2012
2012
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Record 205 of
Title:Influence of Ag nanoparticles on luminescent performance of SiO 2:Tb3 + nanomaterials
Author(s):Zhang, Dekai(1,2); Hu, Xiaoyun(1,2); Ji, Ruonan(1); Zhan, Suchang(1); Gao, Jianhua(1,2); Yan, Zhiyun(1); Liu, Enzhou(3); Fan, Jun(3); Hou, Xun(1,4)Source: Journal of Non-Crystalline Solids Volume: 358 Issue: 20 DOI: 10.1016/j.jnoncrysol.2012.07.004 Published: October 1, 2012Abstract:Tb3 + single-doped SiO2 (SiO2:Tb 3 +) and Tb3 +, Ag co-doped SiO2 (SiO 2:Tb3 +-Ag) nanostructured luminescent materials were prepared by a modified St?ber method. Their microstructure and optical property were investigated using scanning electron microscopy, ultraviolet visible absorption and photoluminescence spectrophotometry. Results show that the samples are composed of well-dispersed near-spherical particles with a diameter about 50 nm, the highest fluorescence intensity is obtained when the doping concentration of Tb3 + is 4.86 mol%, the corresponding internal quantum efficiency is 13.6% and the external quantum efficiency is 8.2%. The experimental results indicate that Ag nanoparticles can greatly enhance the light absorption at 226 nm and the light emission at 543 nm of SiO2:Tb3 +-Ag, and the fluorescence lifetime reduces with increasing Ag concentration in SiO2:Tb3 +-Ag. Additionally, the present results indicate that fluorescence enhancement is attributed to the local field enhancement and the increased radiative decay rates induced by Ag nanoparticles. ? 2012 Elsevier B.V.Accession Number: 20123715436571 -
Record 206 of
Title:Characteristics of pulse evolution in mode-locked thulium-doped fiber laser
Author(s):An, Ying(1,2); Shen, Deyuan(1); Zhao, Wei(1); Long, Jingyu(1)Source: Optics Communications Volume: 285 Issue: 7 DOI: 10.1016/j.optcom.2011.12.001 Published: April 1, 2012Abstract:We have numerically investigated the characteristics of the pulse evolution in a passively mode-locked thulium-doped fiber laser with net anomalous cavity dispersion. For the fixed resonator configuration, single-, dual-, triple-, and quadruple-pulses are generated successively by enhancing the pump power or reducing the output ratio. The characteristics of the single or multiple pulses are investigated with various cavity lengths. The separation between the two coexisting pulses changes with the pump power due to the interaction between the soliton and the dispersive waves, and then the two randomly distributed pulses could finally evolve into a soliton pair with fixed separation. According to the results of the numerical simulation, the multiple pulses are found to be generated via pulse splitting and the pulse splitting threshold decreases with the increase of the cavity length. ? 2011 Elsevier B.V. All rights reserved.Accession Number: 20120514725858 -
Record 207 of
Title:Hollow-core photonic bandgap fiber with microfluid-infiltrated air holes for slow-light propagation
Author(s):Ren, Liyong(1); Liang, Jian(1,2); Yun, Maojin(2)Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 8497 Issue: DOI: 10.1117/12.929124 Published: 2012Abstract:Slow light plays an important role in the fields of all-optical signal processing and integration photonics. It has shown many potential applications, such as realizing optical delay lines or buffers, enhancing linear and nonlinear light-matter interactions, as well as increasing the sensitivity of the interferometers and transducers. In this paper, hollow-core photonic bandgap fibers made from high index glasses are designed by infiltrating microfluid into the air-holes to tailor the fiber dispersion for slow-light propagation under low pulse distortion. In such a fiber made from Si material, group index ng~8 is obtained with a bandwidth up to 30 nm, where the group index fluctuation is restricted in ±10 % of the ng, while ng~6 is obtained with a bandwidth over 100 nm when the chalcogenide material is selected instead. Such a ±10 % criterion determines a regarded flatland region accordingly, and in this region the group velocity dispersion can be negligible. It is found that for the same fiber length the slow-light time delay in the photonic bandgap fiber is much larger as compared with that in the single mode fiber. This kind of photonic bandgap fiber may have many potential applications in short-distance fiber communications and delay lines. ? 2012 SPIE.Accession Number: 20130415935026 -
