黄色一级网线,一级aaa久久

2011

Record 169 of

Title:Millijoule pulse energy picosecond fiber chirped-pulse amplification system

Author(s):Yang, Zhi(1,2); Hu, Xiaohong(1); Wang, Yishan(1); Zhang, Wei(1); Zhao, Wei(1)
Source: Chinese Optics Letters Volume: 9 Issue: 4 DOI: 10.3788/COL201109.041401 Published: April 2011
Abstract:The efficient generation of a 1.17-mJ laser pulse with 360 ps duration using an ytterbium (Yb)-doped fiber amplifier chain seeded by a homemade mode-locked fiber laser is demonstrated experimentally. A specially designed figure-of-eight fiber laser acts as the seed source of a chirped-pulse amplification (CPA) system and generates mode-locked pulses with hundreds of picosecond widths. Two kinds of large-mode-area (LMA) double-clad Yb-doped fibers are employed to construct the pre-amplifier and main amplifier. All of the adopted instruments help avoid severe nonlinearity in fibers to raise sub-nanosecond pulse energy with acceptable signal-to-noise ratio (SNR). The output spectrum of this fiber-based CPA system shows that amplified spontaneous emission (ASE) is suppressed to better than 30 dB, and the onset of stimulated Raman scattering is excluded. ? 2011 Chinese Optics Letters.
Accession Number: 20112114001760
Record 170 of

Title:Improvement of the performance of the twisted-nematic liquid-crystal display as a phase modulator

Author(s):Ma, Baiheng(1,2); Yao, Baoli(1); Li, Ze(1,2); Ye, Tong(1)
Source: Applied Optics Volume: 50 Issue: 17 DOI: 10.1364/AO.50.002588 Published: June 10, 2011
Abstract:A twisted-nematic liquid-crystal display (TN-LCD) placed between two linear polarizers (P) generally produces coupled intensity and phase modulations. For the purpose of phase-only modulation, quarter- wave plates (QWPs) are often used in front of or behind the LCD. In this paper, we demonstrate theoretically and experimentally the QWPs' effect on the modulation properties of the TN-LCD based on the general Jones matrix descriptions for all the devices, which circumvents the inconvenience of the traditional method on the basis of the TN-LCD's internal parameters. We prove that the phase modulation depth of the TN-LCD can be further increased in the configuration of P1-QWP 1-LCD-QWP2-P2 with each component properly oriented, provided that the mean intensity transmission is decreased to a lower level. By observing the diffracted patterns of the Ronchi phase grating or blazed grating addressed onto the TN-LCD, we verify the validity of the proposed method. Improved reconstructed image quality from the kinoformloaded on the TN-LCD is obtained in this configuration. This approach is valuable when the TN-LCD is employed as a phase modulator, especially for the modern, thinner TN-LCD. ? 2011 Optical Society of America.
Accession Number: 20112514069706
Record 171 of

Title:A new processing way for helicoid reflective mirror

Author(s):Hu, Shaolei(1,2); Xie, Yongjun(1); Zhao, Xin(1,2)
Source: Advanced Materials Research Volume: 314-316 Issue: DOI: 10.4028/www.scientific.net/AMR.314-316.94 Published: 2011
Abstract:A novel processing way for the continuous helicoid reflective mirrors is proposed. We use an intelligent oven to accurately control the glass temperature and successfully produce a helicoid reflective mirror in B270 glass. Then we test the shape and optical properties of the helicod reflective mirror via the three-coordinate instrument measuring and interference experiment. ? (2011) Trans Tech Publications, Switzerland.
Accession Number: 20113914365094
Record 172 of

Title:Effects of beam misalignment on space laser communication systems

Author(s):Lu, Hongqiang(1,2); Zhao, Wei(1); Hu, Hui(1); Wang, Wei(1); Xie, Xiaoping(1)
Source: Qiangjiguang Yu Lizishu/High Power Laser and Particle Beams Volume: 23 Issue: 4 DOI: 10.3788/HPLPB20112304.0895 Published: April 2011
Abstract:In order to predict and estimate the effects of atmospheric turbulence, vibration of terminals and misalignment on space laser communication, the amplitude of detected signals changing with lateral offset (between the center of the focused beam and the center of the photodetector in the detecting plane and defocus (between the detecting plane and the focal plane, are calculated in simulation and measured in experiment, and the fit error rate(BER), signal-to-noise ratio and jitter of the detected signals changing with lateral offset and defocus are also measured. The results show that the performance of space laser communication systems would deteriorate significantly as the lateral offset and defocus increase, and the lateral offset has more effect. The maximum defocus and lateral offset permitted are 1 mm and 0.03 mm, respectively, with the experimental parameters, when the BER of communication changes from 10-10 to 10-5.
Accession Number: 20112214017105
Record 173 of

