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Accepted papers to appear in an upcoming issue

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

Fiber-feedback OPO for half-harmonic generation of sub-100-fs frequency combs around 2μm

Kirk Ingold, Alireza Marandi, Michel Digonnet, and Robert Byer

Doc ID: 240510 Received 20 May 2015; Accepted 27 Aug 2015; Posted 27 Aug 2015  View: PDF

Abstract: We demonstrate a femtosecond fiber-feedback optical parametric oscillator (OPO) at degeneracy. The OPO cavity comprises an 80-cm long fiber composed of a combination of a combination of normal and anomalous dispersion sections providing a net intracavity group delay dispersion close to zero. Using a mode-locked Yb-fiber laser as the pump, we achieved half-harmonic generation of 250-MHz, 1.2-nJ nearly-transform-limited 97-fs pulses at 2090 nm with a total conversion efficiency of 36%.

Dispersion of coupled mode-gap cavities

Jin Lian, Sergei Sokolov, Sylvain Combrié, Alfredo De Rossi, Emre Yuce, and Allard Mosk

Doc ID: 243898 Received 29 Jun 2015; Accepted 26 Aug 2015; Posted 27 Aug 2015  View: PDF

Abstract: The dispersion of a CROW made of photonic crystal mode-gap cavities is pronouncedly asymmetric. This asymmetry cannot be explained by the standard tight binding model. We show that the fundamental cause of the asymmetric dispersion is the fact that the cavity mode profile itself is dispersive, i.e., the mode wave function depends on the driving frequency, not the eigenfrequency. This occurs because the photonic crystal cavity resonances do not form a complete set. By taking into account the dispersive mode profile, we formulate a mode coupling model that accurately describes the asymmetric dispersion without introducing any new free parameters.

Controllable all-fiber orbital angular momentum mode converter

Shuhui Li, Qi Mo, Cheng Du, Xiao Hu, and Jian Wang

Doc ID: 245564 Received 08 Jul 2015; Accepted 26 Aug 2015; Posted 27 Aug 2015  View: PDF

Abstract: We present a scheme to realize controllable, scalable, low-cost and versatile all-fiber orbital angular momentum (OAM) converter. The converter consists of a two-mode fiber (TMF) with its input terminal welded with a single-mode fiber (SMF), a mechanical long period grating (LPG), a mechanical rotator, metal flat slabs and a fiber polarization controller. The LPG is employed to convert fundamental fiber mode to higher-order modes and the flat slabs are used to stress the TMF to adjust relative phase difference between two orthogonal higher-order modes. Selective conversion from LP01 mode to LP11a, LP11b, OAM-1 or OAM+1 mode is demonstrated in the experiment.

Critical angle based sensor with improved figure of merit using dip detection

Ibrahim Abdulhalim, Ibrahim Watad, Mohammad Jabalee, and Amir Aizen

Doc ID: 247180 Received 31 Jul 2015; Accepted 26 Aug 2015; Posted 27 Aug 2015  View: PDF

Abstract: It is demonstrated theoretically and experimentally that a one dimensional photonic crystal (1D-PC) made of quarter waves stack on top of a prism exhibits both TE and TM resonances that coincide with the critical angle c when the 1D-PC is semi-infinite and with very little deviation from c for a finite 1D-PC. As a refractive index sensor it behaves as a total internal reflection sensor at c with the advantage of detecting a narrow dip rather than an edge and enhanced figure of merit by increasing the number of periods in the 1D-PC. Using the diverging beam approach on an optical bench a two channels sensor is demonstrated with sensitivity of 120.9 deg/RIU and detection limit of 1.9x10-5RIU.

Stabilized Phase Detection of Heterodyne Sum Frequency Generation for Interfacial Studies

Yi Rao, Bolei Xu, YAJING WU, Dezheng Sun, and Hai-Lung Dai

Doc ID: 247673 Received 11 Aug 2015; Accepted 26 Aug 2015; Posted 27 Aug 2015  View: PDF

Abstract: We present here a collinear-geometry heterodyne sum frequency generation (HD-SFG) for interfacial studies. The HD detection is based on a collinear SFG configuration, in which a picosecond visible and a femtosecond IR beam first produce a strong local oscillator (LO), and then generate weak SFG signals from interface samples. A time-delay compensator, consisting of an MgF2 window, is placed before the samples to introduce the time delay between the local oscillator and the interfacial SFG signals for spectral interferometry (SI). Our HD-SFG method exhibits advantages of long-time phase stability, unsusceptible to sample heights, reflection correction-free, and easy-to-implement.

Unveiling the photonic spin Hall effect of freely propagating fan-shaped cylindrical vector vortex beams

yi zhang, Peng Li, Sheng Liu, and Jianlin Zhao

Doc ID: 245772 Received 10 Jul 2015; Accepted 24 Aug 2015; Posted 24 Aug 2015  View: PDF

Abstract: An intriguing photonic spin Hall effect (SHE) for a freely paraxially propagating fan-shaped cylindrical vector (CV) vortex beam is theoretically and experimentally studied. A developed model to descript this kind of photonic SHE for fan-shaped CV vortex beam is proposed based on angular spectrum diffraction theory. With this model, the close dependences of spin-dependent splitting on the azimuthal order of polarization, the topological charge of spiral phase and the propagation distance are accurately revealed. Furthermore, this kind of controllable photonic SHE is experimentally verified by measuring the Stokes parameters.

Wide-field optical coherence microscopy of the mouse brain slice

Eunjung Min, JUNWON LEE, ANDREY VAVILIN, SUNWOO JUNG, SUNGWON SHIN, jeehyun kim, and Woonggyu Jung

Doc ID: 245792 Received 10 Jul 2015; Accepted 24 Aug 2015; Posted 24 Aug 2015  View: PDF

Abstract: The imaging capability of optical coherence microscopy (OCM) has a great potential to be used in neuroscience research, because it is able to visualize the brain’s anatomic features without labeling or external contrast agents. However, the field-of-view of OCM is still narrow, which dilutes the strength of OCM and limits its application. In this study, we present fully automated wide-field OCM for mosaic imaging of sliced mouse brains. A total of 308 segmented OCM images were acquired, stitched, and reconstructed as an en-face brain image after intensive imaging processing. The overall imaging area was 11.2 mm × 7.0 mm (horizontal × vertical) and the corresponding pixel resolution was 1.2 μm × 1.2 μm. OCM images were compared to traditional histology using samples stained with Nissl and Luxol fast blue (LFB). In particular, the orientation of the fibers associated with myelinated disease was analyzed and quantified in wide-field OCM.

Novel multilayer bandpass filter with extended lower and upper stopbands

Boris Belyaev and Vladimir Tyurnev

Doc ID: 246954 Received 29 Jul 2015; Accepted 24 Aug 2015; Posted 25 Aug 2015  View: PDF

Abstract: We propose a novel design for a multilayer bandpass filter in which every resonant dielectric layer is separated from adjacent dielectric layers or from the environment by a nonresonant grating of strip conductors on the layer interface. Here every grating acts as a mirror with specified transparency. Relative to the conventional multilayer bandpass filter with multilayer dielectric mirrors, the proposed filter has multiply extended stopbands below and above the passband. Additionally, we provide formulas for computing the filter’s frequency response. A comparison between the computed frequency responses for the proposed and conventional filters with the same passband is presented.

