2012

• Record 313 of
  
  Title:Steady-state multiple dark photovoltaic spatial solitons
  
  Author(s):Zhang, Y.H.(1,2); Lu, K.Q.(2); Guo, J.B.(2); Li, K.H.(2); Liu, B.Y.(1)
  Source: European Physical Journal D  Volume: 66  Issue: 3  DOI: 10.1140/epjd/e2012-20560-4  Published: March 2012  
  Abstract:We theoretically study the formation of the steady state multiple dark photovoltaic spatial solitons in the photovoltaic photorefractive crystal under open-circuit conditions. The results indicate that the initial dark notch width at the entrance face of the crystal is a key parameter for generating an even (or odd) number sequence of multiple dark photovoltaic solitons. The dark notch is generated from a phase or amplitude discontinuity in the center of the input beam. If the initial width of the dark notch is small, only a fundamental soliton or a Y-junction soliton is generated. As the initial width of the dark notch is increased, the dark notch tends to split into an odd (or even) number of multiple dark photovoltaic solitons, realizing a progressive transition from a lower-order soliton to the higher-order multiple solitons. When the multiple dark photovoltaic solitons are generated, the separations between adjacent dark solitons become smaller. Solitons pairs become progressively wider and less visible as their transverse distance from the central dark soliton increases and they move away from each other as they propagate in the photorefractive nonlinear crystal. © EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2012.
  Accession Number: 20214611172432
• Record 314 of
  
  Title:High-power semiconductor laser array packaged on microchannel cooler using gold-tin soldering technology
  
  Author(s):Wang, Jingwei(1); Kang, Lijun(1); Zhang, Pu(2); Nie, Zhiqiang(2); Li, Xiaoning(2); Xiong, Lingling(2); Liu, Xingsheng(1,2)
  Source: Proceedings of SPIE - The International Society for Optical Engineering  Volume: 8241  Issue:   DOI: 10.1117/12.909655  Published: 2012  
  Abstract:High power semiconductor laser arrays have found increased applications in many fields. In this work, a hard soldering microchannel cooler (HSMCC) technology was developed for packaging high power diode laser array. Numerical simulations of the thermal behavior characteristics of hard solder and indium solder MCC-packaged diode lasers were conducted and analyzed. Based on the simulated results, a series of high power HSMCC packaged diode laser arrays were fabricated and characterized. The test and statistical results indicated that under the same output power the HSMCC packaged laser bar has lower smile and high reliability in comparison with the conventional copper MCC packaged laser bar using indium soldering technology. © 2012 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE).
  Accession Number: 20121014830330
• Record 315 of
  
  Title:Manufacture of lasers with multiple operating modes
  
  Author(s):Zhu, Changjun(1); Xue, Bing(1); Zhai, Xuejun(1); He, Junfang(2)
  Source: Advanced Materials Research  Volume: 482-484  Issue:   DOI: 10.4028/www.scientific.net/AMR.482-484.1937  Published: 2012  
  Abstract:A two-beam pumped Ti:sapphire laser with femtosecond and picosecond cavities was manufactured. Three operating modes, independent self mode-locking, cross mode-locking and multi-pulse operating, were achieved. In the independent self mode-locking mode, femtosecond and picosecond laser pulses were generated in the two cavities, respectively. In the cross mode-locking mode, synchronized femtosecond and picosecond laser pulses were obtained in the two cavities. In the multi-pulse mode, multi-pulses were produced in the picosecond cavity. The results show that, the independent self mode-locking mode is dominated mainly by group velocity dispersion and self-phase modulation, the cross mode-locking mode is governed primarily by cross-phase modulation and the multi-pulse operating is ruled largely by self-amplitude modulation. © (2012) Trans Tech Publications, Switzerland.
  Accession Number: 20121414922952
• Record 316 of
  
  Title:Analysis of temporal broadening of optical pulses by atmospheric dispersion in laser communication system
  
  Author(s):Lu, Hongqiang(1,2); Zhao, Wei(1); Xie, Xiaoping(1)
  Source: Optics Communications  Volume: 285  Issue: 13-14  DOI: 10.1016/j.optcom.2012.02.094  Published: June 15, 2012  
  Abstract:In this paper, pulse broadening caused by atmospheric dispersion is analyzed, which is the key factor in high-speed and long-distance free space laser communication systems according to our simulation. The measured datum of atmospheric parameters, including atmospheric pressure and atmospheric temperature of the desert in Xinjiang, China, is used in the analysis of pulses broadening. The pulse broadening caused by atmospheric dispersion is very significant when pulsewidth is on the order of 5 ps, and pulse broadening is negligible if the pulsewidth is larger than 20 ps. With the increment of optical wavelength, atmospheric dispersion-induced pulse broadening is mitigated. The received pulsewidth is dominated mainly by dispersion-induced pulse broadening at small duty ratio of original signal, and original pulsewidth at large duty ratio of original signal respectively. By selecting proper duty ratio of optical pulse, the received pulsewidth can be minimized and the system bit rate can be maximized. © 2012 Elsevier B.V. All rights reserved.
  Accession Number: 20121614954744
• Record 317 of
  
