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Accepted papers to appear in an upcoming issue

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All-optical flip-flop based on hybrid square-rectangular bistable lasers

Yong-Zhen Huang, Xiu-Wen Ma, Yue-De Yang, Hai-Zhong Weng, Fu-Li Wang, Min Tang, Jin-Long Xiao, and Yun Du

Doc ID: 292520 Received 12 Apr 2017; Accepted 21 May 2017; Posted 23 May 2017  View: PDF

Abstract: A compact, simple, and bistable hybrid square-rectangular laser is experimentally demonstrated as an all-optical flip-flop memory. Controllable bistability is induced by two-mode competition together with the saturable absorption at the square microcavity section. The all-optical set and reset operations are realized by injecting signal pulses at two mode wavelengths, with the response times of 165 and 60 ps at the triggering pulse width of 100 ps and switching energies of 2.7 fJ and 14.2 fJ, respectively. The robust hybrid-cavity design has an active area of 660 μm2 and permits efficient unidirectional single-mode lasing, low-power flip-flop operation, and superior fabrication tolerance for monolithic photonic integration.

Controlled Non-Canonical Vortices from Higher Order Fractional Screw Dislocations

Maruthi Brundavanam and Satyajit Maji

Doc ID: 294779 Received 27 Apr 2017; Accepted 21 May 2017; Posted 23 May 2017  View: PDF

Abstract: A pair of stable non-canonical vortices of same charge is generated experimentally across the cross-section of an optical beam using computer generated hologram with higher order fractional screw dislocation. Non-canonical nature of the generated vortices is identified by the gradient of phase around each vortex and also the crossing angle between the zero contours of the real and imaginary parts of the optical field. The anisotropy of the vortices can be controlled by the fractional order of the computer generated hologram. The behavior of the rate of change of phase around each individual vortex is found to be different from the earlier reports on non-canonical vortices. The observed experimental results are qualitatively explained based on the effect of non-localized phases of the generated vortices. The generated beams with nested pair of non-canonical vortices can be of importance in accelerated rotation of the beams and in optical micro-manipulation.

15.2 W spectrally-flat all-fiber supercontinuum laser source with >1 W power beyond 3.8 μm

Jing Hou, Ke Yin, Linyong Yang, and Bin Zhang

Doc ID: 294903 Received 28 Apr 2017; Accepted 20 May 2017; Posted 23 May 2017  View: PDF

Abstract: In this letter, a high-power 1.9-4.2 μm supercontinuum (SC) laser source with a real all-fiber structure is reported. A 12 m length of ZBLAN fluoride fiber was used as the nonlinear medium, which was pumped by a thulium-doped fiber amplifier (TDFA) through a firm fusion-spliced joint between silica fiber and itself. The obtained SC laser had a high-spectral-flatness with a maximal 10 dB bandwidth of 2090 nm spanning from 1960 to 4050 nm. A record SC power of 15.2 W for all-fiber mid-infrared SC laser was measured, while the SC power beyond 3.0 and 3.8 μm was 8.1 and 1.08 W which were both the highest average power in a fiber laser, corresponding to a power ratio of 53.2 % and 7.1 % respectively. The average spectral power density of this SC laser was as high as 7.2 mW/nm. This work, to the best of our knowledge, represents the brightest all-fiber mid-infrared SC laser, and also provides a promising high-power pump light for SC generation in cascaded chalcogenide fibers.

Field-induced lifetime prolonging effect of photorefractive grating in Mn:Fe:KTN crystal

Lu Qieni, Bihua Li, Zhen Li, and Baozhen Ge

Doc ID: 292688 Received 13 Apr 2017; Accepted 19 May 2017; Posted 19 May 2017  View: PDF

Abstract: In this letter, we report the lifetime prolonging effect of light-induced refractive index grating by applied bias electric field. The dynamic behavior of photorefractive grating dark decay in Mn:Fe:KTN crystal is visualized and monitored in situ by means of digital holographic microscopy. Subsequently, the dark decay time of phase grating can be achieved according to the dynamic behavior, and is longer with higher electric field applied during writing. The lifetime prolonging of grating is attributed to polar nanoregions induced by external field. This effect can be of interest for many relevant applications, such as electroholographic switching.

Optical microscope illumination analysis using through-focus scanning optical microscopy

Ravikiran Attota and Haesung Park

Doc ID: 290826 Received 16 Mar 2017; Accepted 19 May 2017; Posted 23 May 2017  View: PDF

Abstract: Misalignment of the aperture diaphragm present in optical microscopes results in angular illumination asymmetry (ANILAS) at the sample plane. Here we show that through-focus propagation of ANILAS results in lateral image shift with focus position. This could lead to substantial errors in quantitative results for optical methods that use through-focus images such as three-dimensional nanoparticle tracking, confocal microscopy, and through-focus scanning optical microscopy (TSOM). A correlation exists between ANILAS and the slant in TSOM images. Hence, the slant in the TSOM image could be used to detect, analyze and rectify the presence of ANILAS.

1-GHz InP On-chip Monolithic Extended Cavity Colliding-Pulse Mode-Locked Laser

Robinson Guzman, Guillermo Carpintero, Carlos Gordon, and Luis Orbe

Doc ID: 292139 Received 04 Apr 2017; Accepted 19 May 2017; Posted 23 May 2017  View: PDF

Abstract: Record low repetition rate from an on-chip monolithic InP extended cavity colliding-pulse mode-locked laser is experimentally reported. The device, fabricated in generic InP based active-passive integration technology, makes use of integrated mirrors to enable its use as a building block within a photonic integrated circuit. This structure allows us to generate an electrical frequency comb with mode spacing of 1 GHz, determined by the 40.5 mm long resonator. Passive and hybrid mode-locking regimes conditions are experimentally demostrated. In the passive regime, an electrical beat tone at the fundamental repetition rate with an electrical linewidth of 398 kHz and signal-to-noise ratio > 30 dB is measured. In the hybrid regime, the optical comb is locked to a continuous wave signal source, improving the generated signal to an electrical linewidth less than 1 Hz and signal-to-noise ratio > 40 dB

Low-loss and low-crosstalk multi-channel mode (de)multiplexer based on ultrathin silicon nanowire waveguides

Chenlei Li and Daoxin Dai

Doc ID: 295782 Received 10 May 2017; Accepted 18 May 2017; Posted 23 May 2017  View: PDF

Abstract: A multi-channel mode (de)multiplexer based on the super-mode evolution in cascaded dual-core adiabatic tapers is designed and realized with ultrathin (~50nm) silicon-on-insulator nanowire waveguides. This dual-core adiabatic taper is designed optimally, so that all the supermodes are confined in the wide core at the input end and the highest-order supermode is localized in the narrow core at the output end. In this way, the highest-order supermode is dropped as the fundamental mode at the cross port. As an example, a (de)multiplexer with three mode-channels is designed and fabricated. From the measured spectral responses, the fabricated device has a crosstalk lower than −20dB and an excess loss less than 0.2dB in a bandwidth of ~65nm.

