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Accepted papers to appear in an upcoming issue

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High-Speed All-Optical Pattern Recognition of Dispersive Fourier Images through a Photonic Reservoir Computing Subsystem

Charis Mesaritakis, Adonis Bogris, A. Kapsalis, and Dimitris Syvridis

Doc ID: 237559 Received 06 Apr 2015; Accepted 29 Jun 2015; Posted 29 Jun 2015  View: PDF

Abstract: In this letter we present and fully model a photonic scheme that allows the high-speed identification of images acquired through the dispersive Fourier technique. The proposed setup consists of a photonic reservoir-computing scheme that is based on the nonlinear response of randomly interconnected InGaAsP micro ring resonators. This approach allowed classification errors of 0.6%, whereas it alleviates the need for complex high-cost optoelectronic sampling and digital processing.

Brillouin amplification and processing of the Rayleigh scattering signal

Shmuel Sternklar, David Mermelstein, Eliashiv Shacham, and Moran Biton

Doc ID: 238063 Received 15 Apr 2015; Accepted 29 Jun 2015; Posted 29 Jun 2015  View: PDF

Abstract: Brillouin amplification of Rayleigh scattering is demonstrated using two different configurations. In the first technique, the Rayleigh scattering and amplification occurs simultaneously in the same fiber. In the second technique, the amplification takes place in a second fiber. The differences between the two techniques are delineated. Using the second technique, we demonstrate single-sideband off-resonant Brillouin amplification of the Rayleigh signal. This technique is shown to enhance the SNR of a signal that is due to vibration-induced strain on the fiber.

Angular Spectrum based wave-propagation method with Compact Space Bandwidth for large propagation distances

Tomasz Kozacki and Konstantinos Falaggis

Doc ID: 237878 Received 09 Apr 2015; Accepted 29 Jun 2015; Posted 30 Jun 2015  View: PDF

Abstract: Rigorous propagation methods enable diffraction calculations at a high NA. However for the case of large propagation distances known solutions allow obtain either spatially-resolution limited fields (Rayleigh–Sommerfeld direct integration), or fields with aliasing errors (Angular Spectrum AS). Accurate calculations at high NA require zero padding or upsampling. This paper overcome these problems by introducing a sampling scheme based on compact space bandwidth product representation, which adjust sampling frequency of input field and propagated one according to the evolution of generalized space bandwidth product. This sampling concept allows proposing novel AS method enabling high efficiency, high accuracy and high NA diffraction computations at larger propagation distances without need of zero padding or upsampling. The method has several advantages: (1) high accuracy for larger propagation distances; (2) reduced sampling with minimal computation effort; (3) zooming capability; (4) both focusing and defocusing propagations possible.

Scattering-initiated parametric noise in optical parametric chirped-pulse amplification

peng yuan, Jing Wang, Jingui Ma, Daolong Tang, Binjie Zhou, Guoqiang Xie, and Liejia Qian

Doc ID: 240951 Received 14 May 2015; Accepted 29 Jun 2015; Posted 30 Jun 2015  View: PDF

Abstract: We experimentally study a new kind of parametric noise that is initiated from signal scattering and enhanced through optical parametric amplification. Such scattering-initiated parametric noise behaves similarly to parametric super-fluorescence in the spatial domain, yet is typically much stronger. In the time domain, it inherits the chirp of signal pulses and can be well compressed. We demonstrate that scattering-initiated parametric noise has little influ-ence on the pulse contrast but can degrade the energy conversion efficiency substantially.

Mid-IR femtosecond frequency conversion by soliton-probe collision in phase-mismatched quadratic nonlinear crystals

Morten Bache, Xing Liu, Binbin Zhou, and Hairun Guo

Doc ID: 241572 Received 25 May 2015; Accepted 29 Jun 2015; Posted 30 Jun 2015  View: PDF

Abstract: We show numerically that ultrashort self-defocusing temporal solitons colliding with a weak pulsed probe in the near-IR can convert the probe to the mid-IR. A near-perfect conversion efficiency is possible for a high effective soliton order. The near-IR self-defocusing soliton can form in a quadratic nonlinear crystal (beta-barium borate) in the normal dispersion regime due to cascaded (phase-mismatched) second-harmonic generation, and the mid-IR converted wave is formed in the anomalous dispersion regime between λ=2.2-2.4 μm as a resonant dispersive wave. This process relies on non-degenerate four-wave mixing mediated by an effective negative cross-phase modulation term caused by cascaded soliton-probe sum-frequency generation.

Photonic Crystal Fiber Polarization Rotator Based on Topological Zeeman Effect

LEI CHEN, Weigang Zhang, Tieyi Yan, LI Wang, Biao Wang, Quan Zhou, Liyu Zhang, and Jonathan Sieg

Doc ID: 241739 Received 27 May 2015; Accepted 29 Jun 2015; Posted 30 Jun 2015  View: PDF

Abstract: A photonic crystal fiber polarization rotator (PR for short) is proposed based on the topological Zeeman effect. The proposed PR is achieved by permanently twisting a segment of six-fold symmetric photonic crystal fiber with a matched length, and under the optimized parameters the PR can offer an almost 100% polarization conversion ratio in the wavelength of 1.55 μm band (~200 nm bandwidth) and a compact length of about 157 μm based on the numerical simulation result of the full-vector finite-element method. The proposed in-line PCF PR can be easily fabricated based on state-of-art PCF manufacturing, and it is a potential inexpensive candidate in the application of modern communication systems.

An electro-absorption modulator with an asymmetric coupled triple quantum well for low-voltage operation

Byunghoon Na, Gun Wu Ju, Yong Chul Cho, Yong Hwa Park, Yong-Tak Lee, Hee Ju Choi, Chang Young Park, and Soo Kyung Lee

Doc ID: 237765 Received 14 Apr 2015; Accepted 28 Jun 2015; Posted 29 Jun 2015  View: PDF

Abstract: We present an electro-absorption modulator based on the enhanced electro-optic effect of an asymmetric coupled triple quantum well (ACTQW) to achieve a large transmittance difference at low driving voltage for high-definition (HD) 3D imaging applications. Our numerical calculations show that an ACTQW structure can provide significantly lower-voltage operation without degradation of the absorption coefficient change at the operating wavelength of 850 nm. The fabricated electro-absorption modulator (EAM) based on an ACTQW shows that the operating voltage can be reduced by nearly 50% compared with an EAM based on a conventional rectangular quantum well while achieving a large transmittance difference in excess of 50%, which is in good agreement with the numerical calculation results. These results suggest that using an EAM with an ACTQW is a promising approach for the realization of a high-resolution 3D imaging system.