.5 billion counts per second time correlated single photon counting using CMOS SPAD arrays

Nikola Krstajic, Simon Poland, James Levitt, Richard Walker, Ahmet Erdogan, Simon Ameer-Beg, and Robert Henderson

Doc ID: 243285 Received 18 Jun 2015; Accepted 22 Aug 2015; Posted 24 Aug 2015  View: PDF

Abstract: We present a digital architecture for fast acquisition of time correlated single photon counting (TCSPC) timestamps from a 32×32 CMOS SPAD array (Megaframe) to the computer memory. Custom firmware was written to transmit timestamp codes from 1024 TCSPC-enabled pixels for fast transfer of TCSPC timestamps. Our 1024 channel TCSPC system is capable of acquiring up to 0.5 billion TCSPC timestamps per second with 16 histogram bins spanning 14 ns width. Other options include 320 million TCSPC timestamps per second with 256 histogram bins spanning either 14 ns or 56 ns time windo. We present a wide-field fluorescence microscopy setup demonstrating fast fluorescence lifetime data acquisition. To the best of our knowledge, this is the fastest direct TCSPC transfer from a single photon counting device to the computer to date.

Monolithically Integrated Dual-Channel Coherent Receiver with Widely Tunable Local Oscillator for 100 Gbps DP-QPSK Applications

Phillip Skahan, Sarat Gundavarapu, Douglas Baney, Dan Blumenthal, and Kimchau N. Nguyen

Doc ID: 239933 Received 13 May 2015; Accepted 22 Aug 2015; Posted 24 Aug 2015  View: PDF

Abstract: We report implementation of a monolithically integrated 100 Gbps DP-QPSK wavelength tunable coherent receiver on a 3 mm² die that consists of a tunable C-Band local oscillator with a 40 nm range, eight 30 GHz photodetectors, and two parallel 90° optical hybrids. A BER of 10-³ with an OSNR of 7.5 dB operating at 50 Gbps NRZ-QPSK data per channel for a total capacity of 100 Gbps is reported.

All-silicon nanorod-based Dammann gratings

Guoxing Zheng, Zile Li, Ping an He, Qiling Deng, Song Li, Jiangnan Zhao, and Yong Ai

Doc ID: 242436 Received 10 Jun 2015; Accepted 22 Aug 2015; Posted 24 Aug 2015  View: PDF

Abstract: Previous diffractive optical elements such as Dammann gratings, whose phase profile is controlled by etching different depths into a transparent dielectric substrate, suffer from a contradiction between complexity of fabrication procedures and the performance of gratings. In this letter, we combine the concept of geometric phase and phase modulation in depth, prove both by theoretical analysis and numerical simulation that, nanorod arrays etched on a silicon substrate has characteristic of strong polarization conversion between two circular-polarized states and can act as highly efficient half-waveplate. More importantly, only by changing the orientation angles of each nanorod, the arrays can control the phase of a circular polarized light cell-by-cell. With above principle, we report the realization of a nanorod-based Dammann gratings reaching diffraction efficiencies of (50-52) % in the C-band fiber telecommunications window (1530-1565 nm). In the design, uniform 4×4 spot arrays with an extending angle of 59°×59° can be obtained in the far field. Because of these advantages of one-step fabrication procedure, accurate phase controlling and strong polarization conversion, nanorod-based Dammann gratings could find their markets for various practical applications.

Widely tunable mode-locked fiber laser using carbon nanotube and LPG W-shaped filter

Jie Wang, A. Ping Zhang, Yonghang Shen, Hwa Yaw Tam, and Ping Kong Wai

Doc ID: 245783 Received 10 Jul 2015; Accepted 21 Aug 2015; Posted 21 Aug 2015  View: PDF

Abstract: A widely tunable mode locked fiber laser using a carbon nanotube absorber and a fiber-optic W-shaped spectral filter is presented. The W-shaped filter is constructed by sandwiching a phase-shifted long-period grating between two LPGs of different periods. By adjusting the temperature of the W-shaped filter from 23 to 100°C, the central wavelength of the mode-locked fiber laser can be continuously tuned from 1597 to 1553 nm. The tuning range is further extended to 1531.6 nm when a shorter erbium-doped fiber is used in the fiber oscillator. The experimental results reveal that the large thermal tunability of the proposed LPG filter provides an effective approach to achieve compact widely tunable mode-locked fiber lasers covering both C and L bands.

Circularly Polarized Carrier-Envelope-Phase Stable Attosecond Pulse Generation based on coherent undulator radiation

Gyorgy Toth, Zoltan Tibai, Zsuzsanna Nagy-Csiha, Zsuzsanna Marton, Gabor Almasi, and Janos Hebling

Doc ID: 246133 Received 17 Jul 2015; Accepted 21 Aug 2015; Posted 21 Aug 2015  View: PDF

Abstract: In this Letter, we present a new method for generation of circularly polarized attosecond pulses. According to our calculations, shape controlled, carrier envelope phase stable pulses of several hundred nJ energy could be produced by exploitation of the coherent undulator radiation of an electron bunch. Our calculations are based on an existing particle accelerator system (FLASH II in DESY, Germany). We investigated the energy dependence of the attosecond pulses on the energy of electrons and the parameters of the radiator undulator, which generate the electro-magnetic radiation.

Electromagnetically induced absorption in a non-degenerate three-level ladder system

James Keaveney, Daniel Whiting, Erwan Bimbard, Mark Zentile, Charles Adams, and Ifan Hughes

Doc ID: 246980 Received 30 Jul 2015; Accepted 21 Aug 2015; Posted 21 Aug 2015  View: PDF

Abstract: We investigate, theoretically and experimentally, the transmission of light through a thermal vapour of three-level ladder-type atoms, in the presence of 2 counter-propagating control fields. A simple theoretical model predicts the presence of electromagnetically induced absorption (EIA) in this pure three-level system when the control field is resonant. Experimentally, we use $^{87}$Rb in a large magnetic field of 0.62~T to reach the hyperfine Paschen-Back regime and realise a non-degenerate three-level system. Experimental observations verify the predictions over a wide range of detunings.

Solving the radiative transfer equation with a mathematical particle method

Magnus Neuman, Per Edstrom, and Sverker Edvardsson

Doc ID: 239876 Received 07 May 2015; Accepted 21 Aug 2015; Posted 24 Aug 2015  View: PDF

Abstract: We solve the radiative transfer equation (RTE) using a recently proposed mathematical particle method, originally developed for solving general functional equations. We show that in the case of the RTE it gives several advantages, such as handling arbitrary boundary conditions and phase functions, and avoiding numerical instability in strongly forward scattering media. We also solve the RTE including fluorescence, and an example is shown with a fluorescence cascade, where light is absorbed and emitted in several steps. We show that the evaluated particle method is straightforward to implement, in contrast to many traditional RTE solvers, but a potential drawback is the tuning of the method parameters.

Electromagnetically induced transparency based on guided-mode resonances

Sun-Goo Lee, Soo-Yong Jung, Hee-Seung Kim, Seihyoung Lee, and Jong-Moon Park

Doc ID: 247406 Received 06 Aug 2015; Accepted 20 Aug 2015; Posted 20 Aug 2015  View: PDF

Abstract: We present a novel electromagnetically induced transparency system based on guided-mode resonances and numerically demonstrate its transmission characteristics through finite-difference time-domain simulations. The system is composed of two planar dielectric waveguides and a subwavelength grating. It is shown that by the coupling between two resonant guide-modes with a low- and high-quality factor, respectively, a narrow transparency window is generated inside a broad background transmission dip produced by the guided-mode resonance. Our work could provide another efficient way toward the realization of electromagnetically induced transparency.

