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Low-angle optical vortex coronagraphic scatterometer

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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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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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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High-power and low-intensity noise laser at 1064 nm

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OPTICS LETTERS 2016年第17期41卷 4040-4043页

作者： Guiraud, Germain Traynor, Nicholas Santarelli, Giorgio Azur Light Syst Ave Canteranne Pessac France Univ Bordeaux CNRS Inst Opt Lab Photon Numer & Nanosci Talence France

We have developed a single-frequency, narrow-linewidth (Delta nu < 50 kHz) laser operating at 1064 nm with a high output power (50 W). The laser is based on an ytterbium-doped fiber master oscillator power amplifier architecture with an output beam at the diffraction limit. An output power of 50 W is obtained with two amplification stages using a 50 mW diode laser seeder. We have carefully studied the relative intensity noise at each amplification stage. The detrimental effect due to stimulated Brillouin scattering on residual amplitude noise has been observed on the high-power booster stage. After careful optimization, this laser exhibits low intensity noise with a RMS value equal to 0.012% (1 kHz/10 MHz) at 50 W. (C) 2016 Optical Society of America

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

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Subwavelength focusing of terahertz waves in silicon hyperbolic metamaterials

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OPTICS LETTERS 2016年第15期41卷 3539-3542页

作者： Kannegulla, Akash Cheng, Li-Jing Oregon State Univ Sch Elect Engn & Comp Sci Corvallis OR 97331 USA

We theoretically demonstrate the subwavelength focusing of terahertz (THz) waves in a hyperbolic metamaterial (HMM) based on a two-dimensional subwavelength silicon pillar array microstructure. The silicon microstructure with a doping concentration of at least 10(17) cm(-3) offers a hyperbolic dispersion at terahertz frequency range and promises the focusing of terahertz Gaussian beams. The results agree with the simulation based on effective medium theory. The focusing effect can be controlled by the doping concentration, which determines the real part of the out-of-plane permittivity and, therefore, the refraction angles in HMM. The focusing property in the HMM structure allows the propagation of terahertz wave through a subwavelength aperture. The silicon-based HMM structure can be realized using microfabrication technologies and has the potential to advance terahertz imaging with subwavelength resolution. (C) 2016 Optical Society of America

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

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Transition of lasing modes in polymeric opal photonic crystal resonating cavity

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APPLIED OPTICS 2016年第17期55卷 4759-4762页

作者： Shi, Lan-Ting Zheng, Mei-Ling Jin, Feng Dong, Xian-Zi Chen, Wei-Qiang Zhao, Zhen-Sheng Duan, Xuan-Ming Chinese Acad Sci Tech Inst Phys & Chem Lab Organ NanoPhoton 29 Zhongguancun East Rd Beijing 100190 Peoples R China Chinese Acad Sci Tech Inst Phys & Chem Lab Bioinspired Smart Interface Sci 29 Zhongguancun East Rd Beijing 100190 Peoples R China Chinese Acad Sci Chongqing Inst Green & Intelligent Technol 266 Fangzheng AveShuitu Technol Dev Zone Chongqing 400714 Peoples R China

We demonstrate the transition of lasing modes in the resonating cavity constructed by polystyrene opal photonic crystals and 7 wt. % tert-butyl Rhodamine B doped polymer film. Both single mode and multiple mode lasing emission are observed from the resonating cavity. The lasing threshold is determined to be 0.81 mu J/pulse for single mode lasing emission and 2.25 mu J/pulse for multiple mode lasing emission. The single mode lasing emission is attributed to photonic lasing resulting from the photonic bandgap effect of the opal photonic crystals, while the multiple mode lasing emission is assigned to random lasing due to the defects in the photonic crystals. The result would benefit the development of low threshold polymeric solid state photonic crystal lasers. (C) 2016 Optical Society of America

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

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High-resolution low-frequency fluctuation map of a multimode laser diode subject to filtered optical feedback via a fiber Bragg grating

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OPTICS LETTERS 2016年第13期41卷 2950-2953页