A new branch-cut algorithm for optical phase unwrapping

Paulo Acioly Marques dos Santos, Marcos Eduardo de Oliveira, and Júlio Cesar de Souza

Doc ID: 239771 Received 28 Apr 2015; Accepted 27 Jun 2015; Posted 29 Jun 2015  View: PDF

Abstract: In this article a proposal to the problem of 2D-phase unwrapping based on theory of residues will be presented. Here, wrapped phase maps with shifted phase jumps are used to balance residue charges. With this approach, we seek to minimize the processing time and the residues connection, which is essential in the development of branch-cut algorithms. Finally, a phase unwrapping algorithm will be applied on these wrapped maps, generated by Fourier Transform profilometry, for obtaining three-dimensional profiles of objects illuminated by photorefractive moire-like patterns generated in an experiment of real time dynamic holography and by fringe patterns generated with a Michelson interferometer.

Two-frame tilt-shift error estimation and phase demodulation algorithm

Maciek Wielgus, Zofia Sunderland, and Krzysztof Patorski

Doc ID: 240679 Received 14 May 2015; Accepted 27 Jun 2015; Posted 29 Jun 2015  View: PDF

Abstract: We present an algorithm capable of performing fringe pattern phase demodulation from two frames with unknown, linearly nonuniform phase shift, i.e., under presence of the tilt-shift error. The method consists of intensity based filtration of the tilt-shift component and subsequent two steps of a nonlinear error functional minimization. We verify the algorithm performance and robustness using both simulated and experimental data, indicating high accuracy of the presented method and its good numerical properties. Both small and large tilts can be treated. The paper is complimented with numerical codes and figures reproduction instruction, available online at http://goo.gl/h2h4AI.

Spectral and spatial resolving of photoelectric property of femtosecond laser drilled holes of GaSb1-xBix

Fangxing Zha, Chenbo Pan, Yuxin Song, Shumin Wang, Ye Dai, Jun Shao, Junyi Ye, and Xiren Chen

Doc ID: 237983 Received 15 Apr 2015; Accepted 26 Jun 2015; Posted 26 Jun 2015  View: PDF

Abstract: Femtosecond laser drilled holes of GaSbBi were characterized by the joint measurements of photoconductivity (PC) spectroscopy and laser beam induced current (LBIC) mapping. The excitation light in PC was focused down to 60 μm presenting the spectral information of local electronic property of individual holes. A redshift of energy band edge of about 6~8 meV was observed by the PC measurement when the excitation light irradiated on the laser drilled holes. The spatial resolving of photoelectric property was achieved by the LBIC mapping by which the observed “pseudo-holes” have much larger dimension than the geometric sizes of the holes. The reduced LBIC current with the pseudo-holes is associated with the redshift effect indicating that the electronic property of the holes rims have been modified by the femtosecond laser drilling.

A three-dimensional fiber probe based on micro focal-length collimation and fiber Bragg grating for the measurement of micro parts

Jiwen Cui, Junying Li, Kunpeng Feng, and Jiubin Tan

Doc ID: 240277 Received 05 May 2015; Accepted 26 Jun 2015; Posted 26 Jun 2015  View: PDF

Abstract: A three-dimensional (3D) fiber probe is proposed for the measurement of micro parts. The probe is made of fiber Bragg grating (FBG) which acts as micro focal-length cylindrical lens (MFLC-lens) of two mutually orthogonal micro focal-length collimation (MFL-collimation) optical paths. The radial displacement of the probe tip is transformed into the shift of the fringe image collimated by the MFL-collimation optical path; the axial displacement of the probe tip is transformed into the power ratio variation caused by the Bragg wavelength shift. Advantages of the probe are high precision, low cost, high measurable aspect ratio and capability of decoupling the 3D tactility.

Volumetric display with holographic parallel optical access and multilayer fluorescent screen

Kota Kumagai, Yoshio Hayasaki, Satoshi Hasegawa, and Suzuki Daichi

Doc ID: 237876 Received 09 Apr 2015; Accepted 25 Jun 2015; Posted 26 Jun 2015  View: PDF

Abstract: We propose a volumetric display based on holographic parallel optical access and two-photon excitation using a computer-generated hologram displayed on a liquid crystal spatial light modulator and a multilayer fluorescent screen. The holographic parallel optical access increased the number of voxels of the volumetric image per unit time. This approach increased the total input energy to the volumetric display, that is, the total fluorescence power, because the maximum energy incident at a point in the multilayer fluorescent screen is limited by the damage threshold. The multilayer fluorescent screen was newly developed to display colored voxels. The thin layer construction of the multilayer fluorescent screen minimized the axial length of the voxels. A volumetric display with only blue-green voxels and a volumetric display with both blue-green and red voxels were demonstrated.

Generation of Kerr combs centered at 4.5 μm in crystalline microresonators pumped by quantum-cascade lasers

Andrey Matsko, Anatoliy Savchenkov, Vladimir Ilchenko, Lute Maleki, Fabio Di Teodoro, Paul Belden, and William Lotshaw

Doc ID: 241922 Received 28 May 2015; Accepted 24 Jun 2015; Posted 26 Jun 2015  View: PDF

Abstract: We report on the generation of mid-infrared Kerr frequency combs in high-finesse CaF₂and MgF₂ whispering-gallery mode resonators pumped with continuous wave room temperature quantum cascade lasers. The combs were centered at 4.5μm, the longest wavelength to date. A frequency comb wider than a half of an octave was demonstrated when approximately 20mW of pump power was coupled to an MgF₂ resonator characterized with quality factor exceeding 10⁸.

Three-Dimensional Sparse Image Reconstruction for Terahertz Surface Layer Holography with Random Step Frequency

Chao Li, Wei Liu, Zhaoyang Sun, Qunying Zhang, and Guangyou Fang

Doc ID: 242786 Received 11 Jun 2015; Accepted 24 Jun 2015; Posted 26 Jun 2015  View: PDF

Abstract: In this Letter, a sparse image reconstruction approach is proposed for three-dimensional (3D) terahertz (THz) surface layer holography by a sharply dwindled amount of frequency samples, without reducing the high quality of the final reconstructed 3D THz images. To avoid the range ambiguity resulted from the reduction of frequency samples, a random step frequency method is adopted to evaluate the rough range profile of the 3D surface layer. With the obtained range profile, a de-ambiguity procedure is proposed to demodulate the sparse echoed data to greatly compress the maximum nonambiguous range and recover all the information for 3D holography image reconstruction. Proof-of-state experiments are performed in 0.2 THz band. The results verify the effectiveness and the efficiency of the sparse imaging scheme for THz surface layer 3D holography.