A frequency-tunable optoelectronic oscillator using a dual-mode amplified feedback laser as an electrically controlled active microwave photonic filter

Dan Lu, Biwei Pan, Haibo Chen, and Ling-Juan Zhao

Doc ID: 243187 Received 17 Jun 2015; Accepted 20 Aug 2015; Posted 24 Aug 2015  View: PDF

Abstract: A widely tunable optoelectronic oscillator (OEO) based on a self-injection-locked monolithic dual-mode amplified feedback laser (DM-AFL) is proposed and experimentally demonstrated. In the proposed OEO structure, the DM-AFL functions as an active tunable microwave photonic filter (MPF). By tuning the injection current applied on the amplifier section of the AFL, tunable microwave outputs ranging from 32 GHz to 41 GHz, and single sideband phase noises below −97 dBc/Hz @ 10 kHz offset from the carriers are realized.

Ho3+/Er3+ co-doped fluoride glass sensitized by Tm3+ pumped by a 1550 nm laser diode for efficient 2.0 μm laser applications

Feifei Huang, ying tian, Junjie Zhang, Shiqing Xu, and Huanhuan Li

Doc ID: 246010 Received 15 Jul 2015; Accepted 20 Aug 2015; Posted 24 Aug 2015  View: PDF

Abstract: In present paper, a high emission intensity of 2.0 μm is reported of Er3+/Ho3+ co-doped fluoride glass sensitized by Tm3+ ions under 1550 nm excitation. The measured absorption spectra do not show clustering in the local ligand field, which also demonstrates that Er3+ ions are efficiently excited by pumpings and transfer energy (ET) to Ho3+ and Tm3+ ions. The enhanced Ho3+: 2.0 μm emission has a maximum emission cross section (4.8 ×10-21 cm2). An ET mechanism based on the enahnced 2.0 μm emission and other reduced near-infrared emissions is discussed. Results show that the addition of Tm3+ ions populates the Ho3+: 5I7 level through channel at the Tm3+: 3F4 level between Er3+ and Ho3+ ions. The spectroscopic characteristics and thermal property of Er3+/Ho3+/Tm3+ tri-doped ZBYA glass reveal that the material is an attractive host for 2.0 μm lasers.

Shaping of Light Beams by 3D Direct Laser Writing on Facets of Nonlinear Crystals

shlomi lightman, Raz Gvishi, Ady Arie, and Gilad Hurvitz

Doc ID: 244019 Received 13 Jul 2015; Accepted 20 Aug 2015; Posted 26 Aug 2015  View: PDF

Abstract: We demonstrate experimentally spatial-mode conversions of light beams generated in a quadratic nonlinear process by micron-scale structures placed on the facets of the nonlinear crystals. These structures were printed on the crystal facets using a 3D direct laser writing system. The functional structures were designed to modify the phase of the beam at specific wavelengths, thereby enabling conversion of a fundamental Gaussian laser beam into different high order Hermite-Gauss modes, Laguerre-Gaussian modes and zero-order Bessel beams of the second harmonic. This facet functionalization opens exciting new opportunities for robust and compact beam shaping in a nonlinear interaction, without compromising the conversion efficiency.

Surface Plasmon Coupling for Suppressing p-GaN Absorption and TM-polarized Emission in a Deep-UV Light-emitting Diode

Chih-Chung Yang, Yang Kuo, Chia-Ying Su, Chieh Hsieh, Wen-Yen Chang, Chu-An Huang, and Yean-woei Kiang

Doc ID: 246802 Received 28 Jul 2015; Accepted 19 Aug 2015; Posted 20 Aug 2015  View: PDF

Abstract: The radiated power enhancement (suppression) of an in- (out-of-) plane-oriented radiating dipole at a desired emission wavelength in the deep-ultraviolet (UV) range when it is coupled with a surface plasmon (SP) resonance mode induced on a nearby Al nanoparticle (NP) is demonstrated. Also, it is found that the enhanced radiated power mainly propagates in the direction from the Al NP toward the dipole. Such SP coupling behaviors can be used for suppressing the transverse-magnetic-polarized emission, enhancing the transverse-electric-polarized emission, and reducing the UV absorption of the p-GaN layer in an AlGaN-based deep-UV light-emitting diode by embedding a sphere-like Al NP in its p-AlGaN layer.

Superluminal propagation through 500 m optical fiber via stimulated Brillouin scattering

Li Zhan, Liang Zhang, Minglei Qin, Zhiqiang Wang, Hao Luo, and Tantan Wang

Doc ID: 242728 Received 10 Jun 2015; Accepted 19 Aug 2015; Posted 20 Aug 2015  View: PDF

Abstract: We experimentally demonstrate superluminal propagation through 500 m optical fibers based on stimulated Brillouin scattering (SBS), which is the longest superluminal propagating distance to the best of our knowledge. Brillouin-induced loss resonance for fast light generation is achieved in a single frequency Brillouin lasing oscillator with a highly nonlinear fiber (HNLF) as Brillouin media. The single frequency operation is realized by embedding a saturable absorber (SA) fiber loop with unpumped Erbium-doped fiber (EDF). Consequently, the Gaussian signal light experiences a maximum advancement of 1330 ns, corresponding to a large fractional advancement of 1.87.

Highly Coherent Modeless Broadband Semiconductor Laser

mohamed sellahi, Arnaud Garnache, Mikhaël Myara, Isabelle Sagnes, and Grégoire Beaudoin

Doc ID: 243109 Received 18 Jun 2015; Accepted 19 Aug 2015; Posted 20 Aug 2015  View: PDF

Abstract: We report on highly-coherent modeless broadband continuous wave operation of a semiconductor vertical-external-cavity-surface-emitting-laser. The laser design is based on a frequency-shifted-feedback scheme provided by an acousto-optics frequency shifter inserted in a linear or a ring cavity. The gain mirror is a GaAs-based multiple quantum well structure providing large gain at 1.07 μm wavelength. This efficient laser exhibits a coherent optical spectrum over 1.15 nm (300 GHz) bandwidth, with 70 mW output power and a beam close to diffraction limit (M² < 2). The light polarization is linear (> 30 dB extinction ratio). The frequency noise spectral density shows a 1st order low-pass like shape (100 kHz cut-off) which gives a Gaussian form for homodyne interferometric beat signals. The measured beat width is ~ 78 kHz which gives a coherence time of ~ 13 μs. No parasitic non-linear light-matter interactions are observed, showing a dynamics very close to published theory.

Solid Hemoglobin-Polymer Phantoms for Evaluation of Biophotonic Systems

Hyounguk Jang, T. Joshua Pfefer, and Yu Chen

Doc ID: 243825 Received 02 Jul 2015; Accepted 18 Aug 2015; Posted 20 Aug 2015  View: PDF

Abstract: Stable tissue phantoms that incorporate the spectral absorption properties of hemoglobin would benefit a wide range of biophotonic technologies. Towards this end, we have developed and validated a novel polymer material incorporating hemoglobin. Our solid hemoglobin-polymer (SHP) material is fabricated by mixing liquid silicone base with a hemoglobin solution, followed by sonication and low temperature curing. The absorption coefficients of cured samples were determined over the 450-1000 nm wavelength range using the inverse adding-doubling method. Measurements indicated SHP optical stability over four months. Near-infrared spectroscopy and hyperspectral imaging measurements of SHP samples were performed to demonstrate the utility of this approach. SHP materials have the potential to vastly improve tissue-simulating phantoms used for development, evaluation, and standardization of optical devices for oximetry and other applications.

