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2014

Record 445 of

Title:Efficient optical Kerr gating property of fluorotellurite glass

Author(s):Xiong, Yaobing(1); Yan, Lihe(1,2); Zhou, Zhiguang(2); Yi, Wenhui(1); Lin, Aoxiang(2); Si, Jinhai(1); Chen, Feng(1); Hou, Xun(1)
Source: Optik Volume: 125 Issue: 3 DOI: 10.1016/j.ijleo.2013.09.016 Published: February 2014
Abstract:We investigated the ultrafast optical Kerr effect of the fluorotellurite glass (Ft glass), the nonlinear response time of which was measured to be less than 230 fs, while the nonlinear refractive index was estimated to be 9.62 × 10-16 cm2/W. Using optical Kerr gate (OKG) technique with Ft glass as Kerr medium, we obtained narrow-bandwidth and symmetric gated spectra from a supercontinuum (SC) generated by a femtosecond laser. Experimental results indicated that Ft glass was a good candidate for an OKG medium due to its fast response time, large nonlinearity, and high transparency. ? 2013 Elsevier GmbH.
Accession Number: 20135017067711
Record 446 of

Title:Effect of femtosecond laser parameters on TiC ceramic micro-hole drilling

Author(s):Wang, Yuqian(1); Zhang, Junzhan(1); Liu, Yongsheng(2); Yang, Xiaojun(3); Li, Weinan(3); Wang, Chunhui(2)
Source: Zhongguo Jiguang/Chinese Journal of Lasers Volume: 41 Issue: 10 DOI: 10.3788/CJL201441.1003010 Published: October 10, 2014
Abstract:Drilling micro-holes in TiC ceramic with femtosecond laser in different laser fluence and assisted gas pressure has been demonstrated. Scanning electron microscope (SEM), micrometer X-ray 3D imaging system (Micro-CT) and X-ray photoelectron spectroscopy (XPS) are used to investigate the morphology and chemical bonds of micro-holes. The results show that the circularities of micro-holes at the entry are not less than 99% when the laser fluence varies. The circularities of micro-holes at the exit increase as the laser fluence grows, then it tend to be stable. The maximum value of the circularity at the exit is 95%. The taper of micro-holes increases with the assisted gas pressure. When the laser fluence is 0.51 J/mm2, the taper of micro-holes drilled with 0.3 MPa gas pressure is the best, its long axis taper is -0.13° and the short axis taper is 0.77°. C-C bonds and Ti-C bonds rupture while debris which contains metal Ti, Ti2O3 and TiO2 forms around the micro-holes during laser drilling. Lastly, the mechanism of interactions between laser beam and materials is discussed.
Accession Number: 20144600200373
Record 447 of

Title:Group sparse reconstruction for image segmentation

Author(s):Lu, Xiaoqiang(1); Li, Xuelong(1)
Source: Neurocomputing Volume: 136 Issue: DOI: 10.1016/j.neucom.2014.01.034 Published: July 20, 2014
Abstract:Image segmentation is a fundamental problem in computer vision and image analysis. Specially, the segmentation of medical images can assist doctors in making decisions. Due to the lack of distinctive features to describe the boundary of an organ and match function with high performance for features, medical image segmentation is difficult to be achieved with high accuracy. In this paper, an one-class classifier is proposed as the match function to decide whether the pixel belongs to the boundary or not. The proposed method is comprised of two steps. At first, a feature vector space is built with the gradient feature and its statistical information in the training stage. In the test image, a feature vector of one candidate probably being located on the boundary is reconstructed by sparse coding with the feature vector space. After reconstruction, the candidate is classified belonging to boundary or non-boundary via the reconstruction based one-class classifier. Then, in order to maintain the consistency between the candidates which are neighbors to each other, the neighboring candidates are coded using group lasso with the same dictionary. Compared to the traditional methods, the proposed one has three advantages. Firstly, it solves the non-Gaussian distribution problem of the positive samples. Secondly, it avoids large variation among the negative samples. Thirdly, the relationship of the neighboring candidates is considered and used in classification, which is ignored in other methods. The proposed method is validated on 52 MR images of prostate and outperforms Mahalanobis distance, which is considered as one of the state-of-the-art match functions. The experimental results show that the segmentation accuracy can be significantly improved by the proposed method with one-class classification. ? 2014 Elsevier B.V.
Accession Number: 20141517568666
Record 448 of