Valley-dependent beams controlled by pseudomagnetic field in a distorted photonic graphene

Hai Tao Jiang, Fusheng Deng, Yunmei Li, yong sun, Xiao Wang, Zhiwei Guo, Yunlong Shi, Kai Chang, and Hong Chen

Doc ID: 243029 Received 15 Jun 2015; Accepted 24 Jun 2015; Posted 26 Jun 2015  View: PDF

Abstract: The generation and control of valley pseudospin currents are the core of valleytronics. Here, the photonic analogy for generation and control of valley pseudospin currents using the pseudomagnetic fields induced in a strained graphene is investigated in microwave regime. In a photonic graphene with a uniaxial distortion, photons in two different valleys experience pseudomagnetic fields with opposite signs and valley-dependent propagations in bended paths are observed. The external-field-free photonic transportation behavior might be very useful in controlling the flow of light in future valley polarized devices.

Field of view for near-field aperture synthesis imaging

David Buscher

Doc ID: 239898 Received 29 Apr 2015; Accepted 24 Jun 2015; Posted 29 Jun 2015  View: PDF

Abstract: Aperture synthesis techniques are increasingly being employed to provide high angular resolution images in situations where the object of interest is in the near field of the interferometric array. Previous work has showed that an aperture synthesis array can be refocused on an object in the near field of an array, provided that the object is smaller than the effective Fresnel zone size corresponding to the array-object range. We show here that, under paraxial conditions, standard interferometric techniques can be used to image objects which are substantially larger than this limit. We also note that interferometric self-calibration and phase-closure image reconstruction techniques can be used to achieve near-field refocussing without requiring accurate object range information. We use our results to show that the field of view for high-resolution aperture synthesis imaging of geosynchronous satellites from the ground can be considerably larger than the largest satellites in Earth orbit.

High Purcell factor in fiber Bragg gratings utilizing the fundamental slow-light mode

George Skolianos, Arushi Arora, Martin Bernier, and Michel Digonnet

Doc ID: 241246 Received 19 May 2015; Accepted 24 Jun 2015; Posted 30 Jun 2015  View: PDF

Abstract: We demonstrate through numerical simulations that the slow-light resonances that exist in strong apodized fiber Bragg gratings (FBGs) fabricated with femtosecond pulses in deuterium-loaded fibers can exhibit very large intensity enhancements and Purcell factors with proper optimization of their length. This potential is illustrated with two saturated FBGs less than 5 mm long, annealed to reduce their internal loss. The first one exhibits the largest measured Purcell factor in an all-fiber device (38.7), and the second one the largest intensity enhancement (1525). These devices are anticipated to have significant applications in quantum-dot lasers, nonlinear fiber devices, and cavity quantum-electrodynamics experiments.

On-chip microwave signal generation based on a silicon micro-ring modulator

Haifeng Shao, hui Yu, Xia Li, Yan Li, Huan Wei, Tingge Dai, Jianyi Yang, Xiaoqing Jiang, Gencheng Wang, Jianfei Jiang, and Qimei Chen

Doc ID: 237915 Received 15 Apr 2015; Accepted 24 Jun 2015; Posted 25 Jun 2015  View: PDF

Abstract: A photonic-assisted microwave signal generator is demonstrated based on a silicon micro-ring modulator. The micro-ring cavity incorporates an embedded PN junction which enables a microwave signal to modulate the lightwave circling inside. The DC component of the modulated light is trapped in the cavity, while the high-order sideband components are able to exit the cavity and then generate microwave signals at new frequencies in a photodetector. In our proof-of-concept experiment, a 10 GHz microwave signal is converted to a 20 GHz signal in the optical domain with an electrical harmonic suppression ratio of above 20 dB. An analytic model is also established to explain the operation mechanism, which agrees well with the measured data.

Adaptive mode control based on a Fiber Bragg grating

Yong Xu, Peng Lu, Anbo Wang, and Shay Soker

Doc ID: 238173 Received 15 Apr 2015; Accepted 24 Jun 2015; Posted 25 Jun 2015  View: PDF

Abstract: We experimentally demonstrated adaptive control of linearly polarized modes in a two-mode fiber. Our method is based on a stepwise adaptive optics algorithm, with feedback determined by the relative magnitude of optical power reflected by a fiber Bragg grating and the transmitted power. Combining this method with time-division-multiplexing, it should be possible to adaptively control guided modes at any desired location within a few-mode fiber network.

An On-Chip Optical Lattice for Cold Atom Experiments

Dana Anderson, Cameron Straatsma, Megan Ivory, Janet Duggan, Jaime Ramirez-Serrano, and Evan Salim

Doc ID: 240877 Received 21 May 2015; Accepted 24 Jun 2015; Posted 25 Jun 2015  View: PDF

Abstract: An atom-chip-based integrated optical lattice system for cold and ultracold atom applications is presented. The retro-reflection optics necessary for forming the lattice are bonded directly to the atom chip, enabling a compact and robust on-chip optical lattice system. After achieving Bose-Einstein condensation in a magnetic chip trap, we load atoms directly into a vertically oriented 1D optical lattice and demonstrate Landau-Zener tunneling. The atom chip technology presented here can be readily extended to higher dimensional optical lattices.

200 kHz 5.5W Yb3+:YVO4-based chirped pulse regenerative amplifier

Viktor Kisel, Alexander Rudenkov, Nikolai Kuleshov, and Vladimir Matrosov

Doc ID: 241745 Received 26 May 2015; Accepted 24 Jun 2015; Posted 25 Jun 2015  View: PDF

Abstract: Chirped pulse regenerative amplifier based on Yb:YVO4 (Yb:YVO) crystal was demonstrated for the first time to our knowledge. A novel wavelength-independent off-axis technique was used to deliver 26.6 W of pump power with low quantum defect. Seeded by means of a 120 fs Yb:YVO4 oscillator, it generates as much as 5.5 W of average output power with chirped pulses and 4.2 W with 200 fs compressed pulses at 200 kHz repetition rate. Maximum pulse energy of 140 µJ was obtained at pulse repetition frequencies up to 25 kHz at the central wavelength of 1018 nm.

Ultrafast properties of femtosecond-laser-ablated GaAs and its application to terahertz optoelectronics

Julien Madeo, Athanasios Margiolakis, Zhenyu ZHAO, Peter Hale, Michael Man, Quanzhong Zhao, Wei Peng, wangzhou Shi, and Keshav Dani

Doc ID: 241582 Received 28 May 2015; Accepted 23 Jun 2015; Posted 25 Jun 2015  View: PDF

Abstract: We report on the first terahertz emitter based on femtosecond-laser-ablated GaAs, demonstrating a 65% enhancement in THz emission at high optical power compared to the non-ablated device. Counter-intuitively, the ablated device shows significantly lower photocurrent and carrier mobility. We understand this behavior in terms of n-doping, shorter carrier lifetime and enhanced photoabsorption arising from the ablation process. Our results show that laser-ablation allows for efficient and cost-effective optoelectronic terahertz devices, via the manipulation of fundamental properties of materials.