Title:Reflective point-diffraction microscopic interferometer with long-term stability

Author(s):Guo, Rongli(1,2); Yao, Baoli(1); Gao, Peng(1); Min, Junwei(1); Zheng, Juanjuan(1); Ye, Tong(1)
Source: Chinese Optics Letters Volume: 9 Issue: 12 DOI: 10.3788/COL201109.120002 Published: December 2011
Abstract:An on-axis phase-shifting reflective point-diffraction microscopic interferometer for quantitative phase microscopy based on Michelson architecture is proposed. A cube beamsplitter splits the object wave spectrum into two copies within two arms. Reference wave is rebuilt in one arm by low-pass filtering on the object wave frequency spectrum with a pinhole-mask mirror, and interferes with the object wave from the other arm. Polarization phase-shifting is performed and phase imaging on microscale specimens is implemented. The experimental results demonstrate that the proposed scheme has the advantage of long-term stability due to its quasi common-path geometry with full use of laser energy. ? 2011 Chinese Optics Letters.
Accession Number: 20120214676543
Record 174 of

Title:Femtosecond electron pulse compression by using the time focusing technique in ultrafast electron diffraction

Author(s):Wen, Wen-Long(1); Lei, Xiao-Hong(1,2); Hu, Xin(3); Xu, Xiang-Yan(1); Wang, Jun-Feng(1); Cao, Xi-Bin(1); Liu, Hu-Lin(1); Wang, Chao(1); Dang, Li-Hong(4); Tian, Jin-Shou(1)
Source: Chinese Physics B Volume: 20 Issue: 11 DOI: 10.1088/1674-1056/20/11/114102 Published: November 2011
Abstract:We present a new model of an electron gun for generating subrelativistic femtosecond (fs) electron pulses. The basic idea is to utilize a dc acceleration stage combined with a time focusing region, the time focusing electrode generates an electron energy chirp for bunching at the target. Without considering the space charge effects, simulations of the electron gun were carried out under the conditions of different dc voltages and various slopes of the voltage added on the time focusing electrode. Tracing and simulating large numbers of photoelectrons through Monte - Carlo and finite difference methods, the electron pulses with 1 ps can be compressed to 55 fs, which will allow significant advances in the field of ultrafast diagnosis. ? 2011 Chinese Physical Society and IOP Publishing Ltd.
Accession Number: 20114814562850
Record 175 of

Title:A technology to generate arbitrary electrical waveform for shaping high power laser

Author(s):Liu, H.(1,2); Liu, B.-Y.(1); Bai, Y.-L.(1); Gou, Y.-S.(1); Zheng, J.-K.(1,2)
Source: Journal of Electromagnetic Waves and Applications Volume: 25 Issue: 4 DOI: 10.1163/156939311794500287 Published: January 1, 2011
Abstract:In order to improve the output power of laser pulse in the inertia confinement fusion experiment, an arbitrary waveform generator is fabricated to shape the laser pulse. The arbitrary waveform generator is based on the micro-strip line transmission delay technology and GaAs Field Effect Transistor set which has a good ability of generating voltage-controlled current. To satisfy high amplitude requirement on electrical pulse for optical waveguide modulator, an ultra-broad bandwidth voltage tunable amplifier is applied to the output signals, and the pulse amplitude is adjustable. The designed generator generates a pulse waveform with amplitude between 0 and 5 V, duration less than 10 ns, 330 ps time-domain adjustment and a square pulse with rising edge 471 ps, falling edge 428 ps. The experiment results show the shaped laser pulse is obtained based on the shaping electrical pulse. ? 2011 VSP.
Accession Number: 20110713659495
Record 176 of

Title:Preliminary study of zinc ion sensor with the function of imaging

Author(s):Wang, Jian(1,2); Wang, Li-Li(2)
Source: Guang Pu Xue Yu Guang Pu Fen Xi/Spectroscopy and Spectral Analysis Volume: 31 Issue: 11 DOI: 10.3964/j.issn.1000-0593(2011)11-3145-05 Published: November 2011
Abstract:A zinc ion fluorescence sensor with imaging was fabricated by using 1-(2-Pyridylazo)-2-naphthol and fluorescent reagent of rhodamine B together as the indication which was immobilized on an tip of gradient index lens by base catalyzed sol-gel method. Combined with improved metallographic microscope and laser, the measurement of zinc ion concentration and the view of sample morphology could be ealized simultaneously by this system. The sensor has the linear range of zinc ion concentration from 0.1 to 1 mmol · L-1. Moreover, it has the capabilities of imaging with the whole system's resolution of 18.73 lp · mm-1. This sensor with the function of imaging has the potential applications in biosensing.
Accession Number: 20114614524957
Record 177 of