Optical solver for system of ordinary differential equations based on external feedback assisted microring resonator

Xinliang Zhang, Jie Hou, and Jianji Dong

Doc ID: 293086 Received 19 Apr 2017; Accepted 17 May 2017; Posted 19 May 2017  View: PDF

Abstract: Systems of ordinary differential equations (SODEs) are crucial for describing the dynamic behaviors in various systems, such as the modern control systems which requires observability and controllability. In this paper, we propose and experimentally demonstrate an all-optical SODE solver based on the silicon-on-insulator (SOI) platform. We use an add/drop microring resonator to construct two different ordinary differential equations (ODEs) and then introduce two external feedback waveguides to realize the coupling between these ODEs, thus forming the SODE solver. Temporal coupled mode theory (CMT) is used to deduce the expression of the SODE. A system experiment is carried out for further demonstration. For the input 10 Gb/s NRZ-like pulses, the measured output waveforms of the SODE solver agree well with the calculated results.

A precise determination on the upconversion processes of the ultraviolet upconversion fluorescence of Ho3+-doped Y2O3 ceramic by excitation of a 532-nm continues-wave laser

feng qin, Hua Zhao, Moyang Lv, Leipeng Li, Yuan Zhou, zhengjia wang, Yangdong Zheng, Zhiguo Zhang, and wenwu cao

Doc ID: 294572 Received 28 Apr 2017; Accepted 17 May 2017; Posted 17 May 2017  View: PDF

Abstract: Aiming at developing the Ho3+–based continues–wave ultraviolet laser, the method determining the weight of the excited–state absorption (ESA) process occupied in the populating of the 3D3 level is studied. By way of rate equations model, the weight is found to be related with the weighting factors of the double-exponential decay components of the 3D3 level. Experimentally, utilizing time-resolved spectroscopy, the weight of ESA process for Y2O3 ceramic doped with 0.1 mol % Ho3+ is determined to be 83%. Further, the fluorescence dynamic properties of the Ho3+-doped Y2O3 ceramic with different doping concentrations were analyzed, and the weight is found to be decreased with doping concentration but no less than 70%.

Nondiffracting self-imaging of ultrashort wavepackets

Alexander Treffer, Ruediger Grunwald, and Martin Bock

Doc ID: 287351 Received 27 Feb 2017; Accepted 17 May 2017; Posted 19 May 2017  View: PDF

Abstract: Self-imaging of ultrashort-pulsed nondiffracting needle beams, i.e. fringe-free Bessel beams, is analyzed. In contrast to the classical diffractive Talbot effect, pulse revivals with minimum spectral and temporal distortion are obtained. Robustness is further enhanced by self-reconstruction. The high-fidelity pulse transfer enables for spatial and temporal multiplexing in free space without the need for a nonlinear medium even at pulse durations down to the few-cycle range.

Self-referenced frequency combs using high-efficiency silicon-nitride waveguides

David Carlson, Daniel Hickstein, Alexander Lind, Stefan Droste, Daron Westly, Nima Nader, Ian Coddington, Nathan Newbury, Kartik Srinivasan, Scott Diddams, and Scott Papp

Doc ID: 292633 Received 13 Apr 2017; Accepted 17 May 2017; Posted 19 May 2017  View: PDF

Abstract: We utilize silicon-nitride waveguides to self-reference a telecom-wavelengthfiber frequency comb through supercontinuum generation, using 11.3 mW of optical power incident on the chip. This is approximately ten times lower than conventional approaches using nonlinear fibers and is enabled by low-loss (<2 dB) input coupling and the high nonlinearity of silicon nitride, which can provide two octaves of spectral broadening with incident energies of only 110 pJ. Following supercontinuum generation, self-referencing is accomplished by mixing 780-nm dispersive-wave light with the frequency-doubled output of the fiber laser. In addition, at higher optical powers, we demonstrate f-to-3f self-referencing directly from the waveguide output by the interference of simultaneous supercontinuum and third harmonic generation, without the use of an external doubling crystal or interferometer. These hybrid comb systems combine the performance of fiber-laser frequency combs with the high nonlinearity and compactness of photonic waveguides, and should lead to low-cost, fully stabilized frequency combs for portable and space-borne applications.

Ergodic and non-ergodic regimes in temporal laser speckle imaging

Pavel Zakharov

Doc ID: 290924 Received 21 Mar 2017; Accepted 16 May 2017; Posted 17 May 2017  View: PDF

Abstract: The non-ergodicity problem of temporal averaging in the laser speckle imaging (LSI) is discussed both theoretically and numerically. We demonstrate that temporal speckle statistics assessed within finite time window might differ from the statistics of the speckle ensemble. The dependence of temporal speckle contrast on sample dynamics is non-monotonic and demonstrates regimes of negative (ergodic) as well as positive correlations with dynamics (non-ergodic). The ergodic regime is similar to ensemble (spatial) averaging case and is typically assumed for interpretation of LSI measurements. The positive relation in non-ergodic regime is an artefact of temporal statistics which we further quantify and describe transition between two regimes.

Aliasing, coherence and resolution in a lensless holographic microscope

Temitope Agbana, Hai Gong, Gleb Vdovin, Michel Verhaegen, Vitalii Bezzubik, and Abena Amoah

Doc ID: 292435 Received 07 Apr 2017; Accepted 15 May 2017; Posted 19 May 2017  View: PDF

Abstract: We have shown that the maximum achievable resolution of in-line lensless holographic microscope is limited by aliasing and, for collimated illumination, can not exceed the camera pixel size. This limit can be achieved only when the optimal conditions on spatial and temporal coherence state of the illumination are satisfied. The expressions defining the configuration, delivering maximum resolution with given spatial and temporal coherence of the illumination are obtained. The validity of these conditions is confirmed experimentally.

Sellmeier equations, group velocity dispersion and thermo-optic dispersion formulas for CaLnAlO4 (Ln = Y, Gd) laser host crystals

Pavel Loiko, Petra Becker, Ladislav Bohatý, Christoph Liebald, Mark Peltz, sophie vernay, Daniel Ritz, Josep Maria Serres, Xavier Mateos, Yicheng Wang, Xiaodong Xu, Jun Xu, Arkady Major, Alexander Baranov, Uwe Griebner, and Valentin Petrov

Doc ID: 293414 Received 24 Apr 2017; Accepted 15 May 2017; Posted 15 May 2017  View: PDF

Abstract: We studied the refractive index and dispersive properties of the tetragonal rare-earth calcium aluminates, CaLnAlO4 (Ln = Gd or Y). Sellmeier equations were derived for the spectral range of 0.35-2.1 μm. The group velocity dispersion (GVD) in CaGdAlO4 is positive at ~1 µm, 95 fs2/mm, and negative at ~2 µm, –40 fs2/mm. The values of GVD for CaYAlO4 are similar. In addition, thermo-optic coefficients, dn/dT, and thermal coefficients of the optical path were determined for CaYAlO4. dn/dT is negative at ~1 µm, dno/dT = -7.8 and dne/dT = -8.7×10-6 K-1. Thermo-optic dispersion formulas were constructed. The obtained data are of key importance for the design of high-power mode-locked oscillators at ~1 and ~2 µm based on such laser hosts.

