2011
2011
-
Record 157 of
Title:Slightly off-axis interferometry for microscopy with second wavelength assistance
Author(s):Han, Junhe(1); Gao, Peng(2); Yao, Baoli(2); Gu, Yuzong(1); Huang, Mingju(1)Source: Applied Optics Volume: 50 Issue: 17 DOI: 10.1364/AO.50.002793 Published: June 10, 2011Abstract:Slightly off-axis interferometry for microscopy has been performed, where the dc term of the interferogram is suppressed by the object wave in another wavelength. One wavelength of the laser beam (red light) is used to generate the slightly off-axis interferogram, while the second wavelength (blue light) is employed to measure the transmittance of the specimen. Both the red light and blue light are recorded simultaneously by a color CCD camera and can be separated without cross talk via the red-green-blue components. The dc term of the slightly off-axis interferogram of red light is suppressed with the object wave of blue light. As a consequence, the requirement on the off-axis angle between the object and reference waves is relaxed as well as the requirement on the resolving power of CCD camera. ? 2011 Optical Society of America.Accession Number: 20112514069704 -
Record 158 of
Title:Influence of spectral broadening on femtosecond wavelength conversion based on four-wave mixing in silicon waveguides
Author(s):Wang, Zhaolu(1,2); Liu, Hongjun(1); Huang, Nan(1); Sun, Qibing(1); Wen, Jin(1,2)Source: Applied Optics Volume: 50 Issue: 28 DOI: 10.1364/AO.50.005430 Published: October 1, 2011Abstract:Femtosecond wavelength conversion in the telecommunication bands via four-wave mixing in a 1:5mm long silicon rib waveguide is theoretically investigated. Compared with picosecond pulses, the spectra are greatly broadened for the femtosecond pulses due to self-phase modulation and cross-phase modulation in the four-wave mixing process, and it is difficult to achieve a wavelength converter when the pump and signal pulse widths are close to or less than 100 fs in the telecommunication bands because of the spectral overlap. The influence of the spectral broadening on the conversion efficiency is also investigated. The conversion bandwidth of 220nm and peak conversion efficiency of -8 dB are demonstrated by using 500 fs pulses with higher efficiency than the picosecond pulse-pumped efficiency when the repetition rate is 100 GHz. ? 2011 Optical Society of America.Accession Number: 20114014404955 -
Record 159 of
Title:High-speed dynamic spectrum data acquisition system based on linear CCD
Author(s):Zheng, Jinkun(1,2); Bai, Yonglin(1); Wang, Bo(1); Liu, Baiyu(1); Gou, Yongsheng(1); Liu, Hui(1,2)Source: Chinese Optics Letters Volume: 9 Issue: SUPPL. 1 DOI: 10.3788/COL201109.S10308 Published: June 2011Abstract:High-speed dynamic spectrum data of transient detection has become the major means of access to transient information. However, in terms of the characteristic of spectral data excessiveness and transience in the dynamic spectral detection system, the linear charge-coupled device (CCD) used in the system should have real-time-output and match the high-speed data storage equipment. Based on the transient spectrum characteristic, we introduce a high-speed dynamic spectrum data acquisition system with a high-linear array CCD. Through the field of programming gate array, the system provides an accurate driving clock for CCD and generates the control signals for analog-to-digital (A/D) conversion, storage, and transmission. Finally, the collected data by the peripheral component interconnect bus are summarized and filtered in the host computer. The results show that the CCD can stably work with a 40-MHz clock, and the frame scanning frequency can achieve 73 KHz. This design can remarkably complete the real-time measurement of the denotation transient temperature and achieve high-speed spectral information collection and storage with high accuracy and frame scanning frequency. It can be applied to other transient information acquisition. ? 2011 Chinese Optics Letters.Accession Number: 20113214224378 -
Record 160 of
Title:Imaging properties of a tetra wedge readout
Author(s):Liu, Yong-An(1); Yan, Qiu-Rong(1); Sai, Xiao-Feng(1); Wei, Yong-Lin(1); Sheng, Li-Zhi(1,2); Hu, Hui-Jun(1,2); Zhao, Bao-Sheng(1)Source: Chinese Physics B Volume: 20 Issue: 6 DOI: 10.1088/1674-1056/20/6/068503 Published: June 2011Abstract:The decoding principle of a tetra wedge anode, which is a development of the wedge and strip anode, is described. The influence of charge cloud size on decoding accuracy is studied using the Monte Carlo method. Simulation results show that the decoding error is large when the size of charge clouds collected by the anode is small. Thus, the charge clouds collected by the tetra wedge anode should reach a necessary size to ensure accurate decoding. Finally, using the ultraviolet photon counting imaging system, the linearity and the spatial resolution of the system are tested. Experimental results show that the system has a good linearity and the spatial resolution is better than 100 μm. ? 2011 Chinese Physical Society and IOP Publishing Ltd.Accession Number: 20112414068567 -