Hydrogen alpha laser-ablation plasma diagnostics

Christian Parigger, David Surmick, Ghaneshwar Gautam, and Ashraf EL Sherbini

Doc ID: 240079 Received 01 May 2015; Accepted 23 Jun 2015; Posted 25 Jun 2015  View: PDF

Abstract: Spectral measurements of the Hα Balmer series line and the absolute continuum radiation are applied to draw inferences of electron density, temperature, and the level of self-absorption in laser-ablation of a solid ice target in ambient air. Electron densities of 17 to 3.2 × 10²⁴/m³ are determined from absolute-calibrated emission coefficients for time delays of 100 ns to 650 ns after generation of laser plasma using Q-switched Nd:YAG radiation. The corresponding temperatures of 4.5 to 0.95 eV were evaluated from the absolute spectral radiance of the continuum at the longer wavelengths. The red-shifted, Stark-broadened hydrogen alpha line emerges from the continuum radiation after a time delay of 300 ns. The inferred electron densities from Hα line-shape analysis agree with the values obtained from the plasma emission coefficients.

>200W incoherently combined supercontinuum source using a 3×1 broadband fiber power combiner

Zilun Chen, Hang Zhou, Aijun Jin, Xuanfeng Zhou, Bin Zhang, Sheng-Ping Chen, Jing Hou, and Jinbao Chen

Doc ID: 237223 Received 31 Mar 2015; Accepted 23 Jun 2015; Posted 25 Jun 2015  View: PDF

Abstract: We report an incoherently combined near-infrared SC source with >200 W output power using a 3×1 broadband fiber power combiner. A broadband fiber power combiner is designed and theoretically investigated. The power transmission efficiencies of light at different wavelengths of the combiner are calculated and the combiner is verified to be capable of combining broadband sources efficiently. Then a combiner is fabricated. Three ~70 W near infrared SC sources are constructed and then using the combiner a >200 W near infrared SC source is obtained. Conclusively, using incoherently combining method we can obtain a high power SC source and the thermo-management can be realized easily. We believe that this is a suitable method to obtain higher power SC source.

Ultra Hybrid Plasmonics: Strong Coupling of Plexcitons with Plasmon Polaritons

SINAN BALCI and Coskun Kocabas

Doc ID: 243135 Received 19 Jun 2015; Accepted 22 Jun 2015; Posted 25 Jun 2015  View: PDF

Abstract: We report a ternary coupled plasmonic system consisting of excitons of J-agregated cyanine dye, localized surface plasmon polaritons of Ag nanoparticles, and propagating surface plasmon polaritons of continuous Ag thin film. J-aggregate dyes are uniformly self-assembled on colloidally synthesized Ag nanoprisms forming plexcitonic nanoparticles which are placed nanometers distance away from the Ag thin film. The polarization dependent reflection measurements, corroborated by the theoretical predictions, reveal that the strong coupling of plasmon polaritons and plexcitons results in a newly formed plasmon-exciton-plasmon hybridized state we called it here, for the first time, as plexcimon state. The ternary hybrid plasmonic system shows a coupled resonator optical waveguide (CROW) like dispersion characteristics. The group velocity of the plexcimon state approaches zero at the band edges. The ultra hybrid plasmonic system presented here is promising for a variety of light-matter interaction studies including polariton lasers, plasmonic devices, plasmonic waveguiding, and spectroscopy.

Snap-shot hyperspectral imaging of vascular dynamics in a mouse window chamber model

Hansford Hendargo, Yulin Zhao, Taylor Allenby, and Gregory Palmer

Doc ID: 238480 Received 20 Apr 2015; Accepted 22 Jun 2015; Posted 24 Jun 2015  View: PDF

Abstract: Understanding tumor vascular dynamics through parameters such as blood flow and oxygenation can yield insight into tumor biology and therapeutic response. Hyperspectral microscopy enables optical detection of hemoglobin saturation or blood velocity by either acquiring multiple images that are spectrally distinct or by rapid acquisition at a single wavelength over time. However, the serial acquisition of spectral images over time prevents the ability to monitor rapid changes in vascular dynamics and cannot monitor concurrent changes in oxygenation and flow rate. Here, we introduce snap shot-hyperspectral imaging (SS-HSI) for use in imaging the microvasculature in mouse dorsal window chambers. By spatially multiplexing spectral information into a single image capture, simultaneous acquisition of dynamic hemoglobin saturation and blood flow over time is achieved down to the capillary level and provides an improved optical tool for monitoring rapid in vivo vascular dynamics.

Phase noise mitigation of QPSK signal utilizing phase-locked multiplexing of signal harmonics and amplitude saturation

Amirhossein Mohajerin Ariaei, Morteza Ziyadi, Mohammad Reza Chitgarha, ahmed almaiman, Yinwen Cao, Bishara Shamee, Jeng-Yuan Yang, Youichi Akasaka, Motoyoshi Sekiya, Shigehiro Takasaka, Ryuichi Sugizaki, Joseph Touch, Moshe Tur, Carsten Langrock, Martin Fejer, and Alan Willner

Doc ID: 239813 Received 27 Apr 2015; Accepted 22 Jun 2015; Posted 24 Jun 2015  View: PDF

Abstract: We demonstrate an all-optical phase noise mitigation scheme based on the generation, delay, and coherent summation of higher-order signal harmonics. The signal, its third-order harmonic, and their corresponding delayed variant conjugates create a staircase phase transfer function that quantizes the phase of QPSK signal to mitigate phase noise. The signal and the harmonics are automatically phase-locked multiplexed, avoiding the need for phase-based feedback loop and injection locking to maintain coherency. The residual phase noise converts to amplitude noise in the quantizer stage, which is suppressed by parametric amplification operated in the saturation regime. Phase noise reduction of ~40% and OSNR-gain of ~3dB at BER 10-3 are experimentally demonstrated for 20 and 30 Gbaud QPSK input signals.

Rigorous simulations of coupling between core and cladding modes in a double helix fiber

Maciej Napiórkowski and Waclaw Urbanczyk

Doc ID: 239995 Received 30 Apr 2015; Accepted 22 Jun 2015; Posted 24 Jun 2015  View: PDF

Abstract: Using a fully vectorial numerical method based on the transformation optics formalism, we analyzed the effect of resonant coupling between core and cladding modes in twisted elliptical core fibers. Our rigorous simulations revealed the existence of a much more rich resonance spectrum than that predicted by simplified perturbation approaches. This effect is caused by the appearance of even harmonics in the angular field distribution of higher order cladding modes due to their interaction with the fiber core of twofold symmetry. We also analyzed the dependence of the polarization state of the core modes upon a twist rate and wavelength. We demonstrated the effect of resonant polarization perturbation of the core modes, especially well visible for the couplings between circularly polarized core modes and cladding modes of opposite handedness.