Title:Properties of photon counting imaging detector with Au photocathode

Author(s):Liu, Yongan(1); Zhao, Feifei(1,2); Hu, Huijun(1,2); Sheng, Lizhi(1); Yan, Qiurong(1); Zhao, Baosheng(1)
Source: Guangxue Xuebao/Acta Optica Sinica Volume: 31 Issue: 1 DOI: 10.3788/AOS20113101.0123002 Published: January 2011
Abstract:Au photocathode is used in photon counting imaging system with induction readout. A 15 nm gold film is deposited on the resolution test board and it is used for transmission photocathode. The gain performance of micro-channel plates (MCP), resolution and counting rate of the detector with Au photocathode are tested. The results show that the system with Au cathode has a quasi-Gaussian pulse height distribution (PHD) curves. The peak of the PHD curves moved to the high-gain zone and the full width at half maximum (FWHM) gradually widened as the voltage increased. After the adoption of Au cathode, the detection efficiency and the signal-to-noise ratio of photon counting imaging detector effectively improved. The resolution test results show that the spatial resolution of the detector is better than 75 μm, and the counting rate can reach 13.5 kHz when the system's resolution is better than 150 μm.
Accession Number: 20111213768089
Record 178 of

Title:Optimization of the high repetition rate all-fiber two-stage ytterbium-doped fiber amplifier

Author(s):Yun, Jian(1,2); Gao, Cunxiao(1,2); Zhu, Shaolan(1,2); Sun, Chuandong(1,2); Dong, Lijun(2)
Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 8198 Issue: DOI: 10.1117/12.917087 Published: 2011
Abstract:Based on the technique of master oscillator power amplifier (MOPA), a two-stage ytterbium-doped fiber amplifier (YDFA) with all-fiber structure is theoretically simulated. The seed signal operating at the wavelength of 1064 nm has the characteristic of high repetition rate (10 MHz), ultrashort pulse duration (10 ps), low signal power input (20μW) and single longitudinal mode. The gain (and amplification stimulation emission power) is calculated at the different pump powers and gain fiber lengths of YDFA pumped by 975 nm. In addition, the amplifications at the different signal power inputs (1-25μW) are also simulated. The numerical results can be used to optimize the YDFA. ? 2011 SPIE.
Accession Number: 20120314692799
Record 179 of

Title:Detection and fitting of pulse profile for x-ray pulsar navigation system

Author(s):Chen, Baomei(1,2); Zhao, Baosheng(1); Hu, Huijun(1,2); Sheng, Lizhi(1,2); Yan, Qiurong(1,2)
Source: Guangxue Xuebao/Acta Optica Sinica Volume: 31 Issue: 5 DOI: 10.3788/AOS201131.0534002 Published: May 2011
Abstract:Several new methods to improve the time accuracy and resolution based on the original X pulsar navigation ground simulation system are proposed. By these proposed methods, the accuracy and real-time performance of the spacecraft navigation has been enhanced. The methods adopted include: 1) enhancing the performance of the photon counting detector based on micro-channel plate (MCP); 2) using time measurement system with high accuracy. The pulse profile of the original detection system is compared with the pulse profile of the improved detection system, and the gain of MCP which has influence on the detected pulse profile is discussed. The experimental results show that the counting rate of improved detection system becomes higher under the same experimental condition. When the operating voltage of MCP is-800 V in the improved detection system, and the value of Bin is 1.5 ms, a pulse profile with good signal-to-noise ratio (SNR) can be acquired after being integrated for 200 s.
Accession Number: 20112314043575
Record 180 of

Title:Universal no reference image quality assessment metrics based on local dependency

Author(s):Gao, Fei(1); Gao, Xinbo(1); Tao, Dacheng(2); Li, Xuelong(3); He, Lihuo(1); Lu, Wen(1)
Source: 1st Asian Conference on Pattern Recognition, ACPR 2011 Volume: Issue: DOI: 10.1109/ACPR.2011.6166657 Published: 2011
Abstract:No reference image quality assessment (NR-IQA) is to evaluate image quality blindly without the ground truth. Most of the emerging NR-IQA algorithms are only effective for some specific distortion. Universal metrics that can work for various categories of distortions have hardly been explored, and the algorithms available are not fully adequate in performance. In this paper, we study the local dependency (LD) characteristic of natural images, and propose two universal NR-IQA metrics: LD global scheme (LD-GS) and LD two-step scheme (LD-TS). We claim that the local dependency characteristic among wavelet coefficients is disturbed by various distortion processes, and the disturbances are strongly correlated to image qualities. Experimental results on LIVE database II demonstrate that both the proposed metrics are highly consistent with the human perception and outpace the state-of-the-art NR-IQA indexes and some full reference quality indicators for diverse distortions and across the entire database. ? 2011 IEEE.
Accession Number: 20122715188560

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