Record 161 of
Title:Decoding algorithms of single photon counting imager based on two-dimensional Vernier anodes
Author(s):Yang, Hao(1,2); Zhao, Baosheng(1); Yan, Qiurong(1); Liu, Yongan(1); Hu, Huijun(1,2)Source: Science China: Physics, Mechanics and Astronomy Volume: 54 Issue: 11 DOI: 10.1007/s11433-011-4490-y Published: November 2011Abstract:The decoding algorithms of two-dimensional Vernier anodes are deduced theoretically. The precision of decoding and uniqueness of encoding are proved. The influencing factors of detection sensitivity and spatial resolution are discussed. The single photon imaging system is constructed, and the two-dimensional Vernier collector is fabricated. The image of the ultra-weak emission source is reconstructed. The spatial resolution of the system is about 100 μm. ? 2011 Science China Press and Springer-Verlag Berlin Heidelberg.Accession Number: 20114814572243 -
Record 162 of
Title:X-ray photon-counting detector based on a micro-channel plate for pulsar navigation
Author(s):Chen, Baomei(1,2); Zhao, Baosheng(1); Hu, Huijun(1,2); Yan, Qiurong(1,2); Sheng, Lizhi(1,2)Source: Chinese Optics Letters Volume: 9 Issue: 6 DOI: 10.3788/COL201109.060401 Published: June 2011Abstract:The pulse time of arrival (TOA) is a determining parameter for accurate timing and positioning in X-ray pulsar navigation. The pulse TOA can be calculated by comparing the measured arrival time with the predicted arrival time of the X-ray pulse for pulsar. In this study, in order to research the measurement of pulse arrival time, an experimental system is set up. The experimental system comprises a simulator of the X-ray pulsar, an X-ray detector, a time-measurement system, and a data-processing system. An X-ray detector base is proposed on the basis of the micro-channel plate (MCP), which is sensitive to soft X-ray in the 1-10 keV band. The MCP-based detector, the structure and principle of the experimental system, and results of the pulse profile are described in detail. In addition, a discussion of the effects of different X-ray pulse periods and the quantum efficiency of the detector on pulse-profile signal-to-noise ratio (SNR) is presented. Experimental results reveal that the SNR of the measured pulse profile becomes enhanced as the quantum efficiency of the detector increases. The SNR of the pulse profile is higher when the period of the pulse is smaller at the same integral. ? 2011 Chinese Optics Letters.Accession Number: 20112714124397 -
Record 163 of
Title:Study on the circuit producing high-speed pulse with high peak current
Author(s):Yan, Deke(1,2); Gou, Yongsheng(1,2); Song, Zhiyuan(1,2); Sun, Chuandong(1); Zhu, Shaolan(1)Source: Chinese Optics Letters Volume: 9 Issue: SUPPL. 1 DOI: 10.3788/COL201109.S10307 Published: June 2011Abstract:To achieve high peak current with narrow pulse width, the circuit model is analyzed based on a fast and high-power metallic oxide semiconductor field effecttransistor (MOSFET) as the high speed switch of the resistor-capacitor (RC) charge and discharge circuits. It is easy to obtain a narrow high-current pulse by adopting the narrow triggering pulse to control the on-off state of the MOSFET switch, and using the driving pulse to modulate the exponential decay pulse in the RC discharge loop. The procedure for the high speed MOSFET switch is then discussed. To make the speed of the MOSFET switch as quick as possible, the push-pull driving circuit for the grid of the MOSFET is brought forward and the circuit for producing the narrow trigger pulse is designed. The experimental result shows that the full width at half maximum (FWHM) of the trigger pulse is about 500 ps when the narrow trigger pulse is connected with the discharge return circuit. Measured results demonstrate that the RC discharge loop produces a narrow high-current pulse, with a peak current of up to 92.5 A and FWHM of 6.2 ns. After adjusting relevant parameters, the peak current could reach up to 115.9 A. However, the corresponding pulse width is broadened. Finally, influencing factors on the narrow pulse width for the discharge loop are briefly analyzed. ? 2011 Chinese Optics Letters.Accession Number: 20113214224377 -
Record 164 of
Title:Spectral characteristics of chirped fiber Bragg gratings in large-mode-area fibers
Author(s):Zhao, Baoyin(1,2); Duan, Kailiang(1); Zhao, Wei(1)Source: Qiangjiguang Yu Lizishu/High Power Laser and Particle Beams Volume: 23 Issue: 7 DOI: 10.3788/HPLPB20112307.1794 Published: July 2011Abstract:A matrix method is extended to solve the multimode coupling differential equations, and thereby the spectral characteristics of the chirped Bragg gratings in large-mode-area fibers (LMA FBGs) are studied theoretically. Unlike those of Bragg gratings in single mode optical fibers (SM FBGs), the reflection spectra of chirped LMA FBGs contain self-coupling and co-coupling peaks of the existing modes. For the chirped LMA FBGs, the reflectivity decreases and the reflection peaks split. These splits can be improved on some degree by Gaussian apodization function.Accession Number: 20113614310384 -