Narrow-linewidth carbon nanotube emission in silicon hollow-core photonic crystal cavity

Thi Hong Cam Hoang, Elena Duran Valdeiglesias, Carlos Alonso Ramos, samuel serna, Weiwei Zhang, Marco Balestrieri, Al-Saleh Keita, Niccolò Caselli, Francesco Biccari, Xavier LE ROUX, Arianna Filoramo, Massimo Gurioli, Laurent Vivien, and Eric Cassan

Doc ID: 294806 Received 27 Apr 2017; Accepted 15 May 2017; Posted 15 May 2017  View: PDF

Abstract: Polymer-sorted semiconducting single-walled carbon nanotubes (SWNTs) provide room-temperature emission at near-infrared wavelengths, with potential for large volume production of high quality solutions and wafer-scale deposition. These features make SWNTs a very attractive material for the realization of on-chip light sources. Coupling SWNT into optical microcavities could enhance their emission through the Purcell effect, while enabling spectral selection by cavity resonance engineering. This could allow the realization of bright, narrow-band sources. Here, we report the first demonstration of coupling SWNTs into Si hollow-core photonic crystal cavities. We exploit the strong light-matter interaction in these resonators to enhance SWNT emission, coupling it into an integrated access waveguide. Based on this concept, we demonstrate narrowband SWNT emission resonantly coupled into a Si bus waveguide with a full-width at half maximum of 0.34 nm and an off-resonance rejection exceeding 5 dB.

Rapid direct laser writing of desired plasmonic nanostructures

Ngoc Diep Lai, Quang Cong Tong, Mai Hoang Luong, Jacqueline Remmel, Minh Thanh Do, and Dam Thuy Trang Nguyen

Doc ID: 292764 Received 14 Apr 2017; Accepted 15 May 2017; Posted 16 May 2017  View: PDF

Abstract: We demonstrate a direct way to realize arbitrary gold nanostructures via a local dewetting method. This technique was based on the optically induced local thermal effect at the focusing region of a direct laser writing (DLW) system employing a green continuous-wave laser. The local high temperature allowed the creation of gold nano-islands only at the focusing area of the optical system. By moving the focusing spot, this DLW method allowed us to "write" desired 2D gold patterns, with a feature size down to sub-lambda. A heat model was also proposed to theoretically explain the localized heating process of the absorbing gold layer. Preliminary results were demonstrated for data storage and color printer applications

Characterization of Optical Frequency Transfer Over 154 km of Aerial Fiber

David Gozzard, Sascha Schediwy, Bruce Wallace, Romeo Gamatham, and Keith Grainge

Doc ID: 290228 Received 07 Mar 2017; Accepted 15 May 2017; Posted 15 May 2017  View: PDF

Abstract: We present measurements of the frequency transfer stability and analysis of the noise characteristics of an optical signal propagating over aerial suspended fiber links up to 153.6 km in length. The measured frequency transfer stability over these links is on the order of 10^−11 at an integration time of one second dropping to 10^−12 for integration times longer than 100 s. We show that wind-loading of the cable spans is the dominant source of short-timescale noise on the fiber links. We also report an attempt to stabilize the optical frequency transfer over these aerial links.

Experimental study on the statistic characteristics of 3x3 RF MIMO channel over a single conventional multimode fiber

Yi Lei, Jianqiang Li, Rui Wu, Yuting Fan, Songnian Fu, Feifei Yin, Yitang Dai, and Kun Xu

Doc ID: 291534 Received 31 Mar 2017; Accepted 15 May 2017; Posted 15 May 2017  View: PDF

Abstract: Based on the observed random fluctuation phenomenon of speckle pattern across multimode fiber (MMF) facet and received optical power distribution across three output ports, we experimentally investigate the statistic characteristics of a 3×3 radio frequency (RF) multiple-input multiple-output (MIMO) channel enabled by mode-division-multiplexing (MDM) in conventional 50um MMF using non-mode-selective 3D-waveguide photonic lanterns (PLs) as mode multiplexer and demultiplexer. The impacts of mode coupling on the MIMO channel coefficients, channel matrix, and channel capacity have been analyzed over different fiber length. The results indicate that, spatial multiplexing is benefiting from the greater fiber length with stronger mode coupling despite of higher optical loss.

Dynamics of trapped atoms around an optical nanofiber probed through polarimetry

PABLO SOLANO, Fredrik Fatemi, Luis Orozco, and Steven Rolston

Doc ID: 291225 Received 24 Mar 2017; Accepted 14 May 2017; Posted 15 May 2017  View: PDF

Abstract: The evanescent field outside an optical nanofiber (ONF) can create optical traps for neutral atoms. We present a non-destructive method to characterize such trapping potentials. An off-resonance linearly polarized probe beam that propagates through the ONF experiences a slow axis of polarization produced by trapped atoms on opposite sides along the ONF. The transverse atomic motion is imprinted onto the probe polarization through the changing atomic index of of refraction. By applying a transient impulse, we measure a time-dependent polarization rotation of the probe beam that provides both a rapid and non-destructive measurement of the optical trapping frequencies

Compressible 1D photonic crystal nanolasers with wide wavelength tuning

Tsan-Wen Lu, Chia-Cheng Wu, Chun Wang, and Po-Tsung Lee

Doc ID: 290848 Received 21 Mar 2017; Accepted 14 May 2017; Posted 15 May 2017  View: PDF

Abstract: We propose and demonstrate a tunable photonic crystal nanolaser consisting of 1D periodic nanorods wrapped in deformable polydimethylsiloxane. In addition to low-threshold and long-term lasing stability, the nanolaser also displays reproducible and reliable wavelength tuning with a large tunability of 7.7 nm under 1 % compression. By further associating with stretching, a very-wide-wavelength tunable range of 155 nm that almost spans the entire S+C+L telecommunication bands is successfully demonstrated with a single nanolaser device.

Enhanced self-mixing interferometry based on volume Bragg gratings and diode lasers emitting at 405 nm wavelengths

Victor Contreras Loera, Juha Toivonen, and Horacio Martinez

Doc ID: 291498 Received 28 Mar 2017; Accepted 12 May 2017; Posted 12 May 2017  View: PDF

Abstract: Self-mixing interferometry (SMI) represents a robust, self-aligned technique for metrology applications. Recently, it has been shown that the detection of the frequency-modulated (FM) signal enhances the conventional SMI signal based on the amplitude modulation (AM). Here, an all-optical, simple and effective alternative approach to detect the FM self-mixing signal is presented. We demonstrate the enhanced self-mixing approach using a diode laser emitting at 405 nm and a volume Bragg Grating (VBG) to map frequency to intensity modulations for further optical detection. Our approach overcomes the spectral range limitation of the edge filtering approach based on molecular absorption filters since the VBGs can be fabricated at any spectral range.

Development of a high-power blue laser (445 nm) for material processing

Hongze Wang, YUYA NAKASHIMA, RYOUHEI YOSHIDA, Y Kawahito, and kunio shiokawa

Doc ID: 293204 Received 20 Apr 2017; Accepted 12 May 2017; Posted 15 May 2017  View: PDF

Abstract: We report the structure and power density distribution of a 256 W high-power blue laser (445 nm) for material processing. The absorption rate of the blue laser system for steel was 2.75 times that of a single-mode fiber laser system. The characteristics of steel after laser irradiation were determined, validating the potential of this high-power blue laser for material processing, such as welding, heat treatment, and cladding. To our knowledge, this is the first blue laser with a power as high as 256 W.