Dispersive waves induced by self-defocusing temporal solitons in a BBO crystal

Morten Bache and Binbin Zhou

Doc ID: 245642 Received 09 Jul 2015; Accepted 18 Aug 2015; Posted 20 Aug 2015  View: PDF

Abstract: We experimentally observe dispersive waves in the anomalous dispersion regime of a BBO crystal, induced by a self-defocusing few-cycle temporal soliton. Together the soliton and dispersive waves form an energetic octave-spanning supercontinuum. The soliton was excited in the normal dispersion regime of BBO through a negative cascaded quadratic nonlinearity. Using pump wavelengths from 1.24-1.4 μm, dispersive waves are found from 1.9-2.2 μm, agreeing well with calculated resonant phase-matching wavelengths due to degenerate four-wave mixing to the soliton. We also observe resonant radiation from non-degenerate four-wave mixing between the soliton and a probe wave, which was formed by leaking part of the pump spectrum into the anomalous dispersion regime. Through simulations we confirm the experimental results.

Quantitative imaging of microvascular blood flow networks in deep cortical layers by 1310nm μODT

Jiang You, Qiujia Zhang, Ki Park, Congwu Du, and Yingtian Pan

Doc ID: 242462 Received 09 Jun 2015; Accepted 18 Aug 2015; Posted 20 Aug 2015  View: PDF

Abstract: Abstract: There is growing interest in new neuroimage techniques that permit not only high-resolution quantification of cerebral blood flow velocity (CBFv) in capillaries but also a large field of view to map the CBFv network dynamics. Such image capabilities are of great importance for decoding the functional difference across multiple cortical layers under stimuli. To tackle the limitation of optical penetration depth, we present a new ultrahigh-resolution optical coherence Doppler tomography (µODT) system at 1310nm and compare it with a prior 800nm µODT system for mouse brain 3D CBFv imaging. We show that the new 1310nm µODT allows for dramatically increased depth (~4 times) of quantitative CBFv imaging to 1.4mm, thus covering the full thickness of mouse cortex (i.e., layers I-VI). Interestingly, we show that such a unique 3D CBFv imaging capability allows us to identify microcirculatory redistribution across different cortical layers resulting from repeated cocaine exposures.

Infrared hot-carrier photodetection based on planar perfect absorber

Xiaofeng Li, Kai Wu, Cheng Zhang, Shaolong Wu, and Yaohui Zhan

Doc ID: 246632 Received 24 Jul 2015; Accepted 18 Aug 2015; Posted 20 Aug 2015  View: PDF

Abstract: Hot carrier based photodetectors are independent on the semiconductor bandgap, thus paving a new paradigm of photovoltaic conversion. Herein, we propose a non-nanostructured and multilayered metal/insulator/TCO/silica/reflector system, and explored detailedly the optical response and the electrical transport in the device via the finite-element electromagnetic simulation and the probability-based analytical carrier-transport calculation. Results show that the planar system can function as a planar perfect absorber at the targeted wavelength under the inbuilt cavity resonance, with a very high tunability by tailoring the cavity length and the metal thickness. Moreover, a strong asymmetrical absorption is formed in the two electrode-layers, yielding strong unidirectional photocurrents and output power densities. This study suggests a more simple and feasible way to realize hot-carrier infrared photodetectors.

High-order microring resonator with perfect transmission using symmetric Fibonacci structures

Wen-Jeng Hsueh, C. W. Tsao, and Y. H. Cheng

Doc ID: 245707 Received 09 Jul 2015; Accepted 17 Aug 2015; Posted 20 Aug 2015  View: PDF

Abstract: A symmetric Fibonacci microring resonator (SFMR) has been presented to avoid the coupled resonator optical waveguide (CROW) bottle, which is a bottle-shaped distribution for high orders in transmission spectra. The SFMR features three advantages which improve filtering quality compared to that provided by traditional periodic microring resonators. First, sharper resonances are obtained by eliminating the CROW bottle from the mini gaps that appear in the major-band region. Second, peaks with perfect transmission are always obtained without radius and coupling modulation in the mini-band regions and major-band regions. Third, the full width at half-maximum of the band-edge peak decreases with increasing generation order.

A diode laser operating on atomic transition limited by an isotope 87Rb Faraday filter at 780 nm

Jingbiao Chen, zhiming tao, Yelong Hong, Bin Luo, and Hong Guo

Doc ID: 241544 Received 25 May 2015; Accepted 17 Aug 2015; Posted 18 Aug 2015  View: PDF

Abstract: We demonstrate an extended cavity Faraday laser system using an anti-reflection coated laser diode (ARLD) as gain medium and the isotope 87Rb Faraday anomalous dispersion optical filter (FADOF) as frequency selective device. Using this method, the laser wavelength works stably at the highest transmission peak of the isotope 87Rb FADOF over the laser diode current from 55 mA to 140 mA and the temperature from 15 ◦C to 35 ◦C. Neither the current nor the temperature of the laser diode has significant influence on the output frequency. Compared with previous extended cavity laser systems operating at frequencies irrelevant to spectacular atomic transition lines, the laser system realized here provides a stable laser source with frequency operating on atomic transitions for many practical applications.

Comparative analysis of four-wave mixing of optical pulses in slow and fast light regimes of a silicon photonic crystal waveguide

Nicolae Panoiu and Spyros Lavdas

Doc ID: 241928 Received 28 May 2015; Accepted 17 Aug 2015; Posted 18 Aug 2015  View: PDF

Abstract: We present an in-depth study of four-wave mixing (FWM) of optical pulses in silicon photonic crystal waveguides. Our analysis is based on a rigorous model that includes all relevant linear and nonlinear optical effects and their dependence on the group-velocity, as well as the influence of free-carriers on pulse dynamics. In particular, we reveal key differences between FWM in the slow- and fast-light regimes and how they are related to the physical parameters of the pulses and waveguide. Finally, we illustrate how these results can be used to design waveguides with optimized FWM conversion efficiency.

Tunable frequency-up/down conversion in gas-filled hollow-core photonic crystal fibers

Mohammed Saleh and Fabio Biancalana

Doc ID: 242825 Received 16 Jun 2015; Accepted 17 Aug 2015; Posted 18 Aug 2015  View: PDF

Abstract: Based on the interplay between photoionization and Raman effect in gas-filled photonic crystal fibers, we propose a new optical device to control frequency-conversion of ultrashort pulses. By tuning the input-pulse energy, the output spectrum can be either down-converted, up-converted, or even frequency-shift compensated. For low input energies, Raman effect is dominant and leads to a redshift that increases linearly during propagation. For larger pulse energies, photoionization starts to take over the frequency conversion process, and induces a strong blueshift. We have found also that by changing the fiber-output pressure the pulse spectrum redshifts, providing an additional degree of freedom in the design.

Demonstration of high-energy, narrow-bandwidth, and temporally shaped fiber regenerative amplifier

Zhi Qiao, Wei Fan, Xiaochao Wang, and Zunqi Lin

Doc ID: 243049 Received 16 Jun 2015; Accepted 17 Aug 2015; Posted 18 Aug 2015  View: PDF

Abstract: We report a high-energy and high-gain fiber regenerative amplifier for narrow-bandwidth nanosecond laser pulses that uses an Yb-doped photonic-crystal fiber. The input pulse energy is 270 pJ for a 3.5-ns laser pulse with 0.1-nm (FWHM) bandwidth. At a pump laser power of 8.6 W at 974 nm, pulse energies up to 746 μJ with 1.2% (rms) energy stability are generated. To our knowledge this is the highest energy obtained in fiber-based regenerative amplifier. A high-energy, nearly diffraction-limited, single-mode beam with a high gain of 64dB shows promise for future application in the front ends of high-power laser facilities.

