2010

• Record 25 of
  
  Title:High-precision digital synchronous system in the physical diagnosis of multi-beam laser target system
  
  Author(s):Xue, Yingdong(1,2); Bai, Yonglin(3); Liu, Baiyu(3); Wang, Bo(3); Li, Yan(1,2); Ouyang, Xian(3); Gou, Yongsheng(1,2); Zhang, Wei(1,2)
  Source: Proceedings of SPIE - The International Society for Optical Engineering  Volume: 7656  Issue: PART 1  DOI: 10.1117/12.864668  Published: 2010  
  Abstract:A high-precision synchronous system has been developed to control the diagnostic equipments in the multi-beam laser target experiment. In the system, both digital delay and analog delay techniques are used simultaneously to realize the high-precision time delay. By adopting the embedded intelligent chip FPGA, the resource consumption of the system is obviously reduced; the performance of the digital delay part is improved. In the analog delay part, the capacitor charging and discharging techniques are used to realize the delay resolution of 5 ps. To reduce the impact of the random trigger signals, the jitter compensation circuit is also used in the design. The high-precision time delay and strong antiinterference ability of the system are proved by the experimental results. © 2010 Copyright SPIE - The International Society for Optical Engineering.
  Accession Number: 20105013487623
• Record 26 of
  
  Title:Design and optimization of low-dispersion high-nonlinear photonic crystal fiber for four-wave mixing
  
  Author(s):Zhang, Yani(1,2)
  Source: Guangxue Xuebao/Acta Optica Sinica  Volume: 30  Issue: SUPPL.  DOI: 10.3788/AOS201030.s100203  Published: December 2010  
  Abstract:A novel type of photonic crystal fiber (PCF) with low dispersion and high nonlinearity for four-wave mixing is proposed. This kind of fiber is composed of a solid silica core and a cladding with squeezed-hexagonal-lattice elliptical air-hole along the fiber length. Its dispersion and nonlinearity coefficient are investigated simultaneously by using full vectorial finite element method. Numerical results show that proposed highly-nonlinear low-dispersion fiber has the total dispersion as low as ±2.5 ps/(nm·km) over ultra-broad wavelength range from 1.43 μm to 1.8 μm by adjusting the structure parameters of photonic crystal fiber, such as the hexagonal squeezing ratio, the relative air hole size and the air hole ellipticity, and the corresponding nonlinearity coefficient is about 150 (W·km)-1 at 1.55 μm. The proposed PCF with low ultra-flattened dispersion, high nonlinearity and high birefringence can have important applications on the four-wave mixing.
  Accession Number: 20111813958808
• Record 27 of
  
  Title:Experimental study on phase-locking of two high-power all-fiber lasers
  
  Author(s):Zhao, Baoyin(1,2); Duan, Kailang(1); Liu, Yang(3); Zhao, Wei(1)
  Source: Optics Communications  Volume: 283  Issue: 11  DOI: 10.1016/j.optcom.2010.02.004  Published: June 1, 2010  
  Abstract:By using a novel mutual injection technique, phase-locking and coherent combining of two high-power all-fiber lasers are realized and experimentally demonstrated. Steady interference strips with high visibility of 46% are observed. The coherent combined 407 W CW output power with a power-combining efficiency of up to 98% is obtained. The laser array works well with excellent stability. In the long time of high-power operation no thermal distortions or damages are observed. The proposed technique can be used to further scale up the coherent combined output power of high-power fiber lasers. © 2010 Elsevier B.V. All rights reserved.
  Accession Number: 20101412822804
• Record 28 of
  
  Title:Spatial and temporal evolution of transient stimulated-Brillouin-scattering slow-light pulse in an optical fiber
  
  Author(s):Ren, Liyong(1); Yang, Yanlong(1); Zhao, Wei(1); Tomita, Yasuo(2)
  Source: Proceedings of SPIE - The International Society for Optical Engineering  Volume: 7612  Issue:   DOI: 10.1117/12.840631  Published: 2010  
  Abstract:Slow-light technology via stimulated Brillouin scattering (SBS) in an optical fiber has attracted a lot of attention owing to its flexible gain spectrum tailoring capacity, good compatibility with existing telecommunication systems, and great application for photonic switchers and routers in ultra-high-speed photonic networks. In this paper we present a general theoretical model for analyzing the dynamic behavior of the nonlinear interactions of the transient SBS process based on the three-wave coupled-amplitude equations for the pump, Stokes and acoustic waves. Spatial and temporal evolution of a generating slow-light pulse with the duration of sub-nanosecond under double broadband pump case is accurately simulated owing to the fact that our model includes the second-order derivative of the acoustic field. We conclude that the origin of the pulse broadening and distortion can be explained in terms of the temporal decay of the induced acoustic field. © 2010 Copyright SPIE - The International Society for Optical Engineering.
  Accession Number: 20101812909864
• Record 29 of
  
  Title:Efficient green-light generation by frequency doubling of a picosecond all-fiber ytterbium-doped fiber amplifier in PPKTP waveguide inscribed by femtosecond laser direct writing
  