Record 208 of
Title:Numerical investigation of soliton molecules with variable separation in passively mode-locked fiber lasers
Author(s):Li, Xiaohui(1,2); Wang, Yishan(1); Zhao, Wei(1); Zhang, Wei(1); Hu, Xiaohong(1); Gao, Cunxiao(1); Zhang, Han(3); Yang, Zhi(1); Wang, Hushan(1); Wang, Xianglin(1); Li, Cheng(1); Shen, Deyuan(1)Source: Optics Communications Volume: 285 Issue: 6 DOI: 10.1016/j.optcom.2011.11.052 Published: March 15, 2012Abstract:Soliton molecules evolution is numerically investigated in a passively mode-locked fiber laser based on the nonlinear polarization rotation (NPR) technique. Peak-to-peak separation of soliton molecules can be controlled by changing either pump strength or cavity linear phase delay appropriately. Moreover, soliton molecules with intensity-independent evolution, separation-independent evolution and large intensity-vibrating evolution are numerically found, respectively. The characteristics of soliton molecules evolution versus linear phase delay or pump strength are given. Periodic stable evolution regimes are found. The separation-controllable soliton molecules can be attributed to the mutual effects of phase delay, Kerr nonlinearity and other parameters of the cavity.? 2011 Elsevier B.V. All rights reserved.Accession Number: 20120314701901 -
Record 209 of
Title:Incremental threshold learning for classifier selection
Author(s):Pang, Yanwei(1); Deng, Junping(1); Yuan, Yuan(2)Source: Neurocomputing Volume: 89 Issue: DOI: 10.1016/j.neucom.2012.01.012 Published: July 15, 2012Abstract:Threshold-based classifier is a simple yet powerful pattern classification tool, which has been frequently used in applications of object detection and recognition. A threshold-based classifier is usually associated with a unique one-dimensional feature. A properly selected threshold and a binary sign corresponding to the feature govern the classifier. However, the learning process is usually done in a batch manner. The batch algorithms are not suitable for sequentially incoming data because of the limitation of storage and prohibitive computation cost. To deal with sequentially incoming data, this paper proposes an incremental algorithm for incrementally learning the threshold-based classifiers. The proposed method can not only incrementally model the features but also estimate the threshold and training error in a close form. The effectiveness of the proposed algorithm is evaluated in the applications of gender recognition, face detection, and human detection. ? 2012 Elsevier B.V.Accession Number: 20121814980589 -
Record 210 of
Title:Detection of electromagnetic pulse induced hazard on electroexplosive device based on optical-fiber fluorescence
Author(s):Liu, Lan-Shu(1,2); Zhang, Wen-Song(1); Zhu, Xiang-Ping(1)Source: Advanced Materials Research Volume: 383-390 Issue: DOI: 10.4028/www.scientific.net/AMR.383-390.7492 Published: 2012Abstract:The electroexplosive devices(EED) are widely used in the core system of rocket, missile and nuclear weapons. Hazard analysis and measurement of electromagnetic pulse is of great importance to the security and reliability of EED. In this article, an optical-fiber fluorescence temperature sensor is proposed for analyzing hazard induced by electromagnetic pulse of EED. The temperature of EED can be measured through the fluorescence lifetime, then the induced current is obtained, and thereby the electromagnetic pulse induced hazard can be draw. The experiments show that, the set-up of this proposal can works with high precision and fast response, and immune to the electromagnetic interference.Accession Number: 20115114623295 -
Record 211 of
Title:Decoding algorithms for improving the imaging performance of Vernier anode readout