Optical injection locking based amplification in phase coherent transfer of optical frequencies

Joonyoung Kim, Harald Schnatz, David Wu, Giuseppe Marra, David Richardson, and Radan Slavik

Doc ID: 245555 Received 08 Jul 2015; Accepted 16 Aug 2015; Posted 17 Aug 2015  View: PDF

Abstract: We demonstrate use of an optical injection phase locked loop (OIPLL) as a regenerative amplifier for optical frequency transfer applications. The optical injection locking (OIL) provides high gain within a narrow bandwidth (< 100 MHz), and is capable of preserving the fractional frequency stability of the incoming carrier to better than 10^(-18) at 1000 s. The OIPLL was tested in the field as a mid-span amplifier for the transfer of an ultra-stable optical carrier, stabilized to an optical frequency standard, over a 292 km-long installed dark fiber link. The transferred frequency at the remote end reached a fractional frequency instability of less than 1 × 10^(-19) at averaging time of 3200 s.

Mid-infrared multi-mode absorption spectroscopy using interband cascade lasers for multi-species sensing

Paul Ewart, Henry Northern, Seamus O'Hagan, William Bewley, Jerry Meyer, Chadwick Canedy, Mijin Kim, Chul Soo Kim, Igor Vurgaftman, Charles Merritt, joshua abell, Benjamin Gras, and Benjamin Fletcher

Doc ID: 237479 Received 03 Apr 2015; Accepted 15 Aug 2015; Posted 17 Aug 2015  View: PDF

Abstract: An interband cascade laser (ICL) operating at 3.7 microns has been used to perform multi-mode absorption spectroscopy, MUMAS, at scan rates up to 10 kHz. Linewidths of individual modes in the range 10 - 80 MHz were derived from isolated lines in the MUMAS signatures of HCl. MUMAS data for methane covering a spectral range of 30 nm yielded a detection level of 30 microbar.m for 1 second measurement time at 100 Hz. Simultaneous detection of methane, acetylene and formaldehyde in a gas mixture containing all three species is reported.

Channel add-drop filter based on dual photonic crystal cavities in push-pull mode

Christopher Poulton, Xiaoge Zeng, Mark Wade, and Milos Popovic

Doc ID: 239936 Received 03 Aug 2015; Accepted 15 Aug 2015; Posted 17 Aug 2015  View: PDF

Abstract: We demonstrate an add-drop filter based on a dual photonic crystal nanobeam cavity system that emulates the operation of a traveling-wave resonator and thus provides separation of the through and drop port transmission from the input port. The device is on a 3x3mm chip fabricated in an advanced, microelectronics silicon-on-insulator complementary metal-oxide semiconductor (SOI CMOS) process (IBM 45nm SOI) without any foundry process modifications. The filter shows 1dB insertion loss in the drop port with a 3dB bandwidth of 64GHz, and 16dB extinction in the through port. To the best of our knowledge, this is the first implementation of a port-separating add-drop filter based on standing wave cavities coupled to conventional waveguides, and demonstrates a performance that suggests potential for photonic crystal devices within optical immersion lithography-based advanced CMOS electronics-photonics integration.

Focal varying microlens array

Hong-Bo Sun, Zhen-Nan Tian, Wen-Gang Yao, Jun-Jie Xu, Yan-Hao Yu, and Qi-Dai Chen

Doc ID: 244165 Received 02 Jul 2015; Accepted 15 Aug 2015; Posted 17 Aug 2015  View: PDF

Abstract: We report a novel microlens array with different curvature unit lenses (MLADC) fabricated with femtosecond laser direct writing technology. The MLADC consisted of hexagonal hyperboloid unit microlenses, which have different heights and curvatures from others. The unique optical performance of imaging and focusing capability were demonstrated. An object was imaged at different positions from MLADC by unit lenses, as the ability of adjusting curvature of image plane for overall MLADC. In addition, experiment had a good agreement with simulation results, which based on the analysis of finite element method. The novel MLADC will have important applications in improving performance of optical systems, especially in field curvature correction and real-time three-dimensional imaging.

Tunable type II intracavity difference frequency generation at 5.4 μm in a two chip vertical external cavity surface emitting laser

Michal Lukowski, Robert Bedford, Mahmoud Fallahi, and Chris Hessenius

Doc ID: 245356 Received 06 Jul 2015; Accepted 15 Aug 2015; Posted 17 Aug 2015  View: PDF

Abstract: We report on the generation and experimental demonstration of intracavity type II difference frequency generation (DFG) in a two chip InGaAs/GaAs vertical external cavity surface emitting laser. The presented two chip cavity provides two orthogonally polarized, independently tunable, high intensity lasing modes with emission around 970 nm and 1170 nm. A silver thiogallate nonlinear crystal is inserted in the common collinear folded region of the cavity to generate output in mid-IR spectral band. The independent tunability of each fundamental color allows for more than 100 nm of tuning around 5.4 μm DFG signal with CW output power in excess of 5 mW.

High accuracy measurement of the ground-state hyperfine splitting in a ¹¹³Cd+ microwave clock

Kai Miao, Jianwei Zhang, xiaolin sun, Shiguang Wang, aimin zhang, kun liang, and Lijun Wang

Doc ID: 243974 Received 01 Jul 2015; Accepted 14 Aug 2015; Posted 17 Aug 2015  View: PDF

Abstract: A microwave frequency standard based on laser-cooled ¹¹³Cd+ ions has been developed in recent years, and the short-term frequency satbility is measured to be 6.1 ×10¯¹³/fi√τ. By comparing the Cd+ clock to a superior frequency reference, the ground-state hyperfine splitting of ¹¹³Cd+ is measured precisely to be 15199862855.0192(10) Hz with a fractional precision of 6.6 ×10¯¹⁴. This result is consistent with previous results, and the measurement precision is improved by nearly one order than the best result reported before.

Mid-infrared 333-MHz frequency comb continuously tunable from 1.95 – 4.0 µm

Karolis Balskus, Zhaowei Zhang, Richard McCracken, and Derryck Reid

Doc ID: 245961 Received 21 Jul 2015; Accepted 14 Aug 2015; Posted 17 Aug 2015  View: PDF

Abstract: We report a 333-MHz femtosecond optical parametric oscillator in which carrier-envelope offset stabilization was implemented by using a versatile locking technique that allowed the idler comb to be tuned continuously over a mid-infrared range from 1.95 µm to 4.0 µm. A specially designed multi-section and multi-grating periodically-poled KTP crystal provided simultaneously phasematched parametric down-conversion and pump + idler sum-frequency generation, enabling strong heterodyne signals with the pump super-continuum (employed for locking) to be obtained across the tuning range of the device. The idler comb offset was stabilized to a 10-MHz reference frequency with a cumulative phase noise from 1 Hz–64 kHz of <1.3 rad maintained across the entire operating range, and average idler output powers up to 50 mW.

High-power, high-repetition-rate, Yb-fiber laser based femtosecond ultraviolet source at 355 nm

Goutam K. Samanta, Apurv Chaitanya N, Aadhi A, and Jabir M. V.