High-Energy Pulse Stacking via Regenerative Pulse-Burst Amplification

Ignas Astrauskas, Edgar Kaksis, Tobias Flöry, Giedrius Andriukaitis, Audrius Pugzlys, Andrius Baltuska, John Ruppe, Siyun Chen, Almantas Galvanauskas, and Tadas Balciunas

Doc ID: 290581 Received 14 Mar 2017; Accepted 11 May 2017; Posted 12 May 2017  View: PDF

Abstract: Here we present a coherent pulse stacking approach for up-scaling energy of a solid-state femtosecond chirped pulse amplifier. We demonstrate pulse splitting into four replicas, amplification in a burst-mode regenerative Yb:CaF2 amplifier, designed to overcome intracavity optical damage by colliding pulse replicas, and coherent combining into a single milli-Joule level pulse. Thresholds of pulse-burst-induced damage of optical elements are experimentally investigated. The scheme allows achieving an enhancement factor of 2.62 using a single stage stacker cavity and potentially much higher enhancement factors using cascaded stacking.

Demonstration of intradyne BPSK optical free-space transmission in representative atmospheric turbulence conditions for worst-case geostationary uplink channel

Janis Surof, Juraj Poliak, and Ramon Mata Calvo

Doc ID: 291101 Received 28 Mar 2017; Accepted 11 May 2017; Posted 12 May 2017  View: PDF

Abstract: Binary phase shift keying (BPSK) optical transmission in the C-band with coherent intradyne reception is demonstrated over a long range (10.45~km) link through the atmosphere. The link represents worst-case channel conditions for geostationary (GEO) optical feeder up-links in satellite communications. The digital signal processing used in recovering the transmitted data and the performed measurements are described. Finally, the bit-error-rate (BER) results for 10 Gbit/s, 20 Gbit/s and 30 Gbit/s of the outdoor experiments are presented and compared with back-to-back measurements and theory.

Silicon PAM-4 optical modulator driven by two binary electrial signals with different peak-to-peak voltages

lingchen zheng, jianfeng ding, Sizhu Shao, Lei Zhang, and Lin Yang

Doc ID: 291973 Received 04 Apr 2017; Accepted 11 May 2017; Posted 12 May 2017  View: PDF

Abstract: We demonstrate a silicon PAM-4 optical modulator, which is based on a symmetric Mach-Zehnder interferometer. Two uncorrelated binary electrical signals with different peak-to-peak voltages are applied to the phase shifters of the silicon optical modulator. Accordingly, two different phase shifts are generated in the two arms. After the permutation, there are totally four phase differences between the two arms and the output optical power has four levels. The device can work at 32 Gbaud in the wavelength range from 1525 nm to 1565 nm, which is promising for the next-generation high-speed silicon optical link.

Optical modulation based on tunable light absorption and amplification in metasurfaces coupled with gain medium

Borislav Vasic and Rados Gajic

Doc ID: 292508 Received 10 Apr 2017; Accepted 11 May 2017; Posted 12 May 2017  View: PDF

Abstract: While previous tunable metasurfaces were based mainly on tuning of dielectric permittivity or losses in associated tunable elements, here we propose gain assisted tunable metasurfaces as optical modulators with high ON-OFF ratio. They consist of a dye doped film placed within metal-insulator-metal (MIM) cavities. Plasmonic modes with enhanced electric field significantly enhance both absorption and emission of light by dye molecules. As a result, it is possible to achieve the perfect absorption in MIM cavities with zero reflection, as well as to compensate losses thus achieving unit reflection. The resulting ON/OFF ratio is more than 100, whereas in the case of the lasing from metasurfaces with increased optical gain, this ratio can be even larger.

Compact coupling scheme to achieve the synchronously dual self-mode-locked operation at 946 and 1064 nm

H. P. Cheng, T. L. Huang, C. L. Sung, Chun-Yu Cho, H. C. Liang, and Yung-Fu Chen

Doc ID: 291411 Received 27 Mar 2017; Accepted 11 May 2017; Posted 15 May 2017  View: PDF

Abstract: A synchronously dual self-mode-locked (SML) operation at 946 and 1064 nm is experimentally accomplished by using a compact coupling scheme to obtain the optical beating frequency up to 35.2 THz. The SML emissions at 946 and 1064 nm are established by a monolithic Nd:YAG cavity and a Nd:YVO4 crystal in a flat-flat cavity, respectively. Two gain media are butt adjoined to be longitudinally pumped by a single laser diode. The monolithic Nd:YAG crystal is used not only as the 946-nm laser cavity but also as the output coupler of the Nd:YVO4 1064-nm laser. More importantly, the output surface of the monolithic Nd:YAG laser is coated to generate the optical feedback for the synchronization of the dual SML operation. At a pump power of 10.7 W, the output powers at 1064 and 946 nm can simultaneously reach 1.5 W by controlling the focal position of the pump waist.

Soliton-plasma nonlinear dynamics in mid-IR gas-filled hollow-core fibers

MD SELIM HABIB, Christos Markos, Ole Bang, and Morten Bache

Doc ID: 292228 Received 06 Apr 2017; Accepted 10 May 2017; Posted 12 May 2017  View: PDF

Abstract: We investigate numerically soliton-plasma interaction in a noble-gas-filled silica hollow-core anti-resonant fiber pumped in the mid-IR at 3.0 μm. We observe multiple soliton self-compression stages due to distinct stages where either the self-focusing or the self-defocusing nonlinearity dominates. Specifically, the parameters may be tuned so the competing plasma self-defocusing nonlinearity only dominates over the Kerr self-focusing nonlinearity around the soliton self-compression stage, where the increasing peak intensity on the leading pulse edge initiates a competing self-defocusing plasma nonlinearity acting nonlocally on the trailing edge, effectively preventing soliton-formation there. As the plasma switches off after the self-compression stage, self-focusing dominates again, initiating another soliton self-compression stage in the trailing edge. This process is accompanied by supercontinuum generation spanning 1-4 μm. We find that the spectral coherence drops as the secondary compression stage is initiated.

Wake Mode Sidebands and Instability in Modelocked Lasers with Slow Saturable Absorbers

Shaokang Wang, Shaokang Wang, Curtis Menyuk, Stefan Droste, Laura Sinclair, Ian Coddington, Nathan Newbury, and Thomas Carruthers

Doc ID: 285829 Received 31 Jan 2017; Accepted 10 May 2017; Posted 11 May 2017  View: PDF

Abstract: Passively modelocked lasers with semiconductor saturable absorption mirrors are attractive comb sources due to their simplicity, excellent self-starting properties, and their environmental robustness. These lasers, however, can have an increased noise level and wake mode instabilities. Here, we investigate the wake mode dynamics in detail using a combination of evolutionary and dynamical methods. We describe the modelocked pulse generation from noise when a stable pulse exists and the evolution of the wake mode instability when no stable pulse exists. We then calculate the dynamical spectrum of the modelocked pulse, and we show that it has six discrete eigenmodes, two of which correspond to wake modes. The wake modes are unstable when the wake mode eigenvalues have a positive real part. We also show that even when the laser is stable, the wake modes lead to experimentally-observed sidebands.

