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Lasing in imperfectly aligned cholesterics

APPLIED OPTICS 2015年第33期54卷 9644-9653页

作者： Dudok, T. H. Savaryn, V. I. Krupych, O. M. Fechan, A. V. Lychkovskyy, E. Cherpak, V. V. Pansu, B. Nastishin, Yu. A. Vlokh Inst Phys Opt UA-79005 Lvov Ukraine Lviv Polytech Natl Univ UA-79013 Lvov Ukraine Lviv Danylo Halytsky Natl Med Univ UA-79010 Lvov Ukraine Univ Paris 11 Lab Phys Solides UMR 8502 F-91405 Orsay France

Optically pumped light emissions in imperfectly aligned dye-doped cholesteric cells with glance and frosted glass substrates of three different cell gap thicknesses are experimentally studied. Alignment imperfections show up in emission spectra by a broadening of the photonic bandgap (PhBG) lasing (allowed) lines at short- and long-wavelength PhBG edges and by an additional (forbidden) emission line inside the PhBG. Forbidden and allowed lines differ distinctively by their stability in the course of pumping. The origin of the forbidden line is discussed. (C) 2015 Optical Society of America

关键词： Dye lasers Lasers distributed-feedback Scattering stimulated

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Slowing down light to 300 km/s in a deuterium-loaded fiber Bragg grating

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OPTICS LETTERS 2015年第7期40卷 1524-1527页

作者： Skolianos, George Arora, Arushi Bernier, Martin Digonnet, Michel J. F. Stanford Univ Edward L Ginzton Lab Stanford CA 94305 USA Univ Laval COPL Quebec City PQ G1V 0A6 Canada

We report light propagation with a group velocity of only 300 km/s, a group index of 1010, and a group delay of 42 ns, in a strong apodized fiber Bragg grating 12.5 mm in length. The grating was fabricated in a deuterium-loaded fiber using a femtosecond laser and a phase mask, followed by annealing to reduce residual losses. Data analysis indicates a strong index modulation of 1.98 x 10(-3) and an ultra-low single-pass power loss of 0.010 dB. (C) 2015 Optical Society of America

关键词： Fiber optics sensors Fibers polarization-maintaining Fiber Bragg gratings Lasers distributed-feedback

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Flexible wavelength de-multiplexer for elastic optical networking

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OPTICS LETTERS 2016年第10期41卷 2241-2244页

作者： Zhou, Rui Pascual, M. Deseada Gutierrez Anandarajah, Prince M. Shao, Tong Smyth, Frank Barry, Liam P. Dublin City Univ Sch Elect Engn Radio & Opt Commun Lab Dublin 9 Ireland Dublin City Univ Invent Ctr Pilot Photon Ltd Dublin 9 Ireland

We report an injection locked flexible wavelength de-multiplexer (de-mux) that shows 24-h frequency stability of 1 kHz for optical comb-based elastic optical networking applications. We demonstrate 50 GHz, 87.5 GHz equal spacing and 6.25G-25G-50 GHz, 75G-50G-100 GHz unequal spacing for the de-multiplexer outputs. We also implement an unequally spaced (75G-50G-100 GHz), mixed symbol rate (12.5 GBaud and 40 GBaud) and modulation format (polarization division multiplexed quadrature phase shift keying and on-off keying) wavelength division multiplexed transmission system using the de-multiplexer outputs. The results show 0.6 dB receiver sensitivity penalty, at 7% hard decision forward error correction coding limit, of the 100 km transmitted de-mux outputs when compared to comb source seeding laser back-to-back. (C) 2016 Optical Society of America

关键词： Coherent communications Buffers couplers routers switches and multiplexers Lasers distributed-feedback Lasers injection-locked

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Multiwavelength shearing interferometry for measuring the slopes, curvatures, and shapes of thin films/substrate systems

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OPTICS LETTERS 2013年第24期38卷 5446-5449页

作者： Zhang, Changxing Dong, Xuelin Feng, Xue Hwang, Keh-Chih Tsinghua Univ Dept Elect Engn AML Beijing 100084 Peoples R China Tsinghua Univ Ctr Mech & Mat Beijing 100084 Peoples R China China Univ Petr Key Lab Petr Engn Beijing 102249 Peoples R China

Multiwavelength shearing interferometry, a full-field, real-time, and vibration-insensitive method with enhanced accuracy, is proposed. Theoretically, the more wavelengths that are used for shearing interferometers, the higher the precision that can be achieved in the measurement of slopes, curvatures, and the shapes of reflective surfaces. A spherical mirror with specified curvature radius is used to calibrate this method, and then the nonuniform deformation and shape of the TiNi film/Si substrate system are obtained experimentally. (C) 2013 Optical Society of America

关键词： Surface measurements figure Lasers distributed-feedback Diffraction gratings

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Low-angle optical vortex coronagraphic scatterometer

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OPTICS LETTERS 2016年第21期41卷 4915-4918页

作者： Wan, Lingyu Ruane, Garreth J. Swartzlander, Grover A., Jr. Rochester Inst Technol Chester F Carlson Ctr Imaging Sci 54 Lomb Mem Dr Rochester NY 14623 USA Guangxi Univ Coll Phys Sci & Technol Guangxi Key Lab Relativist Astrophys Nanning 530004 Peoples R China

The important, but difficult-to-measure zero and low-angle scattering spectrum, as well as the broader angular spectrum, was obtained by use of an optical vortex corona-graphic scatterometer (patent pending). The experimental measurements agreed well with the predictions from the Mie scattering theory. High contrast discrimination allowed us to remove the unscattered coherent illumination, revealing a low-angle superimposed scattered signal. (C) 2016 Optical Society of America