  Author(s):Tu, Chenghou(1); Huang, Zhangchao(1); Lou, Kai(1); Liu, Hongjun(2); Wang, Yishan(2); Li, Yongnan(1); Lu, Fuyun(1); Wang, Hui-Tian(1,3)
  Source: Optics Express  Volume: 18  Issue: 24  DOI: 10.1364/OE.18.025183  Published: November 22, 2010  
  Abstract:We have demonstrated an ultrashort, compact green light radiation by frequency doubling of an all-fiber ytterbium-doped fiber laser source in a PPKTP waveguide fabricated by femtosecond laser pulses. Using the fabricated PPKTP waveguide crystal containing a 10 mm single grating with a period of 9.0 μm, we generate 310 mW of picosecond radiation at 532 nm for a fundamental power of 1.6W, corresponding to a conversion efficiency of 19.3%. The temperature tuning range of 8°C is achieved for a fixed fundamental wavelength of 1064 nm, the FWHM of the wavelength tuning curve is 4.2 nm at room temperature. The generated ultrashort pulses at 532 nm are of great importance and have comprehensive applications in photobiology research and high-resolution spectroscopy. © 2010 Optical Society of America.
  Accession Number: 20104913463928
• Record 30 of
  
  Title:Fluoride sensitive optical probe of microstructured polymer optical fiber modified with sol-gel thin film
  
  Author(s):Yang, Xing-Hua(1,3); Peng, Li-Rong(1); Teng, Ping-Ping(2); Yuan, Li-Bo(1); Wang, Li-Li(3)
  Source: Guangxue Jingmi Gongcheng/Optics and Precision Engineering  Volume: 18  Issue: 1  DOI:   Published: January 2010  
  Abstract:An optical fluoride probe was fabricated based on Microstructured Polymer Optical Fibers (MPOFs) modified by morin-Al complex doped silica gel films. The structure of this probe was based on microstructured polymer optical fibers with microholes and these microholes could be used as the substrate of sensing materials and minor reaction pools. The deposition of sensing layer was realized by a sol-gel process. When the sol doped with morin-Al was inhaled into the optical fiber, the sensing layer was formed on the inner wall. Furthermore, the trace liquid could be hold in the MPOF, and the process of sensing were carried out in the microholes of MPOF. The sensing process was undertaken based on fluorescence process, and the sensing probe shows different fluorescence intensities to different fluoride ion concentrations in the aqueous solution, for the fluoride ion has a stronger quenching effect to the morin-Al in gel matrix. Experimental results show that the range of response is 5-50 mmol/L under the condition of pH in 4.6.
  Accession Number: 20101212786739
• Record 31 of
  
  Title:Ultrashort optical pulse monitoring using asynchronous optical sampling technique in highly nonlinear fiber
  
  Author(s):Tang, Dingkang(1,2); Zhang, Jianguo(1,3); Liu, Yuanshan(1); Zhao, Wei(1)
  Source: Chinese Optics Letters  Volume: 8  Issue: 7  DOI: 10.3788/COL20100807.0630  Published: July 2010  
  Abstract:An asynchronous optical sampling scheme based on four-wave mixing (FWM) in highly nonlinear fiber (HNLF) is experimentally demonstrated. Based on this scheme, 10-GHz input pulse train with 1.8-ps pulse width is successfully sampled in 100-m HNLF. A single pulse at 10 GHz with 2.3-ps pulse width is rebuilt by using a 50-MHz frequency tunable free-running fiber laser as the sampling pulse source (SPS). 40-GHz pulse train is used as the input signal. The rebuilt waveforms, together with the low-jitter eye diagram, are also presented. © 2010 Chinese Optics Letters.
  Accession Number: 20103113111580
• Record 32 of
  
  Title:Incremental pairwise discriminant analysis based visual tracking
  
  Author(s):Wen, Jing(1); Gao, Xinbo(1); Li, Xuelong(2); Tao, Dacheng(3); Li, Jie(1)
  Source: Neurocomputing  Volume: 74  Issue: 1-3  DOI: 10.1016/j.neucom.2010.07.014  Published: December 2010  
  Abstract:The distinguishment between the object appearance and the background is the useful cues available for visual tracking, in which the discriminant analysis is widely applied. However, due to the diversity of the background observation, there are not adequate negative samples from the background, which usually lead the discriminant method to tracking failure. Thus, a natural solution is to construct an object-background pair, constrained by the spatial structure, which could not only reduce the neg-sample number, but also make full use of the background information surrounding the object. However, this idea is threatened by the variant of both the object appearance and the spatial-constrained background observation, especially when the background shifts as the moving of the object. Thus, an incremental pairwise discriminant subspace is constructed in this paper to delineate the variant of the distinguishment. In order to maintain the correct the ability of correctly describing the subspace, we enforce two novel constraints for the optimal adaptation: (1) pairwise data discriminant constraint and (2) subspace smoothness. The experimental results demonstrate that the proposed approach can alleviate adaptation drift and achieve better visual tracking results for a large variety of nonstationary scenes. © 2010 Elsevier B.V.
  Accession Number: 20104813445440
• Record 33 of
  