Brighter CARS hypermicroscopy via “spectral surfing” of a Stokes supercontinuum

Jeremy Porquez, Ryan Cole, Joel Tabarangao, and Aaron Slepkov

Doc ID: 291586 Received 29 Mar 2017; Accepted 10 May 2017; Posted 11 May 2017  View: PDF

Abstract: We present a simple technique that significantly enhances the interaction of pump pulses with a supercontinuum Stokes generated by nonlinear fibre for time-gated experiments such as coherent anti-Stokes Raman scattering (CARS). The enhancement is achieved through a synchronized power-tuning/time-delay scheme that we call spectral surfing. In this work, we introduce spectral surfing and demonstrate how its application to an economical CARS hypermicroscopy scheme increases brightness, contrast, and spectral scanning range, while potentially reducing sample light exposure.

Electro-optical effects of high aspect ratio P3HT nanofibers colloid in polymer micro-fluid cells

Gleb Lobov, Aleksandrs Marinins, Reza Shafagh, Yichen Zhao, Wouter van der Wijngaart, Lech Wosinski, Muhammet Toprak, Tommy Haraldsson, Mikael Ostling, and Sergei Popov

Doc ID: 292225 Received 05 Apr 2017; Accepted 10 May 2017; Posted 10 May 2017  View: PDF

Abstract: This paper reports the electro-optical (EO) effect of Poly(3-hexylthiophene-2,5-diyl) (P3HT) nanofibers colloid in a polymer micro-fluidic EO cell. P3HT nanofibers are high aspect ratio semiconducting nanostructures, that can be collectively aligned by an external alternating electric field. Due to their high inner crystallinity, P3HT nanofibers possess a strong anisotropy, i.e. dichroic absorption in various ranges of the optical spectrum. According to our results, the degree of alignment reaches a maximum at 0.6 V/μm of electric field strength, which implies a big polarizability value due to geometry and electrical properties of P3HT nanofibers. We believe that 1D crystalline organic nanostructures have a large potential in EO devices due to their significant anisotropy, wide variety of properties, low actuation voltages and opportunity to be tailored via adjustment of the fabrication process.

Single-shot chemical detection and identification with compressed hyperspectral Raman imaging

Jonathan Thompson, Joel Bixler, Brett Hokr, Gary Noojin, Marlan Scully, and Vladislav Yakovlev

Doc ID: 293280 Received 20 Apr 2017; Accepted 09 May 2017; Posted 09 May 2017  View: PDF

Abstract: Raman imaging is a powerful method to identify and detect chemicals. But the long acquisition time required for full spectroscopic Raman images limits many practical applications. Compressive sensing and compressed ultrafast photography have recently demonstrated the acquisition of multi-dimensional data sets with single-shot detection. In this letter we demonstrate the utilization of compressed sensing for single shot compressed Raman imaging. In particular, we use this technique to demonstrate the identification of two similarly white substances in one image via the recovered two-dimensional array of Raman spectra. This technique can be further extended by coupling the compressed sensing apparatus with a microscope for compressed hyperspectral imaging microscopy.

Graphene based Plasmonic Modulator on a Groove-Structured Metasurface

Yulin Wang, Tao Li, and Shining Zhu

Doc ID: 292704 Received 11 Apr 2017; Accepted 09 May 2017; Posted 11 May 2017  View: PDF

Abstract: Graphene holds a great potential to provide efficient modulation in optoelectronic integrated circuits due to its excellent tunablity in conductivity and several types of graphene-based photonic modulators have already been demonstrated. In this work, a plasmonic modulator was proposed based on a groove-structured metasurface covered by a single layer graphene sheet, in which a transverse electrical (TE) like mode is accommodated. Our design takes advantage of field enhancement of plasmonic mode, and overcomes the orientation mismatch between electrical field of the free surface plasmons and the graphene plane. Therefore, this graphene based plasmonic modulator exhibits greatly improved modulation depth compared with the conventional plasmonic ones. Our theoretical results also show this modulator can work in a broadband with acceptable insertion loss, indicating possible applications in nanophotonic integrations.

Robust Real-time 3D Single Particle Tracking Using a Dynamically Moving Laser Spot

Shangguo Hou, Xiaoqi Lang, and Kevin Welsher

Doc ID: 290892 Received 17 Mar 2017; Accepted 09 May 2017; Posted 11 May 2017  View: PDF

Abstract: Real-time 3D single particle tracking uses optical feedback to lock-on to freely diffusing nanoscale fluorescent particles, permitting precise 3D localization and continuous spectroscopic interrogation. Here, we describe a new method of real-time 3D single particle tracking wherein a diffraction-limited laser spot is dynamically swept through the detection volume in three dimensions using a 2D electro-optic deflector and a tunable acoustic gradient lens. This optimized method, (3D Dynamic Photon Localization Tracking, 3D-DyPLoT) enables high speed real-time tracking of single silica coated non-blinking quantum dots (~30 nm diameter) with diffusive speeds exceeding 10 µm2/s at count rates as low as 10 kHz, as well as single YFP-labelled virus-like particles. The large effective detection area (1 µm x 1 µm x 4 µm) allows the system to easily pick up fast-moving particles, while still demonstrating high localization precision (σx = 6.6 nm, σy = 8.7 nm, σz = 15.6 nm). Overall, 3D-DyPLoT provides a fast and robust method for real-time 3D tracking of fast and lowly emitting particles, based on a single excitation and detection pathway, paving the way to more widespread application to relevant biological problems.

Optical biopsy approach to basal cell carcinoma and melanoma based on all-optically integrated photoacoustic and optical coherence tomography

Wangting Zhou, Zhongjiang Chen, Sihua Yang, and Da Xing

Doc ID: 290914 Received 17 Mar 2017; Accepted 09 May 2017; Posted 12 May 2017  View: PDF

Abstract: Basal cell carcinoma (BCC) and melanoma (MM), with the highest morbidity and mortality respectively, are considered as two concerned skin cancers in dermatology. Histological studies have demonstrated that vascular patterns and collagenous stroma serve as key parameters for BCC and MM classification. In this Letter, we sought to identify BCC and MM based on dual-parameters of vascular patterns and scattering structures provided by all-optically integrated photoacoustic and optical coherence tomography (AOPA/OCT). The imaging capability of the AOPA/OCT was verified by the mimic phantoms. Furthermore, in vivo characterization of vasculatures and tissue structures from BCC and MM mice were successfully achieved with high-resolution. Results prove the feasibility of AOPA/OCT as a novel method to dedicate to the in vivo biopsy of skin cancers, which shows new insights into study of skin diseases in early stage.

Highly efficient passively Q-switched Tm:YAP laser using a Cr:ZnS saturable absorber

Brian Cole and Lew Goldberg

Doc ID: 292470 Received 21 Apr 2017; Accepted 09 May 2017; Posted 15 May 2017  View: PDF

Abstract: We describe a diode pumped, passively Q-switched 2 µm Tm:YAP laser generating 10.5W of average power. The laser utilized a Cr:ZnS saturable absorber with a non-saturated transmission T0 of 90\%, and exhibited record 46% optical slope efficiency and a 42% overall optical conversion efficiency, both measured relative to the incident 794nm pump power. At maximum average output power, the laser generated 0.6mJ Q-switched pulses with a maximum peak power of 32 kW. Pulse duration varied between 20ns and 53ns, depending on operating wavelength and pump power. A laser with a T0=80\% saturable absorber generated 1.45mJ Q-switched pulses with a peak power of 138kW.