关键词： Optical vortices Digital image processing Scattering measurements Lasers distributed-feedback Scattering particles

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Thermally induced light-scattering effects as responsible for the degradation of cholesteric liquid crystal lasers

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OPTICS LETTERS 2015年第7期40卷 1262-1265页

作者： Etxebarria, J. Ortega, J. Folcia, C. L. Sanz-Enguita, G. Aramburu, I. Univ Basque Country Fac Sci & Technol Dept Condensed Matter Phys Bilbao 48080 Spain Univ Basque Country Fac Sci & Technol Dept Appl Phys 2 Bilbao 48080 Spain Univ Basque Country Fac Engn ETSI Dept Appl Phys 1 Bilbao 48013 Spain

We have studied the degradation process of the laser emission in a cholesteric liquid crystal laser. We have found that there exists a negative correlation between the laser efficiency and the amount of light scattered by the liquid-crystal sample in the illuminated area. The growth of scattering is attributed to the appearance of small imperfections generated in the sample as a result of certain thermal processes that involve the dye molecules. The scattering implies an increase of the coefficient of distributed losses, which is the main response of the rise of the laser threshold. (C) 2015 Optical Society of America

关键词： Lasers distributed-feedback Liquid crystals Liquid-crystal devices Scattering Rayleigh

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Short cavity-length random fiber laser with record power and ultrahigh efficiency

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OPTICS LETTERS 2016年第3期41卷 571-574页

作者： Du, Xueyuan Zhang, Hanwei Wang, Xiaolin Zhou, Pu Liu, Zejin Natl Univ Def Technol Coll Optoelect Sci & Engn Changsha 410073 Hunan Peoples R China

We report the result of achieving a random fiber laser (RFL) with record 200-W-level power output. The highest output power is realized by a simple 120 m long cavity at a working wavelength of 1173 nm while pumping at 1120 nm. The maximum observed optical-to-optical efficiency reaches similar to 89%, which is believed to be the highest value ever reported for RFLs. In addition, numerical calculations on different order Raman Stokes wave thresholds based on the theoretical model are carried out for comparison with the experimental data. The presented work effectively advances the power scalability, and the numerical model well describes the lasing thresholds in such short cavity RFLs. (C) 2016 Optical Society of America

关键词： Lasers distributed-feedback Scattering Rayleigh Scattering stimulated Raman

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SUB-MHZ SPECTRAL LINEWIDTH IN 1.5-MU-M SEPARATE-CONFINEMENT-HETEROSTRUCTURE (SCH) QUANTUM-WELL DFB LDS

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ELECTRONICS LETTERS 1989年第5期25卷 356-357页

作者： TAKANO, S SASAKI, T YAMADA, H KITAMURA, M MITO, I Optoelectron. Res. Labs. NEC Corp. Kawasaki Japan

Extremely narrow spectral-linewidth characteristics in 1.5 mu m GaInAs/GaInAsP separate-confinement-heterostructure (SCH), quantum-well (QW), distributed-feedback, laser diodes (DFB LDs) are reported. Narrower linewidths were obtained in lasers with smaller numbers of quantum wells. Sub-MHz linewidth was achieved for the first time in single laser diodes.

关键词： 1 MHz 1.5 micron GaInAs-GaInAsP III-V semiconductors SCH-QW-DFB-LD distributed feedback lasers distributed-feedback gallium arsenide indium compounds laser diodes narrow spectral-linewidth characteristics optical communication equipment quantum-well DFB LDs semiconductor junction lasers semiconductors separate-confinement-heterostructure single laser diodes

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Random Brillouin fiber laser for tunable ultra-narrow linewidth microwave generation

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OPTICS LETTERS 2016年第20期41卷 4839-4842页

作者： Xiang, Dao Lu, Ping Xu, Yanping Chen, Liang Bao, Xiaoyi Univ Ottawa Dept Phys Ottawa ON K1N 6N5 Canada

Studies about random lasing phenomena taking place in disordered structures with amplification are gaining great interest, as they can support dual wavelength lasing without cavity length restriction and, hence, the tunable beat frequency in a microwave can be created in a random cavity and be amplified for applications in the information and communication technology. Here, we present a novel random Brillouin fiber laser scheme using the stimulated Brillouin scattering as gain and strong Rayleigh scattering feedback (10 km) in the single-mode fiber. The high degree of mutual coherence between the two Stokes beams from two different lasers leads to the generation of tunable ultra-narrow linewidth microwave signals (<10 Hz at 3 dB bandwidth) with a 70 dB contrast. This offers a simple and cost-effective design for microwave sources. (C) 2016 Optical Society of America.

关键词： Radio frequency photonics Lasers distributed-feedback Scattering Rayleigh Scattering stimulated Brillouin

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Coherence measurement with digital micromirror device

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OPTICS LETTERS 2014年第4期39卷 1034-1037页

作者： Partanen, Henri Turunen, Jari Tervo, Jani Univ Eastern Finland Inst Photon FI-80101 Joensuu Finland

We measure the complex-valued spatial coherence function of a multimode broad-area laser diode using Young's classical double slit experiment realized with a digital micromirror device. We use this data to construct the coherent modes of the beam and to simulate its propagation before and after the measurement plane. When comparing the results to directly measured intensity profiles, we find excellent correspondence to the extent that even small details of the beam can be predicted. We also consider the number of measurement points required to model the beam with sufficient accuracy. (C) 2014 Optical Society of America

关键词： Coherence Modes Fringe analysis Lasers distributed-feedback

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