  Title:A probabilistic model for image representation via multiple patterns
  
  Author(s):Li, Jun(1); Tao, Dacheng(1); Li, Xuelong(2)
  Source: Pattern Recognition  Volume: 45  Issue: 11  DOI: 10.1016/j.patcog.2012.04.021  Published: November 2012  
  Abstract:For image analysis, an important extension to principal component analysis (PCA) is to treat an image as multiple samples, which helps alleviate the small sample size problem. Various schemes of transforming an image to multiple samples have been proposed. Although having been shown effective in practice, the schemes are mainly based on heuristics and experience. In this paper, we propose a probabilistic PCA model, in which we explicitly represent the transformation scheme and incorporate the scheme as a stochastic component of the model. Therefore fitting the model automatically learns the transformation. Moreover, the learned model allows us to distinguish regions that can be well described by the PCA model from those that need further treatment. Experiments on synthetic images and face data sets demonstrate the properties and utility of the proposed model. © 2012 Elsevier Ltd. All rights reserved.
  Accession Number: 20122515126285
• Record 318 of
  
  Title:Stable passively Q-switched operation of Tm3+ doped silica fiber laser by anti-resonant fabry-perot saturable absorber
  
  Author(s):Long, J.Y.(1); Shen, D.Y.(1); Wang, Y.Sh.(1); Zhao, W.(1); An, Y.(1); Zhou, W.(1,2)
  Source: Laser Physics  Volume: 22  Issue: 5  DOI: 10.1134/S1054660X12050209  Published: May 2012  
  Abstract:We demonstrate a diode-pumped passively Q-switched Tm-doped double-cladding silica fiber laser operating at wavelength of 1960 nm using an anti-resonant Fabry-Perot saturable absorber as passive modulation element. To determine a relatively preferable fiber length for stable cw Q-switched operation, three active fiber simples with the length of 1.1, 5.3, and 7.0 m were employed respectively in our experiments. With 1.1 m gain fiber, we generated Q-switched pulses with a pulse width of 245 ns and an average power of up to 2.2 W at a repetition rate of 620 kHz. For the longer two fiber samples, Q-switched operation with longer pulse duration, Q-switched mode-locking and cw mode-locking were observed, respectively. © Pleiades Publishing, Ltd., 2012.
  Accession Number: 20122115046037
• Record 319 of
  
  Title:Collimating lens for light-emitting-diode light source based on non-imaging optics
  
  Author(s):Wang, Guangzhen(1,2); Wang, Lili(1); Li, Fuli(2); Zhang, Gongjian(2)
  Source: Applied Optics  Volume: 51  Issue: 11  DOI: 10.1364/AO.51.001654  Published: April 10, 2012  
  Abstract:A collimating lens for a light-emitting-diode (LED) light source is an essential device widely used in lighting engineering. Lens surfaces are calculated by geometrical optics and nonimaging optics. This design progress does not rely on any software optimization and any complex iterative process. This method can be used for any type of light source not only Lambertian. The theoretical model is based on point source. But the practical LED source has a certain size. So in the simulation, an LED chip whose size is 1 mm* 1 mm* is used to verify the feasibility of the model. The mean results show that the lenses have a very compact structure and good collimating performance. Efficiency is defined as the ratio of the flux in the illuminated plane to the flux from LED source without considering the lens material transmission. Just investigating the loss in the designed lens surfaces, the two types of lenses have high efficiencies of more than 90% and 99%, respectively. Most lighting area (possessing 80% flux) radii are no more than 5 m when the illuminated plane is 200 m away from the light source. © 2012 Optical Society of America.
  Accession Number: 20121614947810
• Record 320 of
  
  Title:Modeling and testing of static pressure within an optical fiber cable spool using distributed fiber Bragg gratings
  
  Author(s):Ma, Chengju(1,2); Ren, Liyong(1); Qu, Enshi(1); Tang, Feng(3); Liang, Quan(3)
  Source: Optics Communications  Volume: 285  Issue: 24  DOI: 10.1016/j.optcom.2012.07.064  Published: November 1, 2012  
  Abstract:Based on the force analysis, we establish a theoretical model to study the static pressure distribution of the fiber cable spool for the fiber optic guided missile (FOG-M). Simulations indicate that for each fiber layer in the fiber cable spool, the applied static pressure on it asymptotically converges as the number of fiber layers increases. Using the distributed fiber Bragg grating (FBG) sensing technique, the static pressure of fiber cable layers in the spool on the cable winding device was measured. Experiments show that the Bragg wavelength of FBG in every layer varies very quickly at the beginning and then becomes gently as the subsequent fiber cable was twisted onto the spool layer by layer. Theoretical simulations agree qualitatively with experimental results. This technology provides us a real-time method to monitor the pressure within the fiber cable layer during the cable winding process. © 2012 Elsevier B.V. All rights reserved.
  Accession Number: 20124315591054
• Record 321 of
  