A 20-Gbps optical LiFi transport system

Hai-Han Lu, Cheng-Ling Ying, Chung-Yi Li, Jun-Ren Zheng, Peng-Chun Peng, and Wen-Jeng Ho

Doc ID: 240099 Received 30 Apr 2015; Accepted 22 Jun 2015; Posted 24 Jun 2015  View: PDF

Abstract: A 20-Gbps optical light-based WiFi (LiFi) transport system employing vertical cavity surface emitting laser (VCSEL) and external light injection technique with 16-quadrature amplitude modulation (QAM)-orthogonal frequency-division multiplexing (OFDM) modulating signal is proposed. God bit error rate (BER) performance and clear constellation map are achieved in our proposed optical LiFi transport systems. An optical LiFi transport system, delivering 16-QAM-OFDM signal over a 6-m free-space link, with a data rate of 20 Gbps is successfully demonstrated. Such a 20-Gbps optical LiFi transport system provides the advantage of a free-space communication link for high data rates, which can accelerate the visible laser light communication (VLLC) deployment.

Physically-meaningful depolarization metric based on the differential Mueller matrix

Noé Ortega-Quijano, Jose Arce-Diego, and Felix Fanjul-Velez

Doc ID: 240985 Received 14 May 2015; Accepted 22 Jun 2015; Posted 24 Jun 2015  View: PDF

Abstract: We present a novel depolarization metric for Mueller matrices based on the differential Mueller formalism. The proposed metric relies on the statistical interpretation of the differential Mueller matrix. We show that the differential depolarization index succesfully quantifies depolarization even when applied to specific types of Mueller matrices for which some widely-used depolarization metrics yield erroneous results. Moreover, the fact that the presented metric is directly linked to the variances and covariances of the elementary anisotropic properties of the sample makes it a valuable tool to quantify depolarization on a physically meaningful basis.

The Fresnel transform as a projection onto a Nijboer-Zernike basis set

Yang Wu, Damien Kelly, Stefan Sinzinger, Matthias Hillenbrand, and Liang Zhao

Doc ID: 236642 Received 24 Mar 2015; Accepted 22 Jun 2015; Posted 24 Jun 2015  View: PDF

Abstract: The Fresnel transform is widely used in optics to calculate the free space propagation of paraxial fields. Generally there is no analytical solution for the Fresnel transform, therefore the numerical methods are often used. In this manuscript we propose a new semi-analytical method to calculate the Fresnel transform, which is based on Extended Nijboer Zernike theory. We calculate two examples to investigate how the sampling rate and maximal number of Zernike polynomials affect the accuracy of our results, and then use this method to calculate the reconstruction of two different kinds of holograms. At the end, we discuss the advantages and disadvantages of our method.

Shaping Field for Deep Tissue Microscopy

Hyungsik Lim and Jorge Colon

Doc ID: 237675 Received 07 Apr 2015; Accepted 22 Jun 2015; Posted 24 Jun 2015  View: PDF

Abstract: Imaging deep tissue can be extremely inefficient when the region of interest has a non-planar morphology buried in a thick sample, yielding a severely limited field of view (FOV). Here we describe a novel microscopic technique, namely adaptive field microscopy, which enhances the FOV by dynamic control of the image plane. The conformation of the image plane is continuously adjusted in situ to match the oblique orientation or curvature of the sample. The practicality is demonstrated for ophthalmic imaging, where a large area of the corneal epithelium of intact mouse eye is captured in a single FOV with subcellular resolution.

Ultra-high Q Thin Silicon Nitride Strip-Loaded Ring Resonators

Mher Ghulinyan, Lucio Stefan, Martino Bernard, Romain Guider, Georg Pucker, and Lorenzo Pavesi

Doc ID: 240632 Received 11 May 2015; Accepted 21 Jun 2015; Posted 24 Jun 2015  View: PDF

Abstract: We report on the design, fabrication and characterization of thin $\mathrm{Si_{3}N_{4}}$ ultra-high quality (UHQ) factor ring resonators monolithically integrated on a silicon chip. The devices are based on a strip-loaded configuration and operate at both near-infrared (NIR) and third telecom wavelengths. This approach allows us to use a guiding $\mathrm{Si_{3}N_{4}}$ core which is one order of magnitude thinner than what has been reported in past for obtaining similar device performances. Our strip loaded devices take benefit from the absence of physically etched lateral boundaries to show minute light scattering and, therefore, reducing significantly scattering-related losses. Consequently, UHQ's of $3.7 \times 10^6$ in the NIR and high quality factors of up to $9 \times 10^5$ in the C-band were measured for the guiding material thickness of 80~nm and 115~nm, respectively. These first results are subject to further improvements which may allow to employ strip-loaded resonators in nonlinear frequency conversion or quantum computing schemes within the desired spectral range provided by the material transparency.

Ultra-broadband terahertz pulses generated in the organic crystal DSTMS

Klaus Reimann, Carmine Somma, Giulia Folpini, Jyotsana Gupta, Michael Woerner, and Thomas Elsaesser

Doc ID: 240967 Received 14 May 2015; Accepted 21 Jun 2015; Posted 24 Jun 2015  View: PDF

Abstract: Electric field transients covering the extremely wide frequency range from 0.5 to 26 THz are generated in the organic nonlinear crystal 4-N,N-dimethylamino-4'-N'-methylstilbazolium 2,4,6-trimethylbenzenesulfonate (DSTMS). Parametric difference frequency mixing within the spectrum of 25 fs amplified pulses centered at 800 nm provides a highly stable broadband output with an electric field amplitude of up to several hundred kilovolts/cm. The high stability of the terahertz pulse parameters allows for sensitive phase-resolved broadband spectroscopy of optically thick crystalline samples.

Three-dimensional mapping of fluorescent nanoparticles using incoherent digital holography

Yoshio Hayasaki, Ryosuke Abe, and Takumi Yanagawa

Doc ID: 240146 Received 01 May 2015; Accepted 20 Jun 2015; Posted 24 Jun 2015  View: PDF

Abstract: Three-dimensional mapping of fluorescent nanoparticles was performed by using incoherent digital holography. The positions of the nanoparticles were quantitatively determined by using Gaussian fitting of the axial and lateral diffraction distributions through position calibration from the observation space to the sample space. It was found that the axial magnification was constant whereas the lateral magnification linearly depended on the axial position of the fluorescent nanoparticles. The mapping of multiple fluorescent nanoparticles fixed in gelatin and a single fluorescent nanoparticle manipulated with optical tweezers in water was demonstrated.