Author(s):Yan, Qiurong(1,2); Zhao, Baosheng(1); Yang, Hao(1,2); Liu, Yong'an(1); Sheng, Lizhi(1,2); Wei, Yonglin(1); Sai, Xiaofeng(1)Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 8332 Issue: DOI: 10.1117/12.917036 Published: 2012Abstract:The Long Slit Spectrograph is one of instruments onboard The World Space Observatory-Ultraviolet. Both the FUV (102-1700nm) and NUV (160-320nm) channels of LSS choose micro-channel plates (MCP) detector with anode readout in the focal plane. The MCP detectors with anode readout are typically used to provide photon counting imaging. According to the desired performance of LSS, the Vernier anode may be the optimum readout scheme. The Vernier anode is famous for its high spatial resolution, however, the original decode algorithms of the Vernier anode is susceptible to wrongly decode, when the charge acquisition is not precise enough and the footprint size of charge cloud collected by Vernier anode is not small enough and eventually results in the deterioration of photon counting image. In this paper, the causes leading to image deterioration is analyzed. The least-squares method was used to calculate the phase value to correct imaging distortions caused by charge measurement accuracy. The area ratio of each electrode covered by charge cloud is accurately calculated to improving the imaging results. The corrected algorithms are verified by experimental results and the results show that the correction methods can obviously improve the quality of the original photon counting image. ? 2012 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE).Accession Number: 20121514939423 -
Record 212 of
Title:Ultra-wideband high-power pulse source based on pulse coupling
Author(s):Gou, Yongsheng(1,2); Liu, Baiyu(1); Ruan, Chi(1); Bai, Yonglin(1); Zhang, Wei(1,2); Bai, Xiaohong(1); Qin, Junjun(1); Yang, Wenzheng(1); Wang, Bo(1)Source: Hongwai yu Jiguang Gongcheng/Infrared and Laser Engineering Volume: 41 Issue: 2 DOI: Published: February 2012Abstract:Based on solid state semiconductor devices and transistor avalanche theories of ultra-fast electronics, with pulse coupled method, multi-channel high-voltage picoseconds pulses were coupled in the time domain, and the ultra-wideband, high-pulse was obtained. The feasibility of the design was confirmed by four-channel pulse coupling experiment with the result of the output pulse power was increased. The experiment with amplitude of 1.33 kV, pulse width of 770 ps and jitter of less than 1% are generated by MARX circuits firstly. After the four pulses coupled, the output pulse will be with 2.66 kV, 875 ps and less than 1% in amplitude, width and jitter, respectively. This method can be extended to multi-channel pulse coupling to obtain higher power.Accession Number: 20121514940922 -
Record 213 of
Title:Electric field distribution characteristics of photoconductive antennas
Author(s):Zou, Sheng-Wu(1,2); Zhang, Tong-Yi(1)Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 8419 Issue: DOI: 10.1117/12.956431 Published: 2012Abstract:Photoexcitation of biased semiconductor photoconductive antennas by femtosecond pulses is the most common and convenient technique for generating strong terahertz (THz) pulses. In this paper, we use the three-dimensional (3D) finite-difference-time-domain (FDTD) to analyze electric field distribution of THz pulses in the near-field from a photoconductive antenna. The simulation is based on solving Maxwell's equations and the carrier rate equations simultaneously on realistic dipole antenna structures. The 3D FDTD simulation gives detailed features of THz electric field distribution in and out of the antenna. It is found that the difference of near-field distribution between the substrate and free space is considerably large. The fields of the alternating-current dipole exhibit an unsymmetrical distribution and a large deviation from those calculated using the simple Hertzian dipole theory. The magnitude of THz field in and out of the substrate attenuates rapidly while it holds the line in the gap center. The high-frequency components of THz radiation emission come only from the dipole antenna, while the low-frequency components are from both the center electrodes and coplanar stripline waveguide. This work can be used to optimize the design of antenna geometry and raise the radiation field power. ? 2012 SPIE.Accession Number: 20131416168306 -
Record 214 of
Title:High-peak-power, single-mode, nanosecond pulsed, all-fiber laser for high resolution 3D imaging LIDAR system
