete modulation function of the SLM in advance. And by introducing the concept of the incremental random sampling into wavefront sensing, the adaptability of phase retrieving based on the diffraction intensities are significantly improved. To the best of our knowledge, no previous study has used this concept for the purpose. Some experimental results are given for demonstrating the feasibility of the method.

Emission properties of second-harmonic generation in AlGaAs optical nanoantennas

Michele Celebrano, Lavinia Ghirardini, Luca Carletti, Valerio Gili, Giovanni Pellegrini, Lamberto Duò, Marco Finazzi, Davide Rocco, Andrea Locatelli, Costantino De Angelis, Ivan Favero, Giuseppe Leo, Marco Ravaro, and Aristide Lemaître

Doc ID: 281537 Received 25 Nov 2016; Accepted 25 Dec 2016; Posted 05 Jan 2017  View: PDF

Abstract: Manipulating light at the nanoscale by means of dielectric nanoantennas has recently received renewed attention thanks to the development of key-enabling fabrication tools in semiconductor technology, which effectively add-up to the low losses exhibited by dielectrics in the optical regime compared to metals. Nanostructures based on III-V type semiconductors, characterized by an intrinsic broken symmetry down to the single elementary cell, recently demonstrated unique nonlinear optical properties confined at scales well below the operating wavelength. In this letter, we investigate the emission properties of the second harmonic generation (SHG) in AlGaAs monolithic nanoantennas. Our findings point towards the pivotal role of the volume susceptibility in the SHG emission, hence bringing further insight in the mechanism underlying the nonlinear processes occurring in these systems. The unprecedented SHG efficiency attained together with the control over the polarized emission from these nanoantennas constitutes a key ingredient for the future development of nonlinear metasurfaces with tunable emission properties.

Electrically tunable coalescence of exceptional points in parity-time symmetric waveguides

Kin Hung Fung, Raymond P.H. Wu, Hui Yuan Dong, J. Wang, and T. C. Mok

Doc ID: 277544 Received 03 Oct 2016; Accepted 24 Dec 2016; Posted 03 Jan 2017  View: PDF

Abstract: We demonstrate theoretically the high electric tunability of the emergence and coalescence of exceptional points in PT-symmetric waveguides bounded by imperfect conductive layers. Owing to the competition effect of multimode interaction, multiple exceptional points and PT phase transitions could be attained in such a simple system and, meanwhile, their occurrences are strongly dependent on the boundary conductive layers. When the conductive layers become very thin, it is found that the sideway transmittance and reflectance of the same system can be tuned between zero and one by a small change in carrier density. The results may provide an effective method for fast tuning and modulation of optical signals through electrical gating.

Strip-loaded waveguide on titanium dioxide thin films by nanoimprint replication

Leila Ahmadi, Ville Kontturi, Janne Laukkanen, Jyrki Saarinen, Seppo Honkanen, Markku Kuittinen, and Matthieu Roussey

Doc ID: 278355 Received 11 Oct 2016; Accepted 23 Dec 2016; Posted 03 Jan 2017  View: PDF

Abstract: We present a convenient low cost and mass-production compatible technique for the fabrication of strip-loaded waveguides. The technique is based on the atomic layer deposition of a slab waveguide, nanoimprinting of a strip and integration of two structures by lamination. The guiding layer is chosen to be a 200 nm-thick titanium dioxide film. The waveguide characteristics are determined by the use of ring resonators. The technique is demonstrated for titanium dioxide thin films but it is applicable to any other material which meets the refractive index difference condition between the loading strip and the slab waveguide.

Topological events on lines of circular polarization in nonparaxial vector optical fields

Isaac Freund

Doc ID: 280835 Received 15 Nov 2016; Accepted 18 Dec 2016; Posted 09 Jan 2017  View: PDF

Abstract: In nonparaxial vector optical fields the following topological events areshown to occur in apparent violation of charge conservation: as one translates the observation plane along a line of circular polarization (a C line), points on the line (C points) are seen to change not only the signs of their topological charges, but also their handedness, and, at turning points on the line, paired C points with the same topological charge and opposite handedness are seen to nucleate. These counter-intuitive events cannot occur in paraxial fields.

Reflectance-mode iNIRS (interferometric near-infrared spectroscopy) quantifies brain absorption, scattering, and blood flow index in vivo

Dawid Borycki, Oybek Kholiqov, and Vivek Srinivasan

Doc ID: 282266 Received 06 Dec 2016; Accepted 16 Dec 2016; Posted 03 Jan 2017  View: PDF

Abstract: Interferometric near-infrared spectroscopy (iNIRS) is a new technique that measures time-of-flight- (TOF-) resolved autocorrelations in turbid media, enabling simultaneous estimation of optical and dynamical properties. Here, we demonstrate reflectance-mode iNIRS for non-invasive monitoring of the mouse brain in vivo. A method for more precise quantification with less static interference from superficial layers, based on separating static and dynamic components of the optical field autocorrelation, is presented. Absolute values of absorption, reduced scattering, and blood flow index (BFI) are measured and changes in BFI and absorption are monitored during a hypercapnic challenge. Absorption changes from TOF-resolved iNIRS are compared with absorption changes from continuous wave (CW) NIRS analysis, based on TOF-integrated light intensity changes, an effective path length, and the Modified Beer-Lambert Law. Thus, iNIRS is a promising approach for quantitative and non-invasive monitoring of perfusion and optical properties in~vivo