Dense WDM Transmission at 2 µm enabled by an Arrayed Waveguide Grating

Hongyu Zhang, Mickael Gleeson, Nan Ye, Nicola Pavarelli, Xing Ouyang, Jian Zhao, Niamh Kavanagh, Cedric Robert, Hua Yang, Padraic Morrissey, kevin thomas, agnieszka gocalinska, Yong Chen, Tom Bradley, John Wooler, John Hayes, Eric Rodrigue Numkam Fokoua, Zhihong Li, Shaif-ul Alam, Francesco Poletti, Marco Petrovich, David Richardson, Brian Kelly, John O'Carroll, Richard Phelan, Emanuele Pelucchi, Peter O'Brien, Frank Peters, Brian Corbett, and Fatima Garcia Gunning

Doc ID: 239905 Received 28 Apr 2015; Accepted 20 Jun 2015; Posted 24 Jun 2015  View: PDF

Abstract: We show, for the first time, dense WDM (8× 20 Gbit/s) transmission at 2 μm enabled by advanced modulation formats (4-ASK Fast-OFDM) and the development of key components, including a new arrayed waveguide grating (AWGr) at 2 μm. The AWGr shows -12.8 ±1.78 dB of excess loss with an 18-dB extinction ratio and a thermal tunability of 0.108 nm/ºC.

Bouncing of a dispersive wave in a solitonic cage

Alexandre Kudlinski, Shaofei Wang, Arnaud Mussot, Matteo Conforti, and Xianglong Zeng

Doc ID: 241887 Received 28 May 2015; Accepted 20 Jun 2015; Posted 25 Jun 2015  View: PDF

Abstract: We report the experimental observation of a weak dispersive wave trapping within a cage formed by two solitons in an optical fiber. We show that the dispersive wave bouncing is accompanied by a back and forth wavelength conversion of the probe to an idler wave. Besides, we observed the destruction of the soliton cage when dispersive wave power is increased, leading to the collision of the solitons.

Pre-resonance Stimulated Raman Scattering for Water Bilayer Structure on Laser-Induced Plasma Bubble Surface

zhiwei men, zhanlong li, Li Dong, wenhui fang, chenglin sun, shenghan Wang, and zuowei li

Doc ID: 241036 Received 15 May 2015; Accepted 19 Jun 2015; Posted 24 Jun 2015  View: PDF

Abstract: Pre-resonance stimulated Raman scattering (PSRS) from water molecules at the air/water interfacial regions was studied when the laser-induced plasma bubble was generated at the interfaces. A characteristically lower Raman shift of OH stretching vibrational modes of water molecules at around 3000 cm−1 (370 meV) was observed, in which the mechanisms were possibly attributed to the strong hydrogen bond in well-ordered water bilayer structure that was formed on laser-induced plasma bubble surface. Simultaneously, the PSRS of ice Ih at about 3100 cm−1 was obtained, which also belonged to the strong hydrogen bond effect in ice Ih structure.

Integrated Quasi-Phase-Matched Second-Harmonic Generator and Electro-Optic Phase Modulator for Low-noise Phase-sensitive Amplification

Koji Enbutsu, Osamu Tadanaga, Takeshi Umeki, Masaki Asobe, and Hirokazu Takenouchi

Doc ID: 238436 Received 22 Apr 2015; Accepted 19 Jun 2015; Posted 24 Jun 2015  View: PDF

Abstract: We propose a quasi-phase-matched second-harmonic generator integrated with an electro-optic (EO) phase modulator into a directly-bonded LiNbO3 (DB-LN) waveguide to obtain high-SNR pump-light for a phase-sensitive amplifier (PSA). This integrated device exhibited 1-MHz modulation and 1-W second-harmonic-generation properties sufficient for phase-locking between the signal and pump, and PSA gain, respectively. A novel PSA configuration based on the high-input-power-tolerance of the device helps to suppress the noise from the erbium-doped fiber amplifier used for pump-light generation and led to an improvement of the signal-to-noise ratio (SNR) of the pump-light. The SNR improvement was confirmed by comparing the noise figures of PSAs employing the DB-LN waveguide and Ti-diffused LN waveguide modulator.

Optical Constants of InxGa1-xN (0≤x≤0.73) in the Visible and Near-Infrared Wavelength Regimes

Arnab Hazari, Aniruddha Bhattacharya, Thomas Frost, Songrui Zhao, Md Zunaid Baten, Zetian Mi, and Pallab Bhattacharya

Doc ID: 236672 Received 24 Mar 2015; Accepted 19 Jun 2015; Posted 24 Jun 2015  View: PDF

Abstract: The complex refractive indices of InxGa1-xN epitaxial layers have been determined from analysis of data obtained by spectroscopic ellipsometry. The measurements were made in the wavelength range of 400 to 1687nm. The samples were grown by plasma-assisted molecular beam epitaxy on (001) silicon substrate and are of the wurtzite crystalline form. A comparison of the fundamental absorption edge derived from analysis of measured data and the measured photoluminescence peak emission energy indicates a Stokes shift to be present in the alloys.

Modeling of spectral changes in bent fiber Bragg gratings

Wei Zhang, Xiaohua Lei, Weimin Chen, Hengyi Xu, and Anbo Wang

Doc ID: 240125 Received 01 May 2015; Accepted 18 Jun 2015; Posted 19 Jun 2015  View: PDF

Abstract: To better apply fiber Bragg gratings (FBGs) to various bending required situations, well understanding of their bending characteristics is crucial. In this letter, a theoretical model to describe the changes of spectral properties of an FBG against the bending radius is proposed. This model shows that all the bend-induced spectral changes, the shift of center wavelength, decrease of reflectivity and reduction of bandwidth, may be explained by the decrease of the effective “dc” refractive index change spatially averaged over one grating period. Experimental results are in agreement with theoretical predictions and confirm the effectiveness of the proposed model.

Speckle-based Spectrometer

Steen Hanson, Michael Jakobsen, and Maumita Chakrabarti

Doc ID: 238309 Received 17 Apr 2015; Accepted 17 Jun 2015; Posted 19 Jun 2015  View: PDF

Abstract: A novel spectrometer concept is analyzed and experimentally verified. The method relies on probing the speckle displacement due to a change in the incident wavelength. A rough surface is illuminated at an oblique angle and the peak position of the covariance between the speckle patterns observed in the far field with the two wavelengths reveals the wavelength change. A spectral resolution of 100 Mhz is shown to be achievable.