Title:Temperature control system for SLD optical source of FOCS

Author(s):Cao, Hui(1,2); Yang, Yifeng(1); Liu, Shangbo(1); Xu, Jintao(1); Zhao, Wei(1)
Source: Hongwai yu Jiguang Gongcheng/Infrared and Laser Engineering Volume: 43 Issue: 3 DOI: Published: March 2014
Abstract:To lower the influence of optical source temperature property on the precision of fiber optic current sensor(FOCS) in high voltage grid, an analog temperature control system was proposed to control the optical source working temperature. According to the designed goal, design process of each key section was introduced. A proper temperature signal bridge was analyzed which could obtain a linear relationship between the output differential voltage and temperature. The mathematical model of the system was established in the frequency domain; the transfer function of the system was calculated; and the parameters of proportional-integral-derivative (PID) controller were analyzed in the time domain. A temperature controller used for FOCS super luminescent diode (SLD) optical source was designed, which was verified by fixed temperature test and temperature cycle test. The results show that by means of the real time temperature control, the accuracy of FOCS is up to 0.2 level which reaches industry requirements.
Accession Number: 20142217774745
Record 449 of

Title:Polarization-sensitive diffractive optical elements fabricated in BR films with femtosecond laser

Author(s):Yu, Xianghua(1); Yao, Baoli(1); Lei, Ming(1); Hampp, Norbert(2); Liang, Yansheng(1); Dan, Dan(1); Yang, Yanlong(1); Yan, Shaohui(1); Gao, Peng(1); Ye, Tong(1)
Source: Applied Physics B: Lasers and Optics Volume: 115 Issue: 3 DOI: 10.1007/s00340-013-5611-2 Published: June 2014
Abstract:Multi-photon product (F540-state) of bacteriorhodopsin (BR) polymeric films excited by femtosecond laser shows permanently photoinduced birefringence and dichroism. Based on this property, polarization-sensitive diffractive optical elements (PDOEs), e.g., gratings, two-dimensional optical lattice, Bessel zone plate, were firstly fabricated and investigated in BR films by femtosecond laser multi-beam interference with rotationally symmetric pyramid lenses. These fabricated PDOEs are completely stable at room temperature. The dependence of diffraction efficiency on the incident polarization state was measured. The micro-structures of PDOEs were observed under polarization microscope, and the selective readout diffraction patterns from the polarization-multiplexed PDOEs were demonstrated. ? 2013 Springer-Verlag Berlin Heidelberg.
Accession Number: 20142717888268
Record 450 of

Title:High-resolution reconstruction for terahertz imaging

Author(s):Xu, Li-Min(1,2); Fan, Wen-Hui(1); Liu, Jia(1,2)
Source: Applied Optics Volume: 53 Issue: 33 DOI: 10.1364/AO.53.007891 Published: November 20, 2014
Abstract:We present a high-resolution (HR) reconstruction model and algorithms for terahertz imaging, taking advantage of super-resolution methodology and algorithms. The algorithms used include projection onto a convex sets approach, iterative backprojection approach, Lucy-Richardson iteration, and 2D wavelet decomposition reconstruction. Using the first two HR reconstruction methods, we successfully obtain HR terahertz images with improved definition and lower noise from four low-resolution (LR) 22 × 24 terahertz images taken from our homemade THz-TDS system at the same experimental conditions with 1.0 mm pixel. Using the last two HR reconstruction methods, we transform one relatively LR terahertz image to a HR terahertz image with decreased noise. This indicates potential application of HR reconstruction methods in terahertz imaging with pulsed and continuous wave terahertz sources. ? 2014 Optical Society of America.
Accession Number: 20144800264322
Record 451 of

Title:Resolution and visibility of two-color pseudothermal lensless ghost imaging

Author(s):Xue, Yu-Lang(1,2); Wan, Ren-Gang(1); Feng, Fei(1,2); Zhang, Tong-Yi(1)
Source: Optik Volume: 125 Issue: 16 DOI: 10.1016/j.ijleo.2014.02.029 Published: August 2014
Abstract:Two-color (or nondegenerate-wavelength) lensless ghost imaging using pseudothermal light source is investigated theoretically by use of classical optical coherence theory. We find that for two-color pseudothermal lensless ghost imaging the visibility and resolution is determined by (Δ) the product of the wavelength and the corresponding path length rather than the wavelength for each path or the path length. We also confirm our theoretical conclusion by numerical simulations. The result shows we must make a trade-off between resolution and visibility in devise practical experiments, as the resolution of the imaging can be improved by decreasing Δ but with visibility getting poor, and vice versa. ? 2014 Elsevier GmbH. All rights reserved.
Accession Number: 20143218021762
Record 452 of

Title:Method for enhancing visibility of hazy images based on polarimetric imaging

