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Optics Letters

Tarek Labidi, Ihsan Fsaifes, Weilin Xie, Debanuj Chatterjee, Fabienne Goldfarb, Fabien Bretenaker
We experimentally investigate the evolution of the direct detection noise figure of a nondegenerate phase-sensitive amplifier based on a nonlinear fiber, as a function of the relative phase between the signal, idler, and pump, all other parameters remaining fixed. The use of a fiber with a high stimulated Brillouin scattering threshold permits us to investigate the full range of phase-sensitive gain and noise figure without pump dithering. Good agreement is found with theory, both for signal only and combined signal and idler direct detections...
September 15, 2018: Optics Letters
Yigit Ozan Aydin, Vincent Fortin, Réal Vallée, Martin Bernier
We report the demonstration of a 2824 nm passively cooled erbium-doped fluoride fiber laser delivering a record average output power of 41.6 W in continuous-wave operation. The splice-less cavity is based on intra-core fiber Bragg gratings written directly in the active erbium-doped fluoride fiber, which is bidirectionally pumped at 980 nm to reduce heat load. To the best of our knowledge, this result is the highest average output power achieved with a mid-infrared fiber laser. The long-term performance of different protective endcaps is also investigated at high-power operation...
September 15, 2018: Optics Letters
Nuo Xu, Meiping Zhu, Yingjie Chai, Behshad Roshanzadeh, S T P Boyd, Wolfgang Rudolph, Yuanan Zhao, Rong Chen, Jianda Shao
HfO2 /SiO2 bilayer coatings and multilayer high-reflection coatings without and with a modified co-evaporated interface (MCEI) have been prepared. An MCEI is designed to be evaporated at an oxygen-deficient environment to achieve higher absorption than the conventional discrete interface. Capacitance-voltage measurements and absorption measurements demonstrate that an MCEI increases the trap density and leads to higher absorption. The laser-induced damage threshold and nano-indenter test results indicate that the MCEI multilayer coating exhibits better laser resistance and mechanical property, despite the larger absorption...
September 15, 2018: Optics Letters
Junchao Zhang, Jianbo Shao, Haibo Luo, Xiangyue Zhang, Bin Hui, Zheng Chang, Rongguang Liang
We propose a polarization demosaicing convolutional neural network to address the image demosaicing issue, the last unsolved issue in microgrid polarimeters. This network learns an end-to-end mapping between the mosaic images and full-resolution ones. Skip connections and customized loss function are used to boost the performance. Experimental results show that our proposed network outperforms other state-of-the-art methods by a large margin in terms of quantitative measures and visual quality.
September 15, 2018: Optics Letters
Jiaxiong Li, Lulu Wang, Jiangbing Du, Shoulin Jiang, Lin Ma, Chengkun Cai, Long Zhu, Andong Wang, Ming-Jun Li, Hao Chen, Jian Wang, Zuyuan He
We design and experimentally demonstrate a few-mode Raman amplifier over the C+L band with a flat on-off gain of ∼4  dB, for the first time, to the best of our knowledge. A state-of-the-art gain bandwidth of 75 nm (1530-1605 nm) is achieved. The wavelength-dependent gain for both LP01 and LP11 modes is about 0.6 dB, and the maximum mode-dependent gain is less than 0.3 dB. Mode-division multiplexed optical transmissions are performed over 75 km few-mode fiber assisted by the proposed Raman amplifier...
September 15, 2018: Optics Letters
Pavel Yu Shapochkin, Maksim S Lozhkin, Ivan A Solovev, Olga A Lozhkina, Yury P Efimov, Sergey A Eliseev, Vyacheslav A Lovcjus, Gleb G Kozlov, Anastasia A Pervishko, Dmitry N Krizhanovskii, Paul M Walker, Ivan A Shelykh, Maurice S Skolnick, Yury V Kapitonov
We study the influence of optical selection rules and polarization splittings on properties of exciton polaritons in a planar AlGaAs waveguide containing embedded GaAs quantum wells. We demonstrate that transverse electric and transverse magnetic modes couple differently with light- and heavy-hole quantum well excitons, which leads to distinct polarization splittings of the resulting polariton modes. The experimental data are in good agreement with modeling based on theoretical data for the optical selection rules for quantum well excitons...