Record 165 of
Title:Partially supervised neighbor embedding for example-based image super-resolution
Author(s):Zhang, Kaibing(1); Gao, Xinbo(1); Li, Xuelong(2); Tao, Dacheng(3)Source: IEEE Journal on Selected Topics in Signal Processing Volume: 5 Issue: 2 DOI: 10.1109/JSTSP.2010.2048606 Published: April 2011Abstract:Neighbor embedding algorithm has been widely used in example-based super-resolution reconstruction from a single frame, which makes the assumption that neighbor patches embedded are contained in a single manifold. However, it is not always true for complicated texture structure. In this paper, we believe that textures may be contained in multiple manifolds, corresponding to classes. Under this assumption, we present a novel example-based image super-resolution reconstruction algorithm with clustering and supervised neighbor embedding (CSNE). First, a class predictor for low-resolution (LR) patches is learnt by an unsupervised Gaussian mixture model. Then by utilizing class label information of each patch, a supervised neighbor embedding is used to estimate high-resolution (HR) patches corresponding to LR patches. The experimental results show that the proposed method can achieve a better recovery of LR comparing with other simple schemes using neighbor embedding. ? 2010 IEEE.Accession Number: 20111313857082 -
Record 166 of
Title:Applications of digital if receivers and under-sampling technique in ladar
Author(s):Song, Zhi-Yuan(1,2); Zhu, Shao-Lan(1); Dong, Li-Jun(1,2); Feng, Li(1); He, Hao-Dong(1)Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 8192 Issue: DOI: 10.1117/12.901928 Published: 2011Abstract:The traditional technique of phase laser range finder is mixing high frequency signals with analog circuits and filtering them to obtain the useful signal with low frequency. But the analog mixing circuits are susceptible to interference and will bring amplitude attenuation, phase jitter and offset and this way has difficulties in achieving high precision ranging and fast speed ranging at the same time. The method of this paper is based on under-sampling technique with digital synchronous detection and referring to Digital down converter technique of digital IF receiver in radar system. This method not only reduces the complexity of data processing, improves the speed and accuracy of phase detection at the same time, but also reduces requirements for ADC devices and DSP chips in the ladar system by a lower sampling rate. At the same time, the structure of electronic system is global simplified compared with traditional analog ladar system and the anti-jamming is greatly enhanced. So this method has important research value. ? 2011 SPIE.Accession Number: 20113714320244 -
Record 167 of
Title:Influence of modulation depth errors on properties of apodized chirped fiber Bragg grating property
Author(s):Yang, Lin(1,2); Duan, Kailiang(2); Luo, Shirong(1); Zhao, Wei(2)Source: Qiangjiguang Yu Lizishu/High Power Laser and Particle Beams Volume: 23 Issue: 2 DOI: 10.3788/HPLPB20112302.0308 Published: February 2011Abstract:Starting from the coupled mode equations, the influence of modulation depth errors on the properties of apodized chirped fiber Bragg grating(ACFBG) is investigated theoretically by using a matrix method. The results show that the errors of low frequency distribution deteriorate the performance of ACFBG much more than the errors of high frequency distribution with the same amplitude level, and the errors of higher amplitude level lead to more performance degradation. Therefore, errors of both low frequency distribution and high amplitude level should be avoided in the fabrication of the fiber grating.Accession Number: 20111413897786 -
Record 168 of
Title:Analysis of birefringent and dispersive properties of photonic crystal fibers
Author(s):Lu, S.(1,2); Li, W.(1); Guo, H.(1); Lu, M.(1)Source: Applied Optics Volume: 50 Issue: 30 DOI: 10.1364/AO.50.005798 Published: October 20, 2011Abstract:Two types of high birefringence photonic crystal fiber (PCF) which import four or six big circular air holes near the elliptical-hole are proposed. Their birefringent and dispersive properties are analyzed by full-vector finite-element method (FEM). Numerical analysis demonstrates that importing the big circular hole near the center of elliptical-hole PCFs can achieve a high birefringence. When the ratio (d= Λ) of diameter to hole spacing is larger than 0.8, the proposed two types of PCF have a larger birefringence than that of sole elliptical air hole ones. When the ratio d=Λ is equal to 0.95, the birefringences of these two types PCF can be as high as 4:27 × 10?3 and 5:09 × 10?3 at the wavelength of 1:55 μ m, respectively. Besides, PCF with the four big circular air holes has a large negative dispersion at the long wavelength in x-polarized mode, which indicates a potential in single-polarized mode dispersion compensation. ? 2011 Optical Society of America.Accession Number: 20114414470004