Doc ID: 246199 Received 16 Jul 2015; Accepted 14 Aug 2015; Posted 17 Aug 2015  View: PDF

Abstract: We report on development of a high-power, high-repetition-rate fiber laser based source of ultrafast ultraviolet (UV) radiation. Using single-pass, second harmonic generation (SHG) and subsequent sum frequency generation (SFG) of an ultrafast Yb-fiber at 1064 nm in 1.2-mm and 5-mm long bismuth borate (BIBO) crystals respectively, we have generated UV output power as high as 1.06 W at 355 nm with single-pass near-IR-to-UV conversion efficiency ~22%. The source has output pulses of temporal and spectral width ~576 fs and 1.6 nm respectively at 78 MHz rep. rate. For given crystal and laser parameters, we have experimentally verified that the optimum conversion efficiency of SFG process requires interacting pump beams to have same confocal parameters. We also present the systematic study on power ratio of pump beams influencing the overall conversion of the UV radiation. The UV source has peak-to-peak short term power fluctuation of <2.2% with a power drift of 0.76%/h associated to different loss mechanisms of BIBO crystal at UV wavelengths. At tight focusing, the BIBO crystal have broad angular acceptance bandwidth (~2 mrad∙cm) for SFG of femtosecond laser.

Efficient mode conversion in guiding structures with longitudinal modulation of nonlinearity

Yaroslav Kartashov, Victor Vysloukh, and Kestutis Staliunas

Doc ID: 245752 Received 10 Jul 2015; Accepted 14 Aug 2015; Posted 18 Aug 2015  View: PDF

Abstract: We describe power-dependent dynamics of conversion of the guided modes of various guiding structures stimulated by a nearly resonant longitudinal modulation of the nonlinear coefficient of the medium. In the case of two interacting modes the dynamics of conversion can be fully periodic, but evolution of weights of guided modes is described in terms of Jacoby elliptical functions, in contrast to dynamics of conversion stimulated by modulation of the linear refractive index, where evolution of mode weights is usually governed by trigonometric functions. It is shown that the control of the energy exchange integrals, as well as of the input weights of the interacting modes is especially crucial for efficient mode conversion in the setting considered here.

Visible-excited CARS-ROA spectroscopy

Kotaro Hiramatsu, Philippe Leproux, Vincent COUDERC, Takashi Nagata, and Hideaki Kano

Doc ID: 242484 Received 08 Jun 2015; Accepted 13 Aug 2015; Posted 17 Aug 2015  View: PDF

Abstract: We developed a Raman optical activity (ROA) spectroscopic system with visible-excited coherent anti-Stokes Raman scattering (CARS). With using supercontinuum in visible generated with a photonic crystal fiber pumped with both 532 nm and 1064 nm, multiplex CARS-ROA spectrum covering the whole fingerprint region is obtained. In the visible excitation, CARS-ROA spectrum of (-)-β-pinene shows higher contrast ratio of the chirality-induced signal to the achiral background than that of the previously reported near-infrared CARS-ROA spectrum.

Fiber laser based on Chalcogenide Microwires

Alaa Al-kadry, Mohammed El Amraoui, Younes Messaddeq, and Martin Rochette

Doc ID: 244139 Received 02 Jul 2015; Accepted 12 Aug 2015; Posted 17 Aug 2015  View: PDF

Abstract: We report the first pulsed fiber laser using a chalcogenide microwire as the nonlinear medium. The laser is passively mode-locked with nonlinear polarization rotation, and can be adjusted for the emission of solitons or noise-like pulses. The use of the microwire leads to a lasing threshold at the microwatt level and shortens the cavity length by 4 orders of magnitude with respect to other lasers of its kind. The controlled birefringence of the microwire, combined with a linear polarizer in the cavity, enable multiwavelength laser operation with tunable central wavelength, switchable wavelength-separation, and variable number of laser wavelengths.

Dielectric Laser Acceleration of Sub-100keV Electrons with Silicon Dual Pillar Grating Structures

Kenneth Leedle, Andrew Ceballos, Huiyang Deng, Olav Solgaard, Fabian Pease, Robert Byer, and James Harris

Doc ID: 246065 Received 15 Jul 2015; Accepted 12 Aug 2015; Posted 17 Aug 2015  View: PDF

Abstract: We present the demonstration of high gradient laser acceleration and deflection of electrons with silicon dual pillar grating structures using both evanescent inverse Smith-Purcell modes and coupled modes. Our devices accelerate sub-relativistic 86.5 keV and 96.3 keV electrons by 2.05 keV over 5.6 μm distance for accelerating gradients of 370 MeV/m with a 3 nJ mode-locked Ti:Sapphire laser. We also show that dual pillars can produce uniform accelerating gradients with a coupled mode field profile. These results represent a significant step towards making practical dielectric laser accelerators for ultrafast, medical, and high energy applications.

Observation of stable vector vortex solitons

Yana Izdebskaya, Gaetano Assanto, and Wieslaw Z. Krolikowski

Doc ID: 246496 Received 27 Jul 2015; Accepted 11 Aug 2015; Posted 17 Aug 2015  View: PDF

Abstract: We report on the first experimental observation of stable vector vortex solitons in nonlocal nonlinear media with a reorientational response, such as nematic liquid crystals. These solitons consist of two co-polarized mutually trapped beams of different colors, a bright fundamental spatial soliton and a nonlinear optical vortex. The nonlinear vortex component which is normally unstable in nonlinear media is stabilized and confined here by the highly nonlocal refractive potential self-induced by the soliton.

Slow-light plasmonic metamaterial based on dressed-state analog of electromagnetically-induced transparency

Søren Raza and Sergey Bozhevolnyi

Doc ID: 241822 Received 27 May 2015; Accepted 11 Aug 2015; Posted 19 Aug 2015  View: PDF

Abstract: We consider a simple configuration for realizing one-dimensional slow-light metamaterials with large bandwidth-delay products using stub-shaped Fabry-Perot resonators as building blocks. Each metaatom gives rise to large group indices due to a classical analog of the dressed-state picture of electromagnetically-induced transparency. By connecting up to eight metaatoms, we find bandwidth-delay products over unity and group indices approaching 100. Our approach is quite general and can be applied to any type of Fabry-Perot resonators and tuned to different operating wavelengths.

High sensitivity refractive index sensor based on a tapered SCSMF structure

Qiang Wu, Dejun Liu, arun kumar mallik, Yuan Jinhui, Chongxiu Yu, Gerald Farrell, and Yuliya Semenova

Doc ID: 242978 Received 15 Jun 2015; Accepted 11 Aug 2015; Posted 11 Aug 2015  View: PDF

Abstract: A high sensitivity refractive index (RI) sensor based on a tapered small core singlemode fiber (SCSMF) structure sandwiched between two traditional singlemode fibers (SMF28) is reported. The microheater brushing technique was employed to fabricate the tapered fiber structures with different waist diameters of 12.5 µm, 15.0 µm and 18.8 µm. Experiments demonstrate that the fiber sensor with a waist diameter of 12.5 µm offers the best sensitivity of 19212.5 nm/RIU (RI unit) in the RI range from 1.4304 to 1.4320. All sensors fabricated in this work show good linearity in terms of the spectral wavelength shift versus changes in RI. Furthermore, the sensor with the best sensitivity to RI was also used to measure relative humidity (RH) without any coating materials applied to the fiber surface. Experimental results show that the spectral wavelength shift changes exponentially as the RH varies from 60% to 95%. A maximum sensitivity of 18.3 nm per relative humidity unit (RHU) was achieved in the RH range from 90.4% to 94.5% RH.