Interferometric Time-Domain Ptychography for Ultrafast Pulse Characterization

Janne Hyyti, Esmerando Escoto, Gunter Steinmeyer, and Tobias Witting

Doc ID: 291133 Received 21 Mar 2017; Accepted 09 May 2017; Posted 15 May 2017  View: PDF

Abstract: A novel pulse characterization method is presented, favorably combining interferometric frequency-resolved optical gating (FROG) and time-domain ptychography. This new variant is named ptychographic-interferometric frequency-resolved optical gating (πFROG). The measurement device is simple, bearing similarity to standard second-harmonic FROG, yet with a collinear beam geometry and an added bandpass filter in one of the correlator arms. The collinear beam geometry allows tight focusing and circumvents possible geometrical distortion effects of noncollinear methods, making πFROG especially suitable for the characterization of unamplified few-cycle pulses. Moreover, the direction-of-time ambiguity afflicting most second-order FROG variants is eliminated. Possible group delay dispersion of pulses leads to a characteristic tilt in the πFROG traces, allowing the detection of uncompensated dispersion without a retrieval. Using nanojoule, three-cycle pulses at 800 nm, the πFROG method is tested, and the results are compared with spectral phase interferometry for direct electric field reconstruction measurements. Measured pulse durations agree within a fraction of a femtosecond. As a further test, the πFROG measurements are repeated with added group delay dispersion, and found to accurately reproduce the dispersion computed with Sellmeier equations.

Dual-axis optical coherence tomography for deep tissue imaging

Yang Zhao, Will Eldridge, Jason Maher, Sanghoon Kim, Michael Crose, MOHAMED IBRAHIM, Howard Levinson, and Adam Wax

Doc ID: 293094 Received 19 Apr 2017; Accepted 09 May 2017; Posted 16 May 2017  View: PDF

Abstract: We have developed dual-axis optical coherence tomography (DA-OCT) which enables deep tissue imaging by using a novel off-axis illumination/detection configuration. DA-OCT offers a 100-fold speed increase compared to its predecessor, multispectral multiple-scattering low coherence interferometry (ms2/LCI), by using a new beam scanning mechanism based on a microelectrical-mechanical system (MEMS) mirror. The data acquisition scheme was altered to take advantage of this scanning speed, producing tomographic images at a rate of 4 frames (B-scans) per second. DA-OCT differs from ms2/LCI in that the dual axes intersect at a shallower depth (~1mm). This difference, coupled with the faster scanning speed shifts the detection priority from multiply scattered to ballistic light. The utility of this approach was demonstrated by imaging both ex vivo porcine ear skin and in vivo rat skin from a Macfarlane flap model. The enhanced penetration depth provided by the DA-OCT system will be beneficial to various clinical applications in dermatology and surgery.

Super-resolution in diffractive imaging from hemispherical elastic light scattering data

Sergiy Lysenko, Valeriy Sterligov, Manuel GONÇALVES, Armando Rua, Iaroslav Grytsaenko, and Felix Fernandez

Doc ID: 291443 Received 28 Mar 2017; Accepted 09 May 2017; Posted 16 May 2017  View: PDF

Abstract: Angle-resolved hemispherical elastic light scattering techniques have been used to reconstruct the surface profile of two-dimensional photonic crystals with submicron resolution and metrological precision. Iterative algorithms permit subsequent calculation of surface autocorrelation function with additional numerical approximation of power spectrum and then yield final reconstruction of the surface shape. The proposed method enables filtering out unwanted scattering background which precludes the convergence of phase-retrieval algorithms. The estimation of higher harmonics in power spectrum provides the reconstruction of a realistic surface achieving subwavelength resolution.

BDK-doped-core microstructured PMMA optical fiber for effective Bragg grating photo-inscription

Xuehao Hu, Getinet Woyessa, Damien Kinet, Jakob Janting, Kristian Nielsen, Ole Bang, and Christophe Caucheteur

Doc ID: 293424 Received 24 Apr 2017; Accepted 08 May 2017; Posted 12 May 2017  View: PDF

Abstract: An endlessly single-mode doped microstructured poly(methyl methacrylate) (PMMA) optical fiber is produced for effective fiber Bragg grating (FBG) photo-inscription by means of a 400 nm femtosecond pulsed laser and the phase mask technique. The fiber presents a uniform benzyl dimethyl ketal (BDK) distribution in its core, without drastic loss increase. It was produced using the selected center hole doping technique and the BDK dopant acts as a photoinitiator. In this work, we report a rapid growing process of the grating reflection band. For 11 mW mean laser power, the FBG reflectivity reaches 83 % in only 40 seconds.

Frequency comb generation in SNAP bottle resonators

Sergey Suchkov, Misha Sumetsky, and Andrey Sukhorukov

Doc ID: 290270 Received 08 Mar 2017; Accepted 08 May 2017; Posted 08 May 2017  View: PDF

Abstract: We develop a theory of optical frequency comb generation in ultra-compact Surface Nanoscale Axial Photonic (SNAP) bottle microresonators, employing the nonlinear interaction of whispering gallery modes which are confined along an optical fiber with nanoscale radius variation. We predict that a SNAP microresonator with a few-µm radius can generate a frequency comb with an ultra-fine sub-GHz spectral spacing, which would require traditional ring resonators of cm radius. We identify regimes of stable or quasi-periodic comb dynamics due to soliton excitation, and also show that special engineering of the SNAP radius profile can be used to compensate nonlinearity induced dispersion.

Temperature independent optical transition with sub-nanometer linewidth in thermally diffused Gd in GaN

Pratim Saha, Shonal Chouksey, Swaroop Ganguly, and Dipankar Saha

Doc ID: 291695 Received 30 Mar 2017; Accepted 08 May 2017; Posted 08 May 2017  View: PDF

Abstract: We have demonstrated temperature independent optical transitions from thermally diffused Gd in GaN. The emission wavelength is sub-bandgap with respect to GaN. The origin of photon generation is identified as atomic transitions in Gd hosted in the weak interaction field of GaN. The emission linewidth remains sub-nanometer (0.1-0.6 nm) from 19 – 300 K for all the optical pumping intensity. The shift in wavelength with temperature and optical pumping is negligible (~0.8 nm) for the entire temperature window. The output intensity is found to scale linearly with pumping power. The magnetic, electrical and physical characterizations indicate Gd acts as electron traps in GaN. Transient absorption spectroscopy discovers a major non-radiative parallel path for carrier leaking. The observed characteristics may find potential applications in narrow line-width optical sources.

Light-induced self-written waveguide fabrication using 1550 nm laser light

Hidetaka Terasawa, Freddy Tan, Okihiro Sugihara, Akari Kawasaki, Daisuke Inoue, Tatsuya Yamashita, Manabu Kagami, Olivier Maury, Yann BRETONNIERE, and Chantal Andraud

Doc ID: 293012 Received 19 Apr 2017; Accepted 07 May 2017; Posted 15 May 2017  View: PDF

Abstract: Light-induced self-written (LISW) optical waveguides were fabricated for the first time to our knowledge using a photopolymerizable resin system formed by 1550 nm pulse laser light. A two-photon absorption (TPA) chromophore with a TPA cross-section of several hundred GM at 1550 nm was used. Furthermore, the optical interconnection between a single-mode fiber and fiber Bragg grating was demonstrated by the present technique, using one-way irradiation of 1550 nm laser light through the single-mode fiber. The LISW waveguide formation using 1550 nm laser light offers a new and promising alternative route for optical interconnection in silicon photonics technology.