167.75 nm vacuum-ultraviolet ps laser by eighth-harmonic generation of a 1342 nm Nd:YVO₄ amplifier in KBBF

ZONG Nan, Dai shibo, Feng Yang, Shenjin Zhang, zhimin wang, Fengfeng Zhang, Wei Tu, Linqiao Shang, lijuan Liu, Xiao Wang, Jin-Yuan Zhang, Da Cui, Qinjun Peng, Rukang Li, Chuang Chen, and Zuyan Xu

Doc ID: 238335 Received 17 Apr 2015; Accepted 17 Jun 2015; Posted 19 Jun 2015  View: PDF

Abstract: We demonstrate a high power ps 167.75 nm vacuum-ultraviolet (VUV) laser by cascaded second-harmonic generation (SHG). The VUV laser is produced by eighth-harmonic generation (EHG) of a mode-locked ps 1342 nm Nd:YVO₄ amplifier through three stages cascaded SHG with two LiB₃O₅ crystals and one KBe₂BO₃F₂ crystal, successively. The 167.75 nm laser provides up to 65 μW output power, the corresponding photon flux and photon flux density are 5.5×10¹³ photons/s and 1.6×10¹⁸ photons/(s•cm²), respectively. To our best knowledge, this is the shortest VUV wavelength ever generated through cascaded SHG method and the highest average power of all-solid-state lasers below 170 nm. Such a high power, high photon flux density ps laser at 167.75 nm is of great interest for VUV laser-based photoemission spectroscopy.

Silica-based fiber Raman laser at > 2.4 μm

Yan Feng, Lei Zhang, and Huawei Jiang

Doc ID: 239618 Received 23 Apr 2015; Accepted 16 Jun 2015; Posted 19 Jun 2015  View: PDF

Abstract: Raman laser generation at the long wavelength transmission edge of silica fiber is explored. Numerical simulation reveals that high efficiency 2nd Stokes Raman laser operation around 2.5 μm is feasible with highly Ge-doped silica fiber as gain medium and pulsed 2 μm fiber laser as pump source. Based on spontaneous cascaded Raman amplification process, 0.30 W laser at 2.43 μm is obtained with an optical efficiency of 16.5% pumped at 2008 nm. And 0.15 W laser at 2.48 μm is achieved with an optical efficiency of 7.9 % pumped at 2040 nm. To the best of our knowledge, the results represent the longest wavelength operation of silica based fiber laser.

Three-dimensional motion detection of a 20 nm gold nanoparticle using twilight-field digital holography with coherence regulation

Kazufumi Goto and Yoshio Hayasaki

Doc ID: 239711 Received 29 Apr 2015; Accepted 16 Jun 2015; Posted 19 Jun 2015  View: PDF

Abstract: In the twilight-field method for obtaining interference fringes with high contrast in in-line digital holography, only the intensity of the reference light is regulated to be close to the intensity of the object light, which is the ultra-weak scattered light from a nanoparticle, by using a low-frequency attenuation filter. Coherence of the light also strongly affects the contrast of the interference fringes. High coherence causes a lot of undesired coherent noise, which masks the fringes derived from the nanoparticles. Too-low coherence results in fringes with low contrast and a correspondingly low signal-to-noise ratio. Consequently, proper regulation of the coherence of the light source, in this study the spectral width, improves the minimum detectable size in holographic three-dimensional position measurement of nanoparticles. By using these methods, we were able to measure the position of a gold nanoparticle with a minimum diameter of 20 nm.

Fabrication of binary volumetric diffractive optical elements in photosensitive chalcogenide AMTIR-1 layers

Alexandre Joerg and Julien Lumeau

Doc ID: 239908 Received 30 Apr 2015; Accepted 15 Jun 2015; Posted 16 Jun 2015  View: PDF

Abstract: Recording of binary volumetric diffractive optical elements within a 13 µm thick photosensitive chalcogenide layer using an innovative exposure set-up based on digital micro-mirrors devices is demonstrated. Different examples of beam transformations are shown such as the conversion of Gaussian beam into higher order modes or top-hat beam shapers.

Dark-field full-field optical coherence tomography

Egidijus Auksorius and Claude Boccara

Doc ID: 240800 Received 12 May 2015; Accepted 14 Jun 2015; Posted 19 Jun 2015  View: PDF

Abstract: Full-field optical coherence tomography (FF-OCT) provides en face images from deep in tissue with high spatial resolution. However, specular reflections that come from flat interfaces can be stronger than the backscattered signal from a specimen by many orders of magnitude, which may reduce image contrast, in particular close to flat interfaces, and furthermore, limit available imaging depth. To this end, we demonstrate dark-field FF-OCT (d-FF-OCT) that enables blocking specular reflections by putting an opaque disk in the pupil-conjugated plane and by replacing the reference mirror with a blazed reflective diffraction grating. The grating is used to eliminate a walk-off between the sample and tilted reference beams on a camera that otherwise limits the imaging field-of-view (FOV). We show that d-FF-OCT can efficiently suppress specular reflections from the glass-tissue interface by at least two orders of magnitude and yield higher contrast images compared to the conventional FF-OCT.

Optimization for high-energy and high-efficiency broadband optical parametric chirped-pulse amplification in LBO near 800 nm

Xiaoyan Liang, Lianghong Yu, Lu Xu, Li Wenqi, Chun Peng, Zhanggui Hu, Cheng Wang, Xiaoming Lu, YuXi Chu, Biao Gan, Haihe Lu, Dingjun Yin, Yuxin Leng, Ruxin Li, Zhizhan Xu, Yanqi Liu, XinLiang Wang, and Liu Xiaodi

Doc ID: 236190 Received 17 Mar 2015; Accepted 14 Jun 2015; Posted 30 Jun 2015  View: PDF

Abstract: In this letter, we present a study of high-energy and high-conversion-efficiency broadband optical parametric chirped-pulse amplification (OPCPA) system with a 100 mm×100 mm×17 mm LBO crystal near 800 nm. The results showed that the back-conversion was sensitively affected by the intensity of the pump and the injected signal. It occurred when the injected signal was above 0.82 J with a pump energy of 170 J, and this effect also reshaped the amplified spectrum. After optimization, an amplified energy of 45.3 J was achieved with a conversion efficiency of 26.3% by the OPCPA. The peak power of the hybrid CPA-OPCPA laser system reached 1.02 PW with a compressed duration of 32 fs, which is the first reported OPCPA peak power higher than 1 PW, to the best of our knowledge.

Spectral Engineering with Coupled Microcavities: Active Control of Resonant Mode-Splitting

Mario Souza, Luis Barea, Guilherme de Rezende, Gustavo Wiederhecker, Newton Frateschi, and Antonio von Zuben

Doc ID: 240422 Received 28 May 2015; Accepted 13 Jun 2015; Posted 26 Jun 2015  View: PDF

Abstract: Optical mode-splitting is an efficient tool to shape and fine-tune the spectral response of resonant nanophotonic devices. The active control of mode-splitting, however, is either small or accompanied by undesired resonance shifts, often much larger than the resonance-splitting. We report a control mechanism that enables reconfigurable and widely tunable mode-splitting while efficiently mitigating undesired resonance shifts. This is achieved by actively controlling the excitation of counter-traveling modes in coupled resonators. The transition from a large splitting (80 GHz) to a single-notch resonance is demonstrated using low power microheaters (35 mW). We show that the spurious resonance-shift in our device is only limited by thermal crosstalk and resonance-shift-free splitting control may be achieved.