InP Photonic Integrated Externally Injected Gain Switched Optical Frequency Comb

Maria Deseada Gutierrez Pascual, Vidak Vujicic, Jules Braddell, Frank Smyth, Prince Anandarajah, and Liam Barry

Doc ID: 279569 Received 27 Oct 2016; Accepted 13 Dec 2016; Posted 14 Dec 2016  View: PDF

Abstract: We report on an InP photonic integrated circuit for the generation of an externally injected gain switched optical frequency comb. The device is fully characterized and generates a comb with frequency spacing ranging from 6-10 GHz, good noise properties that include relative intensity noise of <-130 dB/Hz and linewidth of 1.5 MHz, and high phase correlation between comb lines. These characteristics, in conjunction with the compactness and cost efficiency of the integrated device, demonstrate the quality of the resultant comb source for numerous applications.

Dynamic particle enhancement in limited-view optoacoustic tomography

Xose Luis Dean Ben, Lu Ding, and Daniel Razansky

Doc ID: 276271 Received 27 Sep 2016; Accepted 06 Dec 2016; Posted 17 Jan 2017  View: PDF

Abstract: Limited-view artefacts are commonly present in optoacoustic tomography images, mainly due to practical geometrical and physical constraints imposed by the imaging systems as well as limited light penetration into large optically opaque samples. Herein, a new approach termed dynamic particle-enhanced optoacoustic tomography (DPOT) is proposed for improving image contrast and visibility of optoacoustic images under limited-view scenarios. The method is based on the non-linear combination of a temporal sequence of tomographic reconstructions representing sparsely distributed moving particles. We demonstrate experimental performance by dynamically imaging the flow of suspended microspheres in three dimensions, which shows promise for DPOT applicability in angiographic imaging in living organisms.

Simultaneous Two-color Stimulated Raman Scattering Microscopy by Adding a Fiber Amplifier to a 2 Picosecond OPO Based SRS Microscope

Wenlong Yang, Ang Li, yuanzhen suo, Fa-Ke Lu, and Xiaoliang Xie

Doc ID: 276465 Received 26 Oct 2016; Accepted 02 Dec 2016; Posted 21 Dec 2016  View: PDF

Abstract: Stimulated Raman scattering (SRS) microscopy is a label-free chemical imaging technique. Two-color imaging is necessary to confirm chemical distribution in SRS microscopy. Current multi-color SRS always requires complicated instrumentation or has other limitations. We showed that by adding a simple fiber amplifier to a 2-ps laser source and optical parametric oscillator based SRS setup, one can achieve simultaneous two-color and frequency modulation SRS microscopy. The fiber amplifier can generate wavelength tunable laser ±10 nm around the Stokes laser wavelength with average power higher than 200 mW. In vivo and ex vivo lipid-protein imaging of mice brain and skin are demonstrated. To further demonstrate the potential of this technique in high-speed in vivo imaging, white blood cells in blood stream were imaged in live mice.

High-extinction ratio integrated photonic filters for silicon quantum photonics

Mateusz Piekarek, Damien Bonneau, Shigehito Miki, Taro Yamashita, Mikio Fujiwara, Masahide Sasaki, H Terai, Michael Tanner, Robert Hadfield, Chandra Natarajan, Jeremy O'Brien, and Mark Thompson

Doc ID: 269910 Received 06 Oct 2016; Accepted 29 Nov 2016; Posted 01 Dec 2016  View: PDF

Abstract: We present the generation of quantum-correlated photon pairs and subsequent pump rejection across two silicon-on-insulator photonic integrated circuits. Incoherently cascaded lattice filters are used to provide over 100 dB pass-band to stop-band contrast with no additional external filtering. Photon pairs generated in a microring resonator are successfully separated from the input pump, confirmed by a temporal correlations measurements.

New approach for power scaling solid-state lasers with intracavity motion

W. Clarkson, Matthew Eckold, and Jacob Mackenzie

Doc ID: 278680 Received 14 Oct 2016; Accepted 23 Nov 2016; Posted 28 Nov 2016  View: PDF

Abstract: Solid-state lasers are typically limited by adverse thermal effects within the gain medium. In this paper we describe a new method for dramatically reducing thermal effects in an end-pumped solid-state laser by incorporating a rotating intracavity periscope in the resonator to spatially separate the lasing and thermal processes. In contrast to previous examples of moving solid-state lasers our approach keeps the gain medium stationary simplifying the heat removal arrangement. This scheme has been applied to a Nd:YAG laser yielding an output power of 120 W at 1.064 μm, limited by available pump power. Analysis suggests that scaling to much higher power is feasible with the appropriate laser design.

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