Transverse Anderson localization of surface plasmon polaritons

Zlata Cherpakova, Felix Bleckmann, Tim Vogler, and Stefan Linden

Doc ID: 291635 Received 29 Mar 2017; Accepted 05 May 2017; Posted 05 May 2017  View: PDF

Abstract: We investigate the effect of disorder on the propagation of surface plasmon polaritons in arrays of evanescently coupled dielectric loaded surface plasmon polariton waveguides. Diagonal disorder is implemented by randomly varying the heights of the waveguides. Real-space as well as Fourier-space images of the surface plasmon polariton intensity distribution in the waveguide arrays are recorded by leakage radiation microscopy. With these techniques we experimentally demonstrate the transverse localization of surface plasmon polaritons with increasing disorder.

Polynomials of Gaussians and vortex-Gaussian beamsas complete, transversely confined bases

Rodrigo Gutiérrez-Cuevas and Miguel Alonso

Doc ID: 292259 Received 06 Apr 2017; Accepted 04 May 2017; Posted 04 May 2017  View: PDF

Abstract: A novel type of discrete basis for paraxial beams is proposed,consisting of monomial vortices times polynomialsof Gaussians in the radial variable. These baseshave the distinctive property that the effective size oftheir elements is roughly independent of element order,meaning that the optimal scaling for expanding alocalized field does not depend significantly on truncationorder. This behavior contrasts with that of basescomposed of polynomials times Gaussians, such asHermite-Gauss and Laguerre-Gauss modes, where thescaling changes roughly as the inverse square root ofthe truncation order.

Nonlinear optical response in molecular nitogen:from ab-initio calculations to optical pulse simulations

Anand Bahl, Vinay Majety, A. Scrinzi, and Miroslav Kolesik

Doc ID: 292643 Received 14 Apr 2017; Accepted 04 May 2017; Posted 04 May 2017  View: PDF

Abstract: Using first-principle multi-electron calculations via the hybridanti-symmetrized coupled channels method, we create a modelto describe both the nonlinear polarization and ionization of the nitrogen molecule. Based on the metastable electronic state approach, it is designed for space and time resolved simulations in nonlinear optics that require modeling of optical pulses that exhibit rich spectraldynamics and propagate over long distances. As a demonstration of the model's utility, we study low-order harmonic generation in mid-infrared optical filaments.

Generation of unipolar half-cycle pulse via unusual reflection of a single-cycle pulse from an optically thin metallic or dielectric layer

Anton Pakhomov, Mikhail Arkhipov, Rostislav Arkhipov, Ihar Babushkin, Ayhan Demircan, Uwe Morgner, and Nikolai Rozanov

Doc ID: 286576 Received 15 Feb 2017; Accepted 04 May 2017; Posted 04 May 2017  View: PDF

Abstract: We propose a strikingly simple method to form approximately unipolar half-cycle optical pulses via reflection of a single-cycle optical pulse from an optically thin flat metallic or dielectric layer. Unipolar pulses in reflection arise due to specifics of effectively one-dimensional pulse propagation. Namely, we show that in considered system the field emitted by a flat medium layer is proportional to the velocity of oscillating medium charges instead of their acceleration as it is usually the case. When the single-cycle pulse interacts with linear optical medium, the oscillation velocity of medium charges can be then forced to keep constant sign throughout the pulse duration. Our results essentially differ from that for the direct mirror reflection and suggest a possibility of unusual transformations of the few-cycle light pulses in linear optical systems.

Ultrasensitive Inverse-Weak-Value Tilt Meter

Julian Martinez, Christopher Mullarkey, John Howell, Gerardo Viza, and WeiTao Liu

Doc ID: 285027 Received 19 Jan 2017; Accepted 04 May 2017; Posted 24 May 2017  View: PDF

Abstract: We present an interferometric technique for measuring ultra-small tilts. The information of a tilt in one of the mirrors of a modified Sagnac interferometer is carried by the phase difference between the counter propagating laser beams. Using a small misalignment of the interferometer, orthogonal to the plane of the tilt, a bimodal (or two-fringe) pattern is induced in the beam's transverse power distribution. By tracking the mean of such a distribution, using a split detector, a sensitive measurement of the phase is performed. With 1.2 mW of continuous-wave laser power, the technique has a shot noise limited sensitivity of 56 frad/$\sqrt{\mbox{Hz}}$, and a measured noise floor of 200 frad/$\sqrt{\mbox{Hz}}$ for tilt frequencies above 2 Hz. A tilt of 200 frad corresponds to a differential displacement of 4.0 fm in our setup. The novelty of the protocol relies on signal amplification due to the misalignment, and on good performance at low frequencies. A noise floor of about 70 prad/$\sqrt{\mbox{Hz}}$ is observed between 2 and 100 mHz.

Optimal Mueller matrix estimation in the presence of additive and Poisson noise for any number of illumination and analysis states

Francois Goudail

Doc ID: 290506 Received 10 Mar 2017; Accepted 03 May 2017; Posted 08 May 2017  View: PDF

Abstract: We investigate the optimal strategies for estimating the Mueller matrix with arbitrary numbers of illumination and analysis states, in the presence of signal-independent additive noise or signal-dependent Poisson shot noise. We demonstrate that the architectures that minimize and equalize the estimation variances for both types of noise sources are based on spherical designs of order 2 or 3, and we provide closed-form expressions of the estimation precision obtained with these optimal measurement strategies. The obtained results are important to design Mueller polarimeters in practice and assess their fundamental limits in terms of estimation precision.

Vectorial extreme events in VCSEL polarization dynamics

Chi-Hak UY, Damien RONTANI, and Marc Sciamanna

Doc ID: 292426 Received 24 Apr 2017; Accepted 03 May 2017; Posted 10 May 2017  View: PDF

Abstract: We report on the occurrence of extreme events in the polarization dynamics of vertical cavity surface emitting lasers (VCSEL) with optical feedback. We have identified two types of extreme events based on numerical simulations : vectorial and scalar events corresponding, respectively to the emission of highpower pulse in both linear polarization modes simultaneously and in single linear-polarized mode. We demonstrate that these two types of events follow the typical statistics of rogue waves. Finally, we observe that an emission in both polarization leads to a larger generation rate of extreme events with a saturation over a wide range of feedback strength by comparison to a single polarization mode emission.

Dual-Page Reproduction to Increase Data Transfer Rate in Holographic Memory

Tetsuhiko Muroi, Yutaro Katano, Nobuhiro Kinoshita, and Norihiko Ishii

Doc ID: 291242 Received 23 Mar 2017; Accepted 02 May 2017; Posted 08 May 2017  View: PDF

Abstract: To increase the reproduced data transfer rate in holographic memory, we have investigated simultaneous reproduction of two data pages. By irradiating s- and p-polarization reference beams whose angle gap is equal to the angle between neighboring data pages in angle-multiplexed holograms, two different data pages can simultaneously be reproduced with a bit error rate low enough to decode. This technology is effective to double the data transfer rate in holographic memory.

