We make a detailed analysis on the linearity and accuracy of the relationship between the full-width at half-height (FWHH) of the atmosphere molecules Rayleigh scattering spectrum and the square root of the atmospheric temperature. A simulation of the FWHH of the atmosphere molecules Rayleigh scattering spectrum is made based on the S6 Atmosphere Model and U.S. Standard Atmosphere Model. The calculated temperature is compared with the initial simulation temperature. The result shows that the FWHH of the atmosphere molecules Rayleigh scattering spectrum is nearly proportional to the atmospheric temperature. The goodness-of-fit index of the fitting curve is 0.9977 and the maximum absolute error of measured atmospheric temperature is about 2 K.

By using the closed orbit theory, the photodetachment cross section of H- near a metal surface is derived and calculated. The results show that the metal surface has great influence on the photodetachment process. As the ion-surface distance is very large, the influence of the electrostatic image potential caused by the metal surface becomes small and can be neglected. The period, action, and length of the detached electron’s closed orbit are nearly the same as the case of the photodetachment of H- near an elastic interface. However, with the decrease of the ion-surface distance, the influence of the metal surface becomes significant. The amplitude of the oscillation in the photodetachment cross section becomes complicated. Each resonance peak in the Fourier transformed cross section is associated with one electron’s closed orbit. Unlike the case of the photodetachment of H- near an elastic interface, the length of the closed orbit does not equal the twice distance between the ion and the surface. But with the increase of the ion-surface distance, the length of the closed orbit approaches the case of the closed orbit near an elastic interface, which suggests the correctness of our method. This study provides a new understanding on the photodetachment process of H- in the presence of a metal surface.

We fabricate and measure a multilayer-coated ion-beam-etched laminar grating for the extreme ultraviolet wavelength region. The fabrication process is carefully controlled so that the grating groove and multilayer-coating parameters well meet the design targets. At an incident angle of 10\degree, the peak diffraction efficiency of the +1st order is 20.6% at 14.56 nm and that of the -1st order is 22.1% at 14.65 nm, both close to the theoretical limits.

2 We discuss several kinds of code schemes and analyze their spectral efficiency, code utilizing efficiency, and the maximal spectral efficiency. Error correction coding is used to increase the spectral efficiency, and it can avoid the spectral decrease with the increase of the length. The extended primer code (EPC) has the highest spectral efficiency in the unipolar code system. The bipolar code system has larger spectral efficiency than unipolar code system, but has lower code utilizing efficiency and the maximal spectral efficiency. From the numerical results, we can see that the spectral efficiency increases by 0.025 (b/s)/Hz when the bit error rate (BER) increases from 10^{-1} to 10^{-7}.

Based on Sagnac interferometer, a simple distributed optical fiber sensing system with sub-loop is presented to monitor the vibration applied on the sensing fiber. By introducing a sub-loop, three output beams of interference with different delay time are gotten. Location of the vibration is analyzed through mathematical-physical equations. The vibration frequency, amplitude, and location are theoretically simulated. The results agree well with the previous experiments.

The optical carrier suppression in optical quadruple frequency modulation by cascaded external modulators is investigated theoretically and experimentally. Theoretical analysis demonstrates that the optical carrier suppression ratio is related with not only the initial phase difference of electrical signals applied on the two modulators, but also the optical phase shift between the two modulators. The maximum suppression ratio can be achieved when the total phase difference is equal to n\pi+\pi/2 (n=1,2,...), which is verified by experiments. By properly controlling the total phase shift, 40-GHz millimeter-wave is generated by using a 10-GHz radio frequency (RF) source and the modulators.This work was supported by the National “973" Program of China under Grant No.2006CB302806. E-mail: zw-03@mails.tsinghua.edu.cn1. R. P. Braun, G. Grosskopf, D. Rohde, and F. Schmidt, Electron. Lett. 32, 626 (1996).2. Y. Li, A. J. C. Vieira, S. M. Goldwasser, and P. R. Herczfeld, IEEE Trans. Microwave Theory Techniq. 49, 2048 (2001).3. J. Marti, J. L. Corral, F. Ramos, V. Polo, and J. M. Fuster, Electron. Lett. 35, 517 (1999).4. H. Wen, L. Chen, Y. Pi, J. Yu, and S. Wen, Chinese J. Lasers (in Chinese) 34, 935 (2007).5. M. Bhattacharya, B. Sarkar, and T. Chattopadhyay, IEEE Photon. Technol. Lett. 14, 1611 (2002).6. L. A. Johansson and A. J. Seeds, IEEE Photon. Technol. Lett. 12, 690 (2000).7. D. Wake, C. R. Lima, and P. A. Davies, IEEE Trans. Microwave Theory Techniq. 43, 2270 (1995).8. G. Qi, J. Yao, J. Seregelyi, S. Paquet, and J. C. Bélisle, Proc. SPIE 5579, 598 (2004).9. Q. Ye, R. Qu, and Z. Fang, Chin. Opt. Lett. 5, 8 (2007).10. J. Zhang, H. Chen, M. Chen, T. Wang, and S. Xie, IEEE Photon. Technol. Lett. 19, 1057 (2007).