Author(s):Liang, Jian(1,2); Ren, Liyong(1); Qu, Enshi(1); Hu, Bingliang(1); Wang, Yingli(1)
Source: Photonics Research Volume: 2 Issue: 1 DOI: 10.1364/PRJ.2.000038 Published: 2014
Abstract:A novel polarimetric dehazing method is proposed based on three linear polarization images (0°, 45°, and 90°). The polarization orientation angle of the light scattered by the haze particles is introduced in the algorithm. No additional image-processing algorithm is needed in the postprocessing. It is found that the dehazed image suffers from little noise and the details of the objects close to the observer can be preserved well. In addition, this algorithm is also proved to be useful for preserving image colors. Experimental results demonstrate that such an algorithm has some universality in handling all kinds of haze. We think that this robust algorithm might be very suitable for real-time dehazing. ? 2014 Chinese Laser Press.
Accession Number: 20182705409174
Record 453 of

Title:Study on an ultrathin terahertz multiband metamaterial absorber

Author(s):Chen, Xu(1); Fan, Wenhui(2)
Source: International Symposium on Ultrafast Phenomena and Terahertz Waves, ISUPTW 2014 Volume: Issue: DOI: 10.1364/isuptw.2014.ps_s2s2_p13 Published: October 13, 2014
Abstract:null
Accession Number: 20151900832459
Record 454 of

Title:Conversion efficiency of photon enhanced thermionic emission solar converters with exponential doping GaAs cathodes

Author(s):Tang, Wei-Dong(1,2); Yang, Wen-Zheng(1); Yang, Yang(1,2); Sun, Chuan-Dong(1); Cai, Zhi-Peng(1,2)
Source: Guangzi Xuebao/Acta Photonica Sinica Volume: 43 Issue: 6 DOI: 10.3788/gzxb20144306.0625002 Published: June 2014
Abstract:Photon-enhanced thermionic emission solar energy converter is a new highly efficient solar energy utilization technologies. An exponential doping GaAs material was presented as the cathode of photon-enhanced thermionic emission solar converter. The conversion efficiencies of the photon-enhanced thermionic emission solar devices with exponential doping GaAs were theoretically analyzed by using the energy-balance and diffusion-drift-emission models. The results show that exponential doping GaAs prominently enhances photon-enhanced thermionic emission conversion, and the efficiency of photon-enhanced thermionic emission solar converters with exponential doping GaAs cathodes is a monotonically increasing function of sun concentration and a monotonically decreasing function of cathode surface recombination velocities. The efficiency of the converter can reach 30% at a flux concentration larger than 200 suns and surface recombination velocities maintained at fewer than 104 cm/s.
Accession Number: 20142917959997
Record 455 of

Title:System design and research of Yb:YAG thin disk laser with direct cooling arrangement

Author(s):Song, Qiong-Ge(1,2); Cheng, Guang-Hua(1); Bai, Jing(1); Liu, Xin(1); Tang, Wen-Long(1)
Source: Guangzi Xuebao/Acta Photonica Sinica Volume: 43 Issue: 10 DOI: 10.3788/gzxb20144310.1014001 Published: October 1, 2014
Abstract:A Yb:YAG thin disk laser with a novel four-pass pumped structure and direct water cooling device was designed. The multi-mode pump radiation was from a fiber-coupled 940 nm diode laser. The Yb:YAG disk with 10 mm diameter and 500 μm thickness was employed. The Yb3+ atom fraction was 10%. The direct cooling arrangement was put forward, tap water was contacted with the Yb:YAG through a V groove. The four-pass pump coupling system was well designed with a pair of rectangular prism and a focusing lens which had a diameter of 50 mm and focus of 50 mm. Then simulated the stability of the resonator and calculated the radius of the laser spot in different position of the resonator with the different cavity length. Different types of laser cavity were set up. With the output coupling rate of 5%, the maximum output power of 3.28 W at 1 031 nm was obtained in F-P resonator. The beam quality Mx2=1.79, My2=1.86. The slope efficiency was 20.5%.
Accession Number: 20144700217732
Record 456 of

Title:A test system for infrared focal plane arrays based on LabVIEW

Author(s):Yaohong, Chen(1); Wei, Liu(1); Long, Ren(1); Bo, Yi(1); Qingsheng, Xie(1); Zefeng, Wang(1)
Source: Proceedings - 2014 4th International Conference on Instrumentation and Measurement, Computer, Communication and Control, IMCCC 2014 Volume: Issue: DOI: 10.1109/IMCCC.2014.205 Published: December 22, 2014
Abstract:Most existing test system for infrared focal plane arrays are dedicated, it costly and the application value are limited. A test method for infrared focal plane arrays is introduced in this paper, and test system includes driving circuit, control module, data acquiring and processing circuit, video synthesis module and the PC software based on LabVIEW is established, which measures the key parameters such as responsivity, NETD, non-effective pixels and nonhomogeneity of the conventional polysilicon uncooled infrared focal plane arrays, generate testing report automatically at last. The simple and reliable test system adapted to many devices with different resolution and package, possess excellent universal property and practical value at very low cost. ? 2014 IEEE.
Accession Number: 20150500470172

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