  Title:Electron spin dynamics in heavily Mn-doped (Ga,Mn)As
  
  Author(s):Zhu, Yonggang(1,2); Han, Lifen(1); Chen, Lin(1); Zhang, Xinhui(1); Zhao, Jianhua(1)
  Source: Applied Physics Letters  Volume: 97  Issue: 26  DOI: 10.1063/1.3531754  Published: December 27, 2010  
  Abstract:Electron spin relaxation and related mechanisms in heavily Mn-doped (Ga,Mn)As are studied by performing time-resolved magneto-optical Kerr effect measurements. At low temperature, s-d exchange scattering dominates electron spin relaxation, whereas the Bir-Aronov-Pikus mechanism and Mn impurity scattering play important roles at high temperature. The temperature-dependent spin relaxation time exhibits an anomaly around the Curie temperature (T c) that implies that thermal fluctuation is suppressed by short-range correlated spin fluctuation above Tc. © 2010 American Institute of Physics.
  Accession Number: 20110213562261
• Record 34 of
  
  Title:SOA-based actively mode-locked fiber ring laser by forward injecting an external pulse train
  
  Author(s):Yan, Shuangyi(1); Zhang, Jian-Guo(2); Zhao, Wei(1)
  Source: Optics Communications  Volume: 283  Issue: 1  DOI: 10.1016/j.optcom.2009.09.032  Published: January 1, 2010  
  Abstract:An actively mode-locked fiber ring laser based on cross-gain modulation (XGM) in a semiconductor optical amplifier (SOA) is demonstrated to operate stably with a simple configuration. By forward injecting an easily-generated external pulse train, the mode-locked fiber laser can generate an optical-pulse sequence with pulsewidth about 6 ps and average output power about 7.9 mW. The output pulses show an ultra-low RMS jitter about 70.7 fs measured by a RF spectrum analyzer. The use of the proposed forward-injection configuration can realize the repetition-rate tunability from 1 to 15 GHz for the generated optical-pulse sequences. By employing a wavelength-tunable optical band-pass filter in the laser cavity, the operation wavelength of the designed SOA-based actively mode-locked fiber laser can be tuned continuously in a wide span between 1528 and 1565 nm. The parameters of external-injection optical pulses are studied experimentally to optimize the mode-locked fiber laser. © 2009 Elsevier B.V.
  Accession Number: 20095112559604
• Record 35 of
  
  Title:A multi-frame image super-resolution method
  
  Author(s):Li, Xuelong(1); Hu, Yanting(2); Gao, Xinbo(3); Tao, Dacheng(4); Ning, Beijia(3)
  Source: Signal Processing  Volume: 90  Issue: 2  DOI: 10.1016/j.sigpro.2009.05.028  Published: February 2010  
  Abstract:Multi-frame image super-resolution (SR) aims to utilize information from a set of low-resolution (LR) images to compose a high-resolution (HR) one. As it is desirable or essential in many real applications, recent years have witnessed the growing interest in the problem of multi-frame SR reconstruction. This set of algorithms commonly utilizes a linear observation model to construct the relationship between the recorded LR images to the unknown reconstructed HR image estimates. Recently, regularization-based schemes have been demonstrated to be effective because SR reconstruction is actually an ill-posed problem. Working within this promising framework, this paper first proposes two new regularization items, termed as locally adaptive bilateral total variation and consistency of gradients, to keep edges and flat regions, which are implicitly described in LR images, sharp and smooth, respectively. Thereafter, the combination of the proposed regularization items is superior to existing regularization items because it considers both edges and flat regions while existing ones consider only edges. Thorough experimental results show the effectiveness of the new algorithm for SR reconstruction. © 2009 Elsevier B.V. All rights reserved.
  Accession Number: 20093912346575
• Record 36 of
  
  Title:Generation of multiple spherical spots with a radially polarized beam in a 4π focusing system
  
  Author(s):Yan, Shaohui(1); Yao, Baoli(1); Zhao, Wei(1); Lei, Ming(2)
  Source: Journal of the Optical Society of America A: Optics and Image Science, and Vision  Volume: 27  Issue: 9  DOI: 10.1364/JOSAA.27.002033  Published: September 1, 2010  
  Abstract:We demonstrate the possibility of creating multiple spherical spots in a 4-π- focusing system with a radially polarized beam. Using spherical waves to expand the plane wave factor in the Richards-Wolf integral, it is found that a proper spatial modulation in the amplitude of the input field with radial polarization can form multiple spherical spots with a focusing system satisfying the Herschel condition. These spots are distributed symmetrically about the focus on the optical axis with variable positions and intensities. Although we consider only the case of three spherical spots in this paper, generalization to the multiple-spots case will present no difficulty. © 2010 Optical Society of America.
  Accession Number: 20104013272225