September 15, 2018: Optics Letters
Jonas Westberg, Lukasz A Sterczewski, Filippos Kapsalidis, Yves Bidaux, Johanna M Wolf, Mattias Beck, Jérôme Faist, Gerard Wysocki
In this Letter, we report on sub-millisecond response time mid-infrared dual-comb spectroscopy using a balanced asymmetric (dispersive) dual-comb setup with a matched pair of plasmon-enhanced-waveguide dispersion-compensated quantum cascade lasers. The system performance is demonstrated by measuring spectra of Bromomethane (CH3 Br) and Freon 134a (CH2 FCF3 ) at approximately 7.8 μm. A purely computational phase and timing-correction procedure is used to validate the coherence of the quantum cascade lasers frequency combs and to enable coherent averaging over the time scales investigated...
September 15, 2018: Optics Letters
Yong Zhang, Yu He, Qingming Zhu, Xuhan Guo, Ciyuan Qiu, Yikai Su, Richard Soref
Energy-efficient tunability is highly desired for silicon photonic devices. We demonstrate a thermo-optic tunable filter with an ultra-high tuning efficiency based on a suspended photonic crystal nanobeam cavity. Attributed to the ultra-small mode volume and free-standing waveguide structure, a tuning efficiency of 21 nm/mW is achieved over a wide single-resonance tuning range of ∼43.9  nm. The 10%-90% switching times are 67.0 μs and 68.8 μs for the rising edge and the falling edge, respectively. The demonstrated energy-efficient tunable device can find applications in reconfigurable photonic integrated circuits...
September 15, 2018: Optics Letters
Qianghua Chen, Binchao Liu, Yongxi He, Huifu Luo, Weiwei Lv
Wave plates (WPs) are key components in optical polarization systems whose phase retardations should be measured accurately. The key point of most light extinction methods focuses on how to precisely judge the system's extinction state and then confirm corresponding angle positions of the optical components. Usually the extinction state of a measurement system is judged by detecting residue of outgoing light intensity. In this Letter, a method of measuring the phase retardation of an arbitrary WP based on magneto-optical modulation is proposed...
September 15, 2018: Optics Letters
Arohi Jain, Thomas Gaumnitz, Alexander Bray, Anatoli Kheifets, Hans Jakob Wörner
Attosecond photoemission delays for all the valence (5p3/2 , 5p1/2 , 5s, 4d5/2 , 4d3/2 ) subshells of xenon have been accessed using the interferometric RABBITT technique. The 4d subshell delays in Xe have been accessed for the first time, to the best of our knowledge, due to the high photon energy used. A novel technique of single-shot referencing in the collinear back-focusing geometry has been introduced. This enables us to distinguish the signal from principal photoelectron peaks due to ionization by extreme ultraviolet radiation only and infrared-induced sideband contributions, especially in the regions of spectral overlap...
September 15, 2018: Optics Letters
Thomas Gaumnitz, Arohi Jain, Hans Jakob Wörner
An annular infrared (IR) laser beam has been used for high-order harmonic generation reaching a cut-off energy of 90 eV for extreme-ultraviolet-infrared (XUV-IR) pump-probe experiments in an intrinsically stable attosecond beamline. The generation of harmonics along the laser axis in the missing portion of the laser beam decreases the IR power load on thin metallic foils that are used for removing the residual IR and shaping the XUV pulses from high-harmonic generation. This finds applications in high-average-power few-cycle laser systems, where high-average IR power destroys the foils...
September 15, 2018: Optics Letters
Mengge Wu, Zijun Wang, Xiaolin Wang, Junsheng Yu
A heterojunction consisting of poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-(4,4'-(N-(4-butylphenyl)))] (TFB) and aluminum tris(8-hydroxyquinolinate) (Alq3 ) is applied for fabricating an organic light-emitting photodetector (OLEP), where TFB and Alq3 behave as an ultraviolet response center and a green light emitter, respectively. The OLEP shows a detectivity of 1.4×1011 Jones and a luminance of 11,569  cd/m2 . Thermal active delay fluorescent material is introduced in the TFB matrix to improve photodetection property...