Chip-integrated nearly perfect absorber at telecom wavelengths by graphene coupled with nanobeam cavity

wei xu, Zhu Hong, Ken Liu, Jianfa Zhang, Xiaodong Yuan, Qisheng Lu, and Shiqiao Qin

Doc ID: 238193 Received 16 Apr 2015; Accepted 13 Jun 2015; Posted 15 Jun 2015  View: PDF

Abstract: We exploit the concept of critical coupling to graphene based chip-integrated applications and numerically demonstrate that chip-integrated nearly perfect graphene absorber at the wavelengths around 1.55 μm can be obtained by graphene nearly critical coupling with a nanobeam cavity. The key points are reducing the radiation loss and transmission possibly, and together with controlling the coupling rate of the cavity to the input waveguide to be equal to the absorption rate of graphene. Simulation results show that the absorption of monolayer graphene with a total length of only 4.4 μm is raised up to 96.08%. Our study may have potential applications in the chip-integrated photodetectors

Tunable RF Photonics Filter using a Comb-based Optical Tapped-Delay-Line with an Optical Nonlinear Multiplexer

Morteza Ziyadi, Amirhossein Mohajerin Ariaei, Mohammad Reza Chitgarha, Salman Khaleghi, ahmed almaiman, Yinwen Cao, Amin Abouzaid, Bishara Shamee, Moshe Tur, Loukas Paraschis, Carsten Langrock, Martin Fejer, Joseph Touch, and Alan Willner

Doc ID: 238360 Received 20 Apr 2015; Accepted 13 Jun 2015; Posted 15 Jun 2015  View: PDF

Abstract: An RF photonic filter is experimentally demonstrated using an optical tapped delay line based on an optical frequency comb and a PPLN waveguide as multiplexer. The approach is used to implement RF filters with variable bandwidth, shape and center-frequency.

In situ characterization of few-cycle laser pulses in transient absorption spectroscopy

Alexander Blättermann, Thomas Pfeifer, Christian Ott, Thomas Ding, Veit Stooß, Marc Rebholz, Martin Laux, and Andreas Kaldun

Doc ID: 239993 Received 06 May 2015; Accepted 09 Jun 2015; Posted 09 Jun 2015  View: PDF

Abstract: Attosecond transient absorption spectroscopy has thus far been lacking the capability to simultaneously characterize the intense laser pulses at work within a time-resolved quantum dynamics experiment. However, precise knowledge of these pulses is key to extracting quantitative information in strong-field highly nonlinear light-matter interactions. Here, we introduce and experimentally demonstrate an ultrafast metrology tool based on the time-delay-dependent phase shift imprinted on a strong-field driven resonance. Since we analyze the signature of the laser pulse interacting with the absorbing spectroscopy target, the laser pulse duration and intensity are determined in situ. As we also show, this approach allows for the quantification of time-dependent bound-state dynamics in one and the same experiment. In the future, such experimental data will facilitate more precise tests of strong-field dynamics theories.

Video rate two-photon excited fluorescence lifetime imaging system with interleaved digitization

Garth Simpson, Ximeng You, Shane Sullivan, and Ryan Muir

Doc ID: 241383 Received 22 May 2015; Accepted 08 Jun 2015; Posted 15 Jun 2015  View: PDF

Abstract: A fast (up to video rate) two-photon excited fluorescence lifetime imaging system based on interleaved digitization is demonstrated. The system is compatible with existing beam-scanning microscopes with minor electronics and software modification. Proof-of-concept demonstrations were performed using laser dyes and biological tissue.

Modeling Bragg coherent x-ray nanobeam diffraction patterns from single crystal films

Stephan Hruszkewycz, Martin Holt, Marc Allain, Virginie Chamard, Sean Polvino, Conal Murray, and Paul Fuoss

Doc ID: 236158 Received 17 Mar 2015; Accepted 04 Jun 2015; Posted 12 Jun 2015  View: PDF

Abstract: X-ray Bragg diffraction experiments that utilize tightly focused coherent beams produce complicated Bragg diffraction patterns that depend on the scattering geometry, the characteristics of the sample, and the properties of the x-ray focusing optic. Here, we use a Fourier-transform-based method of modeling the 2D intensity distribution of a Bragg peak and apply it to the case of thin films illuminated with a Fresnel zone plate in three different Bragg scattering geometries. The calculations agree well with experimental coherent diffraction patterns, demonstrating that nanodiffraction patterns can be modeled at non-symmetric Bragg conditions with this approach -- a capability critical for advancing nanofocused x-ray diffraction microscopy.

Fiber-laser-pumped, high-energy, mid-IR, picosecond optical parametric oscillator with a high-harmonic cavity

Lin Xu, HoYin Chan, Shaif-Ul Alam, David Richardson, and David Shepherd

Doc ID: 237390 Received 02 Apr 2015; Accepted 03 Jun 2015; Posted 04 Jun 2015  View: PDF

Abstract: We demonstrate the generation of high-energy, mid-IR, picosecond pulses in a high-harmonic-cavity optical parametric oscillator (OPO) that has a relatively compact cavity with a length that is a small fraction of that required to match the pump repetition rate. The OPO, based on an MgO-doped periodically poled LiNbO₃ crystal, is pumped by a fiber master-oscillator-power-amplifier system employing direct amplification and delivering 11 μJ, 150 ps pulses at 1035 nm. For a 1.554-m long OPO cavity, resonating near-infrared signal pulses with a repetition rate that is the 193rd harmonic of the 1 MHz pump are demonstrated. The mid-infrared idler output pulses, tunable from 2300nm to 3500nm, are generated at a 1 MHz repetition rate and have energies as high as 1.5 μJ.

Characterization of C-apertures in a successful demonstration of Heat Assisted Magnetic Recording (HAMR)

Sajid Hussain, CHARANJIT BHATIA, Hyunsoo Yang, and Aaron Danner

Doc ID: 240843 Received 14 May 2015; Accepted 28 May 2015; Posted 25 Jun 2015  View: PDF

Abstract: An optical pump-probe setup was used to measure the coercivity change in a heat assisted magnetic recording (HAMR) medium. The incident optical power required to attain the Curie temperature of the medium was determined by calculating its coercivity from BH loops under different illuminating laser powers through use of the Kerr signal in the pump-probe setup. The HAMR medium was then illuminated through an array of square and C-shaped nano-apertures so that the necessary laser power required for magnetic reversal could be compared to the bulk case. Magnetic force microscopy (MFM) and Kerr microscopy revealed that C-apertures were able to heat the magnetic medium and lower the coercivity to achieve magnetic reversal whereas the square apertures were not. The results show that aperture shape and design play a large role in HAMR head designs.

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