2 A high sensitive fiber Bragg grating (FBG) strain sensor with automatic temperature compensation is demonstrated. FBG is axially linked with a stick and their free ends are fixed to the measured object. When the measured strain changes, the stick does not change in length, but the FBG does. When the temperature changes, the stick changes in length to pull the FBG to realize temperature compensation. In experiments, 1.45 times strain sensitivity of bare FBG with temperature compensation of less than 0.1 nm Bragg wavelength drift over 100 oC shift is achieved.

The robustness of the software-synchronized all-optical sampling for optical performance monitoring is estimated for 10-Gb/s fiber communication systems. It reveals that the software-synchronized algorithm is sensitive to the signal degradation caused by chromatic dispersion and nonlinearity in optical fibers. The influence of timing jitter and amplitude fluctuation of the sampling pulses is also investigated. It is found that stringent requirements are imposed on the quality of the sampling pulse and the tolerance of 1-dB Q penalty is measured. Considering the practically available optical sampling pulse sources, the results indicate that the amplitude fluctuation of the sampling pulses has the dominant impacts on the software-synchronized method.

A robust view selection algorithm for multiview stereo matching is presented. Different from the existent view selection algorithms which pick only the believable views for matching, this method assigns an adaptive weight to each target view based on the dissimilarity between it and the reference view. So it can utilize the information of all views more sufficiently. The algorithm has been evaluated with different real images to demonstrate its robustness.

We investigate the spectral approaches to the problem of point pattern matching, and present a spectral feature descriptors based on partial least square (PLS). Given keypoints of two images, we define the position similarity matrices respectively, and extract the spectral features from the matrices by PLS, which indicate geometric distribution and inner relationships of the keypoints. Then the keypoints matching is done by bipartite graph matching. The experiments on both synthetic and real-world data corroborate the robustness and invariance of the algorithm.

Infrared images are firstly analyzed using the multifractal theory so that the singularity of each pixel can be extracted from the images. The multifractal spectrum is then estimated, which can reflect overall characteristic of an infrared image. Thus the edge and texture of an infrared image can be accurately extracted based on the singularity of each pixel and the multifractal spectrum. Finally the edge pixels are classified and enhanced in accordance with the sensitivity of human visual system to the edge profile of an infrared image. The experimental results obtained by this approach are compared with those obtained by other methods. It is found that the proposed approach can be used to highlight the edge area of an infrared image to make an infrared image more suitable for observation by human eyes.OCIS code: 100.0100.This work was supported by the Natural Science Foundation of Heilongjiang Province under Grant No.F200818. E-mail: ythaa@163.com1. G. Xia and B. Zhao, Chin. Opt. Lett. 5, 51 (2007).2. G. Wang, L. Xiao, Z. Jiang, Y. Song, and A. He, Acta Opt. Sin. (in Chinese) 26, 1345 (2006).3. T.-L. Ji, M. K. Sundareshan, and H. Roehrig, IEEE Trans. Med. Imaging 13, 573 (1994).4. K. A. Panetta, E. J. Wharton, and S. S. Agaian, IEEE Trans. Syst. Man Cybern. B 38, 174 (2008).5. J. Zhao, C. Yang, and B. Yu, Acta Photon. Sin. (in Chinese) 32, 61 (2003).6. K. Ferens and W. Kinsner, in IEEE WESCANEX ’95 Proceedings 438 (1995).7. I. Reljin, B. Reljin, I. Pavlovic, and I. Rakocevic, in Proceedings of 10th Mediterranean Electrotechnical Conference 2, 490 (2000).8. J. Liu, K. Bowyer, D. Goldgof, and S. Sarkar, in Proceedings of 1997 International Conference on Information, Communications and Signal Processing 170 (1997).9. B. B. Chaudhuri and N. Sarkar, IEEE Trans. Pattern Anal. Mach. Intell. 17, 72 (1995).

Noise reduction is one of the most exciting problems in electronic speckle pattern interferometry. We present a homomorphic partial differential equation filtering method for interferometry fringe patterns. The diffusion speed of the equation is determined based on the fringe density. We test the new method on the computer-simulated fringe pattern and experimentally obtain the fringe pattern, and evaluate its filtering performance. The qualitative and quantitative analysis shows that this technique can filter off the additive and multiplicative noise of the fringe patterns effectively, and avoid blurring high-density fringe. It is more capable of improving the quality of fringe patterns than the classical filtering methods.