Ultrafast pulses from a mid-infrared fibre laser

Tomonori Hu, Stuart Jackson, and Darren Hudson

Doc ID: 246376 Received 21 Jul 2015; Accepted 10 Aug 2015; Posted 18 Aug 2015  View: PDF

Abstract: Ultrafast laser pulses at mid-infrared wavelengths (2-20 $\mu$m) interact strongly with molecules due to the resonance with their vibration modes. This enables applications in frequency-comb based sensing and laser tissue surgery. To achieve this, fibre lasers are ideal as they are compact, stable and efficient. We extend the performance of these lasers with the production of 6.4 kW at a wavelength of 2.8 $\mu$m, with complete electric field retrieval using Frequency Resolved Optical Gating techniques. Contrary to problems associated with achieving high average power, fluoride fibres have now shown the capability of operating in the ultrafast high-peak power regime.

Growth, spectroscopic and laser performances of 2.79 μm Cr,Er,Pr:GYSGG radiation-resistant crystal

Dunlu Sun, Jianqiao Luo, Huili Zhang, Qiang guo, Zhongqing Fang, Xuyao Zhao, Maojie Cheng, Qing-li Zhang, and Shaotang Yin

Doc ID: 243381 Received 22 Jun 2015; Accepted 10 Aug 2015; Posted 18 Aug 2015  View: PDF

Abstract: We demonstrate the growth, spectroscopic and laser performances of 2.79 μm Cr,Er,Pr:GYSGG radiation-resistant crystal. The lifetimes for the upper laser level 4I11/2 and lower laser level 4I13/2 are 0.59 ms and 0.84 ms, respectively, which are due to the doping of Pr3+ ions. A maximum pulse energy 278 mJ operated at 10 Hz and 2.79 μm is obtained when pumped with flash lamp, corresponding to the electrical-to-optical efficiency 0.6% and slope efficiency 0.7%. A maximum average power 2.9 W at 60 Hz is achieved, corresponding to the electrical-to-optical efficiency 0.4% and slope efficiency 0.8%. Compared with Cr,Er:YSGG crystal, the Cr,Er,Pr:GYSGG crystal can be operated at higher pulse repetition rate. These results suggest that doping deactivator Pr3+ ions can effectively decrease the lower laser level lifetime and improve the laser repetition rate. Therefore, the application fields and range of the Cr,Er,Pr:GYSGG laser can be extended greatly due to its properties of radiation-resistant and high repetition frequency.

Photoswitchable and dye-doped bubble domain texture of cholesteric liquid crystals

Andrii Varanytsia and Liang-Chy Chien

Doc ID: 244283 Received 03 Jul 2015; Accepted 09 Aug 2015; Posted 11 Aug 2015  View: PDF

Abstract: We demonstrate control of the transmittance of the naturally formed bubble domain (BD) texture of cholesteric liquid crystals (CLC) with negative dielectric anisotropy confined into a cell with homeotropic surface anchoring. By using a photosensitive chiral dopant with variable helical twisting power, control of packing density of bubbles, spatial patterning, as well as all-optical switching between bistable states with different optical densities is achieved. By introducing dichroic dye into the CLC mixture, a bistable and switchable by applied electric field guest-host system is obtained. The light-dimming properties of dye-doped BD CLC systems may lead to development of a wide range of applications.

Free-space Optical Communications Using Orbital-Angular-Momentum Multiplexing Combined with MIMO-Based Spatial Multiplexing

Yongxiong Ren, Zhe Wang, Guodong Xie, Long Li, Yinwen Cao, Peicheng Liao, Yan Yan, Nisar Ahmed, Zhe Zhao, Nima Ashrafi, Solyman Ashrafi, Robert Bock, Moshe Tur, Alan Willner, Cong Liu, Roger Linquist, and Andreas Molisch

Doc ID: 241190 Received 25 Jun 2015; Accepted 09 Aug 2015; Posted 17 Aug 2015  View: PDF

Abstract: We explore the potential of combining the advantages of multiple-input multiple-output (MIMO)-based spatial multiplexing with those of orbital angular momentum (OAM) multiplexing to increase the capacity of free-space optical (FSO) communications. We experimentally demonstrate an 80 Gbit/s FSO system with a 2×2 aperture architecture, in which each transmitter aperture contains two multiplexed data-carrying OAM modes. Inter-channel crosstalk effects are minimized by the OAM beams’ inherent orthogonality and by the use of 4×4 MIMO signal processing. Our experimental results show that the bit-error rates can reach below the forward error correction limit of 3.8×10-3 and the power penalties are less than 3.6 dB for all channels after MIMO processing. This indicates that OAM and MIMO-based spatial multiplexing can be compatible with and complement each other, thereby providing the potential for a denser spatially multiplexed FSO system.

Diffuse-light all-solid-state invisibility cloak

Robert Schittny, Andreas Niemeyer, Muamer Kadic, Tiemo Bückmann, Andreas Naber, and Martin Wegener

Doc ID: 243586 Received 24 Jun 2015; Accepted 07 Aug 2015; Posted 17 Aug 2015  View: PDF

Abstract: An ideal invisibility cloak makes arbitrary macroscopic objects within the cloak indistinguishable from its surrounding – for all directions, illumination patterns, polarizations, and colors of visible light. Recently, we have approached such an ideal cloak for the diffusive regime of light propagation using a core-shell geometry and a mixture of water and white wall paint as surrounding. Here, we present an all-solid-state version based on polydimethylsiloxane (PDMS) doped with titania nanoparticles for surrounding/shell and on a high-reflectivity micro-porous ceramic for the core. By virtue of reduced effects of absorption, especially from the core, the cloaking performance and the overall light throughput are improved significantly.

Tunable single-mode coupled-cavity laser in a standard InP photonics platform

Wesley Sacher, Emil Kleijn, Benjamin Taylor, Hasitha Jayatilleka, Luc Augustin, and Joyce Poon

Doc ID: 243705 Received 25 Jun 2015; Accepted 07 Aug 2015; Posted 17 Aug 2015  View: PDF

Abstract: We present a wavelength tunable, coupled-cavity laser in a standard indium phosphide multi-project wafer shuttle which did not support distributed feedback gratings. The single-mode operation was enabled by weak reflections from slots in the laser cavity. The wavelength of the laser emission was tunable over 20 nm near a wavelength of 1560 nm via the currents applied to each section of the laser. A maximum sidemode suppression ratio of 46 dB was observed. The delayed self-heterodyne spectrum of the laser showed a Voigt lineshape, corresponding to optical linewidths of 3.7 MHz for the Lorentzian and 88MHz for Gaussian contributions.

Time-averaged photon-counting digital holography

Nazif Demoli, Hrvoje Skenderovic, and Mario Stipcevic

Doc ID: 243236 Received 17 Jun 2015; Accepted 31 Jul 2015; Posted 03 Aug 2015  View: PDF

Abstract: Time-averaged holography has been using photo-emulsions (early stage) and digital photo-sensitive arrays (later) to record holograms. We extend the recording possibilities by utilizing a photon-counting detector and we further investigate the possibility of obtaining accurate hologram reconstructions in rather severe experimental conditions. To achieve this, we derived an expression for fringe function comprising the main parameters affecting the hologram recording. Influence of the main parameters, namely the exposure time and the number of averaged holograms, is analyzed by simulations and experiments. It is demonstrated that taking long exposure times can be avoided by averaging over many holograms with the exposure times much shorter than the vibration cycle. Conditions in which signal-to-noise ratio in reconstructed holograms can be substantially increased are provided.