Observation of robust flat-band localization in driven photonic rhombic lattices

Sebabrata Mukherjee and Robert Thomson

Doc ID: 291139 Received 22 Mar 2017; Accepted 01 May 2017; Posted 02 May 2017  View: PDF

Abstract: We demonstrate that a flat-band state in a quasi-one-dimensional rhombic lattice is robust in the presence of external drivings along the lattice axis. The lattice was formed by periodic arrays of evanescently coupled optical waveguides, and the external drivings were realized by modulating the paths of the waveguides. We excited a superposition of flat-band eigenmodes at the input and observed that this state does not diffract in the presence of static as well as high-frequency sinusoidal drivings. This robust localization is due to destructive interference of the analogous wavefunction and is associated with the symmetry in the lattice geometry. We then excited the dispersive bands and observed Bloch oscillations and coherent destruction of tunneling respectively.

Low Loss Kagome Hollow Core Fibers Operating from the Near- to the Mid-IR

Natalie Wheeler, Thomas Bradley, John Hayes, Marcelo Gouveia, Sijing Liang, Yong Chen, Seyed Reza Sandoghchi, Seyed Mohammad Abokhamis Mousavi, Francesco Poletti, Marco Petrovich, and David Richardson

Doc ID: 285820 Received 31 Jan 2017; Accepted 28 Apr 2017; Posted 04 May 2017  View: PDF

Abstract: We report the fabrication and characterization of Kagome hollow core antiresonant fibers with reduced attenuation, low bend loss and high modal purity. Record low attenuation values are reported: 12.3 dB/km, 13.9 dB/km and 9.6 dB/km in three different fibers optimized for operation at 1 µm, 1.55 µm and 2.5 µm respectively. These fibers are excellent candidates for ultrahigh power delivery at key laser wavelengths including 1.064 µm and 2.94 µm, as well as for applications in gas-based sensing and non-linear optics.

Temperature dependence mitigation in stationary Fourier-transform on-chip spectrometers

alaine herrero, Aitor Velasco, Hugh Podmore, Pavel Cheben, Jens Schmid, Siegfried Janz, Maria Calvo, Dan-Xia Xu, Alan Scott, and Pedro Corredera

Doc ID: 291293 Received 24 Mar 2017; Accepted 28 Apr 2017; Posted 04 May 2017  View: PDF

Abstract: We present two techniques for mitigating the effects of temperature drifts in waveguide spatial heterodyne Fourier-transform on-chip spectrometers. In high-resolution devices, large optical path length differences result in an increased sensitivity to temperature variations and impose stringent requirement on the thermal stabilization system. In order to overcome this limitation, here we experimentally demonstrate two new temperature mitigation techniques based on a temperature-sensitive calibration and phase errors correction. The spectrometer chip under analysis comprises an array of 32 Mach-Zehnder interferometers fabricated on a silicon-on-insulator platform. The optical path delays are implemented as microphotonic spirals of linearly increasing length up to 3.779 cm, yielding a spectral resolution of 17 pm. We demonstrate that the degradation in retrieved spectra caused by temperature drift is effectively eliminated by temperature-sensitive calibration and phase errors correction.

Nanosecond difference-frequency-generation in orientation-patterned gallium phosphide

Wei Junxiong, Chaitanya Kumar Suddapalli, Hanyu Ye, Kavita Devi, Peter Schunemann, and Majid Ebrahim-Zadeh

Doc ID: 287372 Received 23 Feb 2017; Accepted 25 Apr 2017; Posted 10 May 2017  View: PDF

Abstract: We report a tunable, single-pass, pulsed nanosecond difference-frequency-generation (DFG) source based on the new semiconductor nonlinear material, orientation-patterned gallium phosphide (OP-GaP). The DFG source is realized by mixing the output signal of a nanosecond OPO tunable over 17 -1827 nm with the input pump pulses of the same OPO at 1064 nm in an OP-GaP crystal, resulting in tunable generation over 3 nm in the mid-infrared from 2548 to 2781 nm. Using a 40-mm-long crystal, we have produced ~14 mW of average DFG output power at 2719 nm for a pump power of 5 W and signal power of 1 W at 80 kHz repetition rate. To the best of our knowledge, this is the first single-pass nanosecond DFG source based on OP-GaP. The DFG output beam has a TEM00 spatial mode profile and exhibits passive power stability better than 1.7% rms over 1.4 hours at 2774 nm, compared to 1.6% and 0.1% rms for the signal and pump, respectively. The OP-GaP crystal is recorded to have a temperature acceptance bandwidth of 17.7 ºC.

Speed limits of structured illumination microscopy

Florian Stroehl and Clemens Kaminski

Doc ID: 291735 Received 31 Mar 2017; Accepted 23 Apr 2017; Posted 05 May 2017  View: PDF

Abstract: A theoretical framework for widefield structured illumination microscopy (SIM) reconstruction from fewer than the commonly used nine raw frame acquisitions is introduced and applied in silico and in vitro. The proposed scheme avoids the recording of redundant spatial frequency components, which was necessary in previous SIM algorithms. This allows for gentler superresolution imaging at faster speeds. A doubling of frame rates is possible solely via changes in the computational reconstruction procedure. Furthermore, we explore numerically the effect of sample movement on the quality reconstruction and the number of raw frames recordable. Our results show that there exists a limit above which deconvolution microscopy becomes superior to SIM.

Absolute non-invasive measurement of CO2 mole fraction emitted by E. coli and S. aureus using calibration-free 2f WMS applied to a 2004 nm VCSEL

Zarin S., Arup Chakraborty, and abhishek upadhyay

Doc ID: 281991 Received 23 Dec 2016; Accepted 12 Apr 2017; Posted 13 Apr 2017  View: PDF

Abstract: We report the first demonstration of accurate real-time non-invasive measurement of the absolute cumulative mole fraction of metabolic carbon dioxide emitted by Escherichia coli and Staphylococcus aureus over a period of several hours of their life cycles using a recently-developed calibration-free wavelength modulation spectroscopy technique. A 1mW vertical cavity surface emitting laser is used to interrogate a single rotational vibrational absorption line of carbon dioxide at 2003.5 nm. The measurements are immune to laser intensity fluctuations due to variable optical coupling that is inevitable in such free-space coupled experiments that run over 10-18 hours. The cumulative carbon dioxide mole fraction follows the characteristic modified Gompertz model that is typical of bacterial growth in batch cultures. The various characteristics growth parameters are extracted from this curve. The technique can be readily extended to study multiple volatile organic compounds that bacteria are known to emit.

Self-starting dropout-free harmonic mode-locked soliton fiber laser with low timing jitter

Qiang Hao, Yunfeng Wang, Peng Luo, Hong Hu, and Heping Zeng

Doc ID: 290806 Received 15 Mar 2017; Accepted 02 Apr 2017; Posted 24 May 2017  View: PDF

Abstract: We demonstrate a simple but robust self-starting environmentally-stable passively harmonic mode-locked femtosecond Er-fiber laser with a scalable repetition rate of up to 10th harmonic and >50 dB of supermode suppression. The repetition rate of short- and long-term operation for each harmonic appears no pulse dropout. Furthermore, as low as 0.8 and 2.1 mHz standard deviation the repetition rate is achieved by using the pump-induced nonlinearity to modulate the refractive index of the gain fiber.

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