A high packing density laser diode stack array is developed utilizing Al-free active region laser bars with a broad waveguide and discrete copper microchannel-cooled heatsinks. The microchannel cooling technology leads to a 10-bar laser diode stack array having the thermal resistance of 0.199 oC/W, and enables the device to be operated under continuous-wave (CW) condition at an output power of 1200 W. The thickness of the discrete copper heatsink is only 1.5 mm, which results in a high packing density and a small bar pitch of 1.8 mm.

We propose a new laser preparation technique to solder Sn-Ag3.5-Cu0.7 on a copper clad laminate (CCL). The experiment is conducted by selective laser heating and melting the thin solder layer and then preprinting it on CCL in order to form the matrix with solder pads. Through the analysis of macro morphology of the matrix with solder pads and microstructure of single pads, this technique is proved to be suitable for preparing solder pads and that the solder pads are of good mechanical properties. The results also reveal that high frequency laser pulse is beneficial to the formation of better solder pad, and that the 12-W fiber laser with a beam diameter of 0.030 mm can solder Sn-Ag3.5-Cu0.7 successfully on CCL at 500-kHz pulse frequency. The optimized parameters of laser soldering on CCL are as follows: the laser power is 12 W, the scanning speed is 1.0 mm/s, the beam diameter is 0.030 mm, the lead-free solder is Sn-Ag3.5-Cu0.7, and the laser pulse frequency is 500 kHz.

A one-dimensional (1D) top-hat, diode-end-pumped, electro-optically Q-switched Nd:YVO4 slab laser is demonstrated. Under the pump power of 175.5 W, 26.3-W output power is obtained with the repetition rate of 5 kHz and the pulse width of 4.3 ns. The output beam has a good top-hat beam profile in both the near field and the far field.

Laser solid forming (LSF) from blended elemental powders is an advanced technique to investigate new alloy systems and to create innovative materials. Accurate composition control is critical for the applications of this technique. In this letter, the composition analysis is performed on LSF titanium alloys from blended Ti, Al, and V powders. It is found that the composition of as-deposited sample can be controlled by keeping the identity of the divergence angle of each elemental powder stream. Based on the consistency condition for divergence angles of different elemental powder streams, the matching relation among the Ti, Al, and V powder characteristics (particle size and density) can be obtained, which ensures the consistency in composition between the laser deposits and the blended elemental powders under different laser processing parameters.

The effect of quantum well number on the quantum efficiency and temperature characteristics of InGaN/GaN laser diodes (LDs) is determined and investigated. The 3-nm-thick In_{0.13}Ga_{0.87}N wells and two 6-nm-thick GaN barriers are selected as an active region for Fabry-Perot (FP) cavity waveguide edge emitting LD. The internal quantum efficiency and internal optical loss coefficient are extracted through the simulation software for single, double, and triple InGaN/GaN quantum wells. The effects of device temperature on the laser threshold current, external differential quantum efficiency (DQE), and output wavelength are also investigated. The external quantum efficiency and characteristic temperature are improved significantly when the quantum well number is two. It is indicated that the laser structures with many quantum wells will suffer from the inhomogeneity of the carrier density within the quantum well itself which affects the LD performance.

We obtain the photonic bands and intrinsic losses for the triangular lattice three-component two-dimensional (2D) photonic crystal (PhC) slabs by expanding the electromagnetic field on the basis of waveguide modes of an effective homogeneous waveguide. The introduction of the third component into the 2D PhC slabs influences the photonic band structure and the intrinsic losses of the system. We examine the dependences of the band gap width and gap edge position on the interlayer dielectric constant and interlayer thickness. It is found that the gap edges shift to lower frequencies and the intrinsic losses of each band decrease with the increasing interlayer thickness or dielectric constant. During the design of the real PhC system, the effect of unintentional native oxide surface layer on the optical properties of 2D PhC slabs has to be taken into consideration. At the same time, intentional oxidization of macroporous PhC structure can be utilized to optimize the design.

The synthesis of zinc oxide (ZnO) nanowires is achieved by vapor phase transportation (VPT) method. The designed quartz tube, whose both ends are narrow and the middle is wider, is used to control the growth of ZnO nanowires. Dielectrophoresis (DEP) method is employed to align and manipulate ZnO nanowires which are ultrasonic dispersed and suspended in ethanol solution. Under the dielectrophoretic force, the nanowires are trapped on the pre-patterned electrodes, and further aligned along the electric field and bridge the electrode gap. The dependence of the alignment yield on the applied voltage and frequency is investigated.

A simple method is adopted to grow ZnO nanofibers laterally among the patterned seeds designed in advance on silicon substrate. The preparation of seed lattices is carried out by lithographing the metal zinc film evaporated on the substrate. A layer of aluminum is covered on the zinc layer to prevent the ZnO nanorods vertically growing on the top surface. After oxidation, the patterned ZnO/Al2O3 spots are formed at the sites for the horizontal growth of ZnO nanofibers by the vapor phase transportation (VPT) method using the zinc powders as source material.