September 15, 2018: Optics Letters
Artem Boriskin, Valter Drazic, Ray Keating, Mitra Damghanian, Oksana Shramkova, Laurent Blondé
This publisher's note corrects an error in the reference section of Opt. Lett.43, 4053 (2018)OPLEDP0146-959210.1364/OL.43.004053.
September 15, 2018: Optics Letters
Jeremy Vatin, Damien Rontani, Marc Sciamanna
We analyze the performance of a reservoir computer based on time-delay feedback and optical injection, which is drawing benefits from the high-speed polarization dynamics of a vertical cavity surface emitting laser. We show that such a system has high computation performance and yields deeper memory than an existing single-mode laser-based reservoir computer. Performance is demonstrated on several benchmarking tasks. In particular, the error rate is an order of magnitude smaller when performing channel equalization...
September 15, 2018: Optics Letters
Siddharth Sivankutty, Viktor Tsvirkun, Géraud Bouwmans, Esben Ravn Andresen, Dan Oron, Hervé Rigneault, Miguel A Alonso
A simple technique for far-field single-shot noninterferometric determination of the phase transmission matrix of a multicore fiber with over 100 cores is presented. This phase retrieval technique relies on the aperiodic arrangement of the cores.
September 15, 2018: Optics Letters
Pierre Pichon, Frédéric Druon, Jean-Philippe Blanchot, François Balembois, Patrick Georges
We report, to the best of our knowledge, the first light-emitting diode (LED)-pumped Cr:LiSAF laser, in both quasi-continuous-wave (QCW) and passively Q-switched operation. This Letter is based on the recent development of LED-pumped luminescent concentrators (LCs). Combining the capacity of high-density integration of blue LEDs with the excellent properties of Ce:YAG LCs, this new pump source can deliver high irradiance (7.3  kW/cm2 ) in the visible to pump Cr:LiSAF. The Cr:LiSAF laser demonstrates an energy of 8...
September 15, 2018: Optics Letters
Takashi Tanaka
We propose a simple scheme for difference frequency generation in free electron lasers (FELs), in which the electron beam interacts with a dual-frequency laser and emits intense coherent radiation at the difference frequency. We analytically show that the microbunch formation in the electron beam, which is the most important process in FELs, is dominated by nonlinear wave mixing in the proposed scheme. Numerical examples of applying the proposed scheme to generating terahertz radiation are presented as one of the most important applications...
September 15, 2018: Optics Letters
Benjamin Craig, Vivek Raj Shrestha, Jiajun Meng, Jasper J Cadusch, Kenneth B Crozier
We computationally reconstruct short- to long-wave infrared spectra using an array of plasmonic metasurface filters. We illuminate the filter array with an unknown spectrum and measure the optical power transmitted through each filter with an infrared microscope to emulate a filter-detector array system. We then use the recursive least squares method to determine the unknown spectrum. We demonstrate our method with light from a blackbody. We also demonstrate it with spectra generated by passing the light from the blackbody through various materials...
September 15, 2018: Optics Letters
Leo A Bahr, Peter Fendt, Yin Pang, Jürgen Karl, Thomas Hammer, Andreas S Braeuer, Stefan Will
We present a novel non-invasive laser-based tool for tracer-free spatially resolved temperature measurement in superheated water vapor at atmospheric pressure. The technique exploits the temperature sensitivity of the rotational-vibrational Raman spectrum of the v1 stretching vibration. This Letter demonstrates the Raman sensor, its application to a steam gasification reactor, and four methods to analyze the Raman spectra in order to obtain the temperature: an equal intensity point approach, a pseudo-isosbestic point approach, and two approaches based on the reconstruction of the Raman band by Gaussian/Lorentzian profiles...
September 15, 2018: Optics Letters
Meng Wang, Takashi Hosoda, Jiang Jiang, Leon Shterengas, Gela Kipshidze, Aaron Stein, Tao Feng, Gregory Belenky
A three-stage cascade GaSb-based diode laser heterostructure with an enhanced optical gain spectral bandwidth was designed and fabricated. The gain broadening was achieved by varying the thickness of the type-I quantum wells in different stages of the cascade active region from 10 to 14 nm. The structures were processed into bent ridge gain chips with virtually eliminated feedback from the anti-reflection-coated angled facet. The external cavity devices based on a novel gain chip design demonstrated a record wide tuning range from 2...
September 15, 2018: Optics Letters
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