  Title:Slow-light element for tunable time delay based on optical microcoil resonator
  
  Author(s):Ma, Chengju(1,2); Ren, Liyong(1); Xu, Yiping(1)
  Source: Applied Optics  Volume: 51  Issue: 26  DOI: 10.1364/AO.51.006295  Published: September 10, 2012  
  Abstract:We propose a simple and compact slow-light element by use of an optical microcoil resonator (OMR) constituted by two microfiber coils. Based on the matrix exponential method, we solve the coupled-wave equations of the OMR with n turns of microfiber coils and obtain a general solution. Simulations indicate that a tunable slow-light propagation can be obtained by controlling the coupling coefficient between the two adjacent microfiber coils by means of regulating the voltage applied to the ferroelectric crystal. A slow-light time delay up to 62 ps with a bandwidth of 0.4 nm is performed at the wavelength around 1.5 μm. © 2012 Optical Society of America.
  Accession Number: 20123915463679
• Record 322 of
  
  Title:Design of wideband, high-resolution optical waveform samplers based on a dispersion-flattened highly nonlinear photonic crystal fiber
  
  Author(s):Liu, Yuanshan(1); Zhang, Jian-Guo(1,2); Zhao, Wei(1)
  Source: Journal of Optics  Volume: 14  Issue: 5  DOI: 10.1088/2040-8978/14/5/055201  Published: May 2012  
  Abstract:A novel scheme is proposed for ultrafast optical waveform samplers capable of operating over a wide wavelength range, which uses the four-wave mixing in a highly nonlinear photonic crystal fiber (HNL-PCF) with low and very flat dispersion in the S, C and L bands. We report the first demonstration of the designed optical sampler by employing a 20m dispersion-flattened HNL-PCF for observing the 160Gbits-1 optical data signal to achieve a temporal resolution of less than 0.8ps for a wavelength separation up to 11nm between data signal and sampling lights. This preliminary result is mainly restricted by the tunable optical bandpass filter used in our present experiment. The proposed scheme shows a potential for realizing wideband, high-resolution optical waveform sampling systems in a simple configuration and a cost-effective manner by using commercially available optical fibers of short length. © 2012 IOP Publishing Ltd.
  Accession Number: 20121714959367
• Record 323 of
  
  Title:Analysis and study of static pressure distribution in an optical cable spool using distributed fiber Bragg gratings
  
  Author(s):Ren, Liyong(1); Ma, Chengju(1,2); Tang, Feng(3); Qu, Enshi(1); Han, Xu(1)
  Source: Proceedings of SPIE - The International Society for Optical Engineering  Volume: 8351  Issue:   DOI: 10.1117/12.913783  Published: 2012  
  Abstract:We present a theoretical model to study the static pressure distribution among the layers of an optical fiber cable spool based on the force analysis of the cable system. Using the distributed fiber Bragg grating (FBG) sensing technique, the static pressures within the fiber cable layers of the spool were measured according to the Bragg wavelength shifts of the FBGs embedded in the cable. The effects of the cable spool shrinkage owing to the pressure from outer fiber cable layers on the cable tension and the radial pressure were analyzed in detail. As a result, the relationship between the static pressure upon the fiber and the resulted Bragg wavelength shift of the FBG was deduced. The static pressure distribution of the fiber optical cable spool is obtained both in theory and experiment. Theoretical simulations coincide with experimental results. This technology provides us a real-time method to monitor the inner pressure among the fiber cable layers during the optical cable winding process. © 2011 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE).
  Accession Number: 20120814779255
• Record 324 of
  
  Title:Formation of multiple dark photovoltaic spatial solitons
  
  Author(s):Zhang, Yuhong(1,2); Lu, Keqing(1); Guo, Jianbang(1); Long, Xuewen(1); Hu, Xiaohong(1); Li, Kehao(1)
  Source: Pramana - Journal of Physics  Volume: 78  Issue: 2  DOI: 10.1007/s12043-011-0226-9  Published: February 2012  
  Abstract:We theoretically study the formation of multiple dark photovoltaic soliton splitting in the quasi-steady-state and steady-state regimes under open-circuit conditions. We find that the initial width of the dark notch at the entrance face of the crystal is a key parameter for generating an even (or odd) number sequence of dark coherent photovoltaic solitons. If the initial width of the dark notch is small, only a fundamental soliton or Y-junction soliton pair is generated. As the initial width of the dark notch is increased, the dark notch tends to split into an odd (or even) number of multiple dark photovoltaic solitons, which realizes a progressive transition from a low-order soliton to a sequence of higher-order solitons. The soliton pairs far away from the centre have bigger width and less visibility. In addition, when the distance from the centre of the dark notch increases, the separations between adjacent dark stripes become slightly smaller. © Indian Academy of Sciences.
  Accession Number: 20120914821287