作者： Baladi, Fadwa Lee, Min Won Burie, Jean-Rene Bettiati, Mauro A. Boudrioua, Azzedine Fischer, Alexis P. A. Univ Paris 13 Phys Lasers Lab CNRS UMR 7538 Sorbonne Paris Cite F-93430 Villetaneuse France 3SP Technol F-91625 Nozay France

A highly detailed and extended map of low-frequency fluctuations is established for a high-power multi-mode 980 nm laser diode subject to filtered optical feedback from a fiber Bragg grating. The low-frequency fluctuations limits and substructures exhibit substantial differences with previous works. (C) 2016 Optical Society of America

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

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Hyperspectral imaging camera using wavefront division interference

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OPTICS LETTERS 2016年第5期41卷 938-941页

作者： Bahalul, Eran Bronfeld, Assaf Epshtein, Shlomi Saban, Yoram Karsenty, Avi Arieli, Yoel Jerusalem Coll Technol Havaad Haleumi 21 IL-9116001 Jerusalem Israel Ben Gurion Univ Negev IL-8410501 Beer Sheva Israel

An approach for performing hyperspectral imaging is introduced. The hyperspectral imaging is based on Fourier transform spectroscopy, where the interference is performed by wavefront division interference rather than amplitude division interference. A variable phase delay between two parts of the wavefront emanating from each point of an object is created by a spatial light modulator (SLM) to obtain variable interference patterns. The SLM is placed in the exit pupil of an imaging system, thus enabling conversion of a general imaging optical system into an imaging hyperspectral optical system. The physical basis of the new approach is introduced, and an optical apparatus is built. (C) 2016 Optical Society of America

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

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Passively Q-switched erbium-doped fiber laser at C-band region based on WS₂ saturable absorber

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APPLIED OPTICS 2016年第5期55卷 1001-1005页

作者： Ahmad, H. Ruslan, N. E. Ismail, M. A. Reduan, S. A. Lee, C. S. J. Sathiyan, S. Sivabalan, S. Harun, S. W. Univ Malaya Photon Res Ctr Kuala Lumpur 50603 Malaysia VIT Univ Sch Elect Engn Vellore 632014 Tamil Nadu India Univ Malaya Dept Elect Engn Fac Engn Kuala Lumpur 50603 Malaysia

We demonstrate a Q-switched erbium-doped fiber laser using tungsten disulfide (WS2) as a saturable absorber. The WS2 is deposited onto fiber ferrules using a drop-casting method. Passive Q-switched pulses operating in the C-band region with a central wavelength of 1560.7 nm are successfully generated by a tunable pulse repetition rate ranging from 27.2 to 84.8 kHz when pump power is increased from 40 to 220 mW. At the same time, the pulse width decreases from a maximum value of 3.84 mu s to a minimum value of 1.44 mu s. The signal-to-noise ratio gives a stable value of 43.7 dB. The modulation depth and saturation intensity are measured to be 0.99% and 36.2 MW/cm(2), respectively. (C) 2016 Optical Society of America

关键词： Fiber optics Fibers erbium Fibers polarization-maintaining Lasers fiber Lasers distributed-feedback

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Energy-efficient space-time modulation for indoor MISO visible light communications

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OPTICS LETTERS 2016年第2期41卷 329-332页

作者： Zhang, Yan-Yu Yu, Hong-Yi Zhang, Jian-Kang Zhu, Yi-Jun Wang, Tao Natl Digital Switching Syst Engn & Technol Res Ct Zhengzhou 450000 Henan Province Peoples R China McMaster Univ Dept Elect & Comp Engn 1280 Main St W Hamilton ON L8S 4K1 Canada

We consider an indoor multi-input single-output (MISO) visible light communication (VLC) system without channel state information at the transmitter. For such a system, an energy-efficient time-collaborative modulation (TCM) constellation is first designed by minimizing a total optical power subject to a fixed minimum Euclidean distance. Then, a new space-time transmission scheme is proposed. Comprehensive computer simulations indicate that our proposed design always has better average error performance within illumination coverage area than the currently available schemes for this application.

关键词： Fiber optics and optical communications Lasers distributed-feedback

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