Author(s):Yun, Jian(1,2); Gao, Cunxiao(1); Zhu, Shaolan(1); Sun, Chuandong(1); He, Haodong(1); Feng, Li(1); Dong, Lijun(1,2); Niu, Linquan(1,2)Source: Chinese Optics Letters Volume: 10 Issue: 12 DOI: 10.3788/COL201210.121402 Published: December 2012Abstract:This study presents an eye-safe, single-mode, nanosecond-pulsed, and all-fiber laser source with masteroscillator-power-amplifier configuration at 1 550 nm that is suitable for high-resolution three-dimensional (3D) imaging light detection and ranging (LIDAR) system. The output peak power of 7.6 kW is obtained at the 1.2-ns pulse width and 50-kHz repetition rate. The single-mode pulse laser output ensures the range precision and imaging results of the LIDAR system. The laser is used as a transmitter for the 3D imaging LIDAR system. The detailed characteristics of the LIDAR system and the results of the 3D imaging are presented. ? 2012 Chinese Optics Letters.Accession Number: 20131516200492 -
Record 215 of
Title:Fast computation for generating CGH of a 3D object by employing connections between layers
Author(s):Tang, Chuang(1,2); Yao, Baoli(1)Source: Journal of Modern Optics Volume: 59 Issue: 16 DOI: 10.1080/09500340.2012.715691 Published: September 20, 2012Abstract:An approximate method for generating computer-generated holograms (CGH) of a 3D object with six times faster speed than the conventional algorithm is presented. In the conventional algorithm, a 3D object is sliced into many layers and treated as a collection of self-illuminated point light source. The propagation process of a light ray from every point of an object to all the points on the hologram plane is simulated and interfered with by the reference beam to form a CGH. In our proposed method, under the assumption that the depth of a 3D object is much smaller than the recording distance, we just need to calculate the oblique distance between the first layer and the hologram plane, and then the oblique distances from the other layers to the hologram plane can be obtained from a simple relation, thus the computational time is much reduced. The CGH is optically reconstructed and the quality of the reconstructed image agrees well with that from the conventional algorithm. ? 2012 Copyright Taylor and Francis Group, LLC.Accession Number: 20124215585139 -
Record 216 of
Title:Analysis and study of the interlaced encoding pixels in Hadamard transform spectral imager based on DMD
Author(s):Xu, Jun(1,2); Hu, Bingliang(1); Feng, Dazheng(3); Fan, Xiaohui(4); Qian, Qingming(1,2)Source: Optics and Lasers in Engineering Volume: 50 Issue: 3 DOI: 10.1016/j.optlaseng.2011.10.007 Published: March 2012Abstract:The key innovation in Hadamard transform spectral imager (HTSI) introduced recently is the use of digital micro-mirror device (DMD) to encode spectral information. However, because the size of individual micro-mirrors does not match the detector pixel size or for other unavoidable errors in the optical design and the system assembling, an interlaced encoding phenomenon appears on some pixels of the encoded images obtained from the detector. These interlaced encoding pixels are not encoded based on Hadamard transform, so they should be processed specially in spectrum recovery. This paper analyzes the interlaced encoding phenomenon and proposes a positioning method and a decoding method for the interlaced encoding pixels on the encoded images. In our experiment, we direct a beam of laser into our HTSI and fill the entire field of view; by observing the column vector, which is made up of the gray values of a pixel on the encoded images from the detector in sequence, the interlaced encoding pixels can be distinguished easily and a coefficient is obtained simultaneously, which denotes the ratio of the area between the left part and the right part of the interlaced encoding pixel. By substituting the coefficient and the encoded gray values of the interlaced pixel into its encoding equation, we can recover the spectral elements of the interlaced pixel with ease. By comparing the spectral curve of the interlaced encoding pixels recovered by the method mentioned in this paper and the spectral curves of its two adjacent pixels, we find the decoding results are quite effective. ? 2011 Elsevier Ltd. All rights reserved.Accession Number: 20115214636607