PROUD-based method for simple real-time in-line characterization of propagation-induced distortions in NRZ Data Signals

Hugo Martins, Juan Pastor Graells, Luis Romero Cortés, Daniel Piote, Sonia Martin-Lopez, Jose Azana, and Miguel Gonzalez Herraez

Doc ID: 242195 Received 15 Jun 2015; Accepted 29 Jul 2015; Posted 29 Jul 2015  View: PDF

Abstract: A simple, in-line method for real-time full characterization (amplitude and phase) of propagation distortions arising due to group velocity dispersion and self-phase modulation on 10-20 Gbps transmitted NRZ optical signals is reported. It is based on phase reconstruction using optical ultrafast differentiation (PROUD), a linear and self-referenced technique. The flexibility of the technique is demonstrated by characterizing different data stream scenarios. Experimental results were modelled using conventional propagation equations, showing good agreement with the measured data.

Electromagnetic diffraction properties of randomly aligned one-dimensional cylinders

Hiroyuki Ichikawa and Mizuki Ishimoto

Doc ID: 241434 Received 25 May 2015; Accepted 29 Jul 2015; Posted 19 Aug 2015  View: PDF

Abstract: A new approach to electromagnetically analyze random structures is proposed. In increasing a period of grating consisting of deterministic random structure, optical performance of the element approaches to a certain converged value. Thus, characterizing random structures becomes possible in a single run computation without statistical procedure. We demonstrate the performance of the method using one-dimensional cylinder arrays.

Spectroscopic sensing of reflection optical activity in achiral AgGaS2

Oriol Arteaga

Doc ID: 242980 Received 16 Jun 2015; Accepted 28 Jul 2015; Posted 30 Jul 2015  View: PDF

Abstract: Optical activity is a fundamental effect of electrodynamics that was discovered more than 200 years ago. While optical activity is typically recognized by the rotation of the polarization of light as it propagates through a bulk medium, in certain configurations, the specular reflection of light on the surface of a material is also sensitive to its optical activity. Here we show that the ellipsometric analysis of the light reflected at the surface of a gyrotropic but achiral crystal of AgGaS2 allows the spectroscopic determination of its optical activity above the bandgap, where transmission methods are not applicable. This is the first clear spectroscopic determination of reflection optical activity in a crystal and we have measured the largest optical activity ever reported for a natural material. We also demonstrate that normal incidence transmission and reflection measurements probe different aspects of optical activity.

Topological Effects in Anisotropy-Induced Nano-Fano Resonance of a Cylinder

Lei Gao, Dongliang Gao, Andrey Novitsky, Hongli Chen, and Boris Lukyanchuk

Doc ID: 242429 Received 05 Jun 2015; Accepted 28 Jul 2015; Posted 11 Aug 2015  View: PDF

Abstract: We demonstrate that optical Fano resonance can be induced by anisotropy rather than frequency selection under the resonant condition . A tiny perturbation in anisotropy can result in a giant switch in the principal optic axis near surface Plasmon resonance. Such anisotropy-induced Fano resonance shows fast-reversion between forward scattering and backward scattering at the lowest-energy interference. Both near field and far field of the particle change dramatically around Fano resonance. The topology of optical singular points and the trajectory of energy flux reveal distinctly the interaction between incident waves and localized surface Plasmons, which also determine the far-field scattering pattern. The anisotropy-induced Fano resonance and its high sensitivity open new perspectives on light-matter interactions and promises potential applications in biological sensors, optical switch and optomechanics.

Paths correlation matrix

Qian Weixian, Xiaojun Zhou, Yingcheng Lu, and Jiang Xu

Doc ID: 242939 Received 17 Jun 2015; Accepted 27 Jul 2015; Posted 28 Jul 2015  View: PDF

Abstract: Both the Jones and Mueller matrices encounter difficulties when physically modelling mixed materials or rough surfaces due to the complexity of light-matter interactions. To address these issues, we derived a matrix called the paths correlation matrix (PCM), which is a probabilistic mixture of Jones matrices of every light propagation paths. Because PCM is related to actual light propagation paths, it is well suited for physical modeling. Experiments were performed, and the reflection PCM of a mixture of granite and aluminum was measured. The PCM of the mixed sample was accurately decomposed into pure granite’s single reflection, pure aluminum’s single reflection, and depolarization caused by multiple reflections, which is consistent with the theoretical derivation. Reflection parameters of both smooth and rough surface can be calculated from PCM decomposition, and the results fit well with the theoretical calculations provided by the Fresnel equations. These theoretical and experimental analyses verify that PCM is an efficient way to physically model light-matter interactions.

High-directionality fiber-chip grating coupler with interleaved trenches and subwavelength index-matching structure

Daniel benedikovic, Carlos Alonso Ramos, Pavel Cheben, Jens Schmid, shurui wang, Daxia Xu, Jean Lapointe, Siegfried Janz, Robert Halir, Alejandro Ortega-Moñux, J. Gonzalo Wangüemert-Pérez, I. Molina-Fernández, Jean-Marc FEDELI, Laurent Vivien, and Milan Dado

Doc ID: 245508 Received 07 Jul 2015; Accepted 26 Jul 2015; Posted 11 Aug 2015  View: PDF

Abstract: We present the first experimental demonstration of a new fiber-chip grating coupler concept that exploits the blazing effect by interleaving the standard full (220 nm) and shallow etch (70 nm) trenches in a 220-nm-thick silicon layer. The high-directionality is obtained by controlling the separation between the deep and shallow trenches to achieve constructive interference in the upward direction and destructive interference towards the silicon substrate. Utilizing this concept the grating directionality can be maximized independent of the bottom oxide thickness. The coupler also includes a subwavelength-engineered index matching region, designed to reduce the reflectivity at the interface between the injection waveguide and the grating. We report a measured fiber-chip coupling efficiency of -1.3 dB, the highest coupling efficiency achieved to date for a surface grating coupler in 220-nm SOI platform fabricated in a conventional dual-etch process without high-index overlays or bottom mirrors.

Optical injection and spectral filtering of high-power UV laser diodes

Vera Schäfer, Christopher Ballance, Calvin Tock, and David Lucas

Doc ID: 242223 Received 04 Jun 2015; Accepted 20 Jul 2015; Posted 21 Jul 2015  View: PDF

Abstract: We demonstrate injection-locking of 120mW laser diodes operating at 397nm. We achieve stable operation with injection powers of ~100 μW and a slave laser output power of up to 110mW. We investigate the spectral purity of the slave laser light via photon scattering experiments on a single trapped Ca40 ion. We show that it is possible to achieve a scattering rate indistinguishable from that of monochromatic light by filtering the laser light with a diffraction grating to remove amplified spontaneous emission.

Multimode Brillouin spectrum in a long tapered birefringent photonic crystal fiber

Thibaut Sylvestre, Joel Tchahame, Jean Charles Beugnot, and Alexandre Kudlinski

Doc ID: 242349 Received 09 Jun 2015; Accepted 17 Jul 2015; Posted 20 Aug 2015  View: PDF

Abstract: We investigate the stimulated Brillouin scattering (SBS) in a long tapered birefringent solid-core photonic crystal fiber (PCF), where the core size tightens from 2 µm down to 0.8 µm over a length of 124 m. Our results show that the taper induces a broadband and multi-peaked Brillouin spectrum and that the birefringence generates a significant frequency shift of the whole spectrum depending on the input state of polarization. We further measure the Brillouin threshold power and show an increase of 6~dB compared to the same but untapered fiber. Numerical simulations are also presented to account for the taper effect on the Brillouin spectrum. Our findings open a new mean to control or inhibit the SBS by tapering photonic crystal fibers.

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