Employing nonlinear spectral imaging technique based on two-photon-excited fluorescence and second-harmonic generation (SHG) of biological tissue, we combine the image-guided spectral analysis method and multi-channel subsequent detection imaging to map and visualize the intrinsic species in a native rabbit aortic wall. A series of recorded nonlinear spectral images excited by a broad range of laser wavelengths (730-910 nm) are used to identify five components in the native rabbit aortic wall, including nicotinamide adenine dinucleotide (NADH), elastic fiber, flavin, porphyrin derivatives, and collagen. Integrating multi-channel subsequent detection imaging technique, the high-resolution, high contrast images of collagen and elastic fiber in the aortic wall are obtained. Our results demonstrate that this method can yield complementary biochemical and morphological information about aortic tissues, which have the potential to determine the tissue pathology associated with mechanical properties of aortic wall and to evaluate the pharmacodynamical studies of vessels.

We present a 1.5-\mum continuous-wave (CW) single-frequency intracavity singly resonant optical parametric oscillator (SRO) based on periodically poled lithium niobate (PPLN). The SRO is placed inside the ring cavity of a single-frequency 1.06-\mum Nd:YVO4 laser pumped by a laser diode. The device delivers a maximum single-frequency output power of 310 mW at a resonant signal wavelength of 1.57 \mum. The signal wave could be tuned from 1.57 to 1.59 \mum by temperature tuning of PPLN crystal over the range of 130-170 oC.

An analysis of splice loss between photonic crystal fibers (PCFs) and conventional single-mode fibers (SMFs) is presented at bending and straight conditions, by using scalar effective index method (SEIM), vectorial effective index method (VEIM), and finite-difference frequency domain (FDFD) methods. It is shown that when there is a slight bending at the vicinity of splice joint, the spot size increases sharply at higher frequencies. On the basis of the obtained results, a mechanism to optimize the splice loss between PCFs and conventional SMFs, both with any geometry, is suggested. The results can be utilized for PCF-based devices to be jointed to SMF as a transmission medium.

We propose a new type of Y-branch power splitter and beam expander with scales of microns in two-dimensional (2D) photonic crystals (PCs) by drilling air holes in a silicon slice. Its functionality and performance are numerically investigated and simulated by finite-difference time-domain (FDTD) method. Simulation results show that the splitter can split a TE polarized light beam into two parallel sub-beams and the distance between them is tunable by changing the parameters of the splitter, while the expander can expand a narrow beam into a wider one, which is realized in an integrated optical circuit. The proposed device is based on the avoiding of anomalous reflection effect and the coupling transmission of defect modes of the interfaces.

By utilizing multimode squeezed states theory, we study the generalized nonlinear equal-power higher-power sum squeezing properties of the generalized magnetic-field component in four-state superposition multimode entangled state light field |\psi^{(4)}>q. The state is composed of multimode vacuum state, multimode coherent state and its contrary state, multimode imaginary coherent state. It is found that the state |\psi^{(4)}>q is a type of four-state superposition multimode nonclassical light field, and under certain fixed conditions, the generalized magnetic-field component in the state |\psi^{(4)}>q can display generalized nonlinear equal-power 4m-th power sum squeezing effects which change periodically.

The optical wave scattering from one-dimensional (1D) lossy dielectric Gaussian random rough surface is studied. The tapered incident wave is introduced into the classical Kirchhoff approximation (KA), and the shadowing effect is also taken into account to make the KA results have a high accuracy. The definition of the bistatic scattering coefficient of the modified KA and the method of moment (MOM) are unified. The characteristics of the optical wave scattering from the lossy dielectric Gaussian random rough surface of different parameters are analyzed by implementing MOM.

The effect of annealing condition on sputtered indium tin oxide (ITO) films on quartz with the thickness of 200 nm is characterized to show enhanced optical transparency and optimized electrical contact resistivity. The as-deposited grown ITO film exhibits only 65% and 80% transmittance at 532 and 632.8 nm, respectively. After annealing at 475 oC for 15 min, the ITO film is refined to show improved transmittance at shorter wavelength region. The transmittances of 88.1% at 532 nm and 90.4% at 632.8 nm can be obtained. The 325-nm transmittance of the post-annealed ITO film is greatly increased from 12.7% to 41.9%. Optimized electrical property can be obtained when annealing below 450 oC, leading to a minimum sheet resistance of 26 \Omega/square. Such an ITO film with enhanced ultraviolet (UV) transmittance has become an alternative candidate for applications in current UV photonic devices. The morphology and conductance of the as-deposited and annealed ITO films are determined by using an atomic force microscopy (AFM), showing a great change on the uniformity distribution with finite improvement on the surface conductance of the ITO film after annealing.