2007, 5(5) Column
Chinese Optics Letters 第5卷 第5期
The optical-optical double-resonant multiphoton ionization (OODR-MPI) spectrum of NO2 molecule in the 460-605 nm wavelength region of the probe photon is presented. The mechanism of the OODR-MPI of NO2 molecule is analyzed. The results show that the resonant features can be assigned to the transitions from the first 3s'sigma'g Rydberg intermediate resonant state to the final np'sigma'u Rydberg series. The ionization pathway is NO2(X2A1)-[3h'nu'1]->3s'sigma'g-[h'nu'2]->np'sigma'u-[h'nu'2 or autoionization]->NO2(+)+e. It is found that the converging potential of the np'sigma'u Rydberg series and the quantum defect of np orbit about NO2 are (78803+-14) cm^(-1) and 0.652+-0.014, respectively. The bending vibration frequency of 5p'sigma'u state is determined also.
光学-光学双色双共振多光子离化 二氧化氮 里德堡序列 离化机制 260.5210 Photoionization 020.4180 Multiphoton processes Transmission characteristics of an excited-state induced dispersion optical filter of rubidium at 775.9 nmDownload:759次
The operation of an ultra-narrow bandwidth optical filter based on the 5P_(3/2)-->5D_(3/2) excited-state transition in rubidium vapor is reported. The 5D_(3/2) state is excited by a circularly polarized pump beam at 780 nm from a diode laser. The filter displays a single 398-MHz bandwidth at a peak transmission of 9.0%, which is narrower than the Doppler bandwidth. The dependence of peak transmission on the pump intensity and cell temperature is also given.
激光感生色散光学滤波器 超窄带带宽 铷 120.2440 Filters 300.6210 Spectroscopy, atomic 300.2530 Fluorescence, laser-induced 020.4180 Multiphoton processes We describe a simple and cost-effective holographic method for the fabrication of surface-relief zone plates. The zone plate is inscribed by interference between the first- and second-order diffracted waves from an ion-etched Fresnel zone plate. The inscribed surface-relief zone plates are observed by atomic force microscope (AFM). The formation process of the surface grating and the mass diffusion in azo polymer are analyzed.
波带片 偶氮 激光诱导 表面光栅 160.5470 Polymers 310.6860 Thin films, optical properties 050.1950 Diffraction gratings Focusing properties of Gaussian beam induced by nonspiral and spiral phase plates are investigated numerically. The nonspiral phase plate introduces phase singularity to the incident beam, and the spiral one adjusts the radial phase distribution. Intensity distributions in geometrical focal plane show that the parameters of phase plates can alter the intensity distributions considerably. And local dark focal spots may be obtained, the focal spot may evolve into a circle, a two-peak spot, or a curve line, which indicates that the combination of nonspiral and spiral phase plates can be used to form novel focal spots.
相位片 焦点移动 焦点破裂 光陷阱 350.5030 Phase 230.0230 Optical devices 220.1230 Apodization The present paper proposes a novel design for achieving single-polarization single-mode (SPSM) operation at 1550 nm in photonic crystal fiber (PCF), using a rectangular-lattice PCF with two lines of three central air holes enlarged. The proposed PCF composed entirely of silica material is modeled by a full-vector finite element method with anisotropic perfectly matched layers. Simulations show that single-polarization operation within broad wavelength range can be easily realized with the proposed structure. The wide-band SPSM operation features, the low confinement losses, and the small effective mode area are the main advantages of the proposed PCF structure. A SPSM-PCF with confinement loss less than 0.1 dB/km within wavelength range from 1370 to 1610 nm and effective mode area about 4.7 micron2 at 1550 nm is numerically demonstrated.
光子晶体光纤 有限元方法 单偏振 限制损耗 060.2280 Fiber design and fabrication 060.2310 Fiber optics 060.2420 Fibers, polarization-maintaining 060.2430 Fibers, single-mode Demonstration of a 16*10-Gb/s OTDM systemDownload:571次
A 16*10-Gb/s optical time-division-multiplexing (OTDM) system was demonstrated experimentally with a well-designed ultrashort pulse source based on an electro-absorption modulator (EAM) and nonlinear fiber compressor. The obtained 10-GHz stable and pedestal-free pulse train has 2-ps width, high extinction ratio, and low timing jitter. An ultrafast demultiplexer based on a nonlinear optical loop mirror (NOLM) including a commercially available highly nonlinear fiber (HNLF) is employed to demultiplex data signal from 160 to 10 Gb/s. A back-to-back error-free demultiplexing experiment is carried out to verify the system performance.
光脉冲压缩 光脉冲产生 光时分复用 非线性光学环镜 解复用 060.2330 Fiber optics communications 320.7160 Ultrafast technology 250.0250 Optoelectronics A novel fiber-optic current sensing scheme is proposed by converting the Faraday rotation to the optical signal's degree of polarization (DOP) change. In this scheme, the lightwave passes through a fiber resonant cavity multiply and experiences Faraday rotation simultaneously. Its main merit is immunity from the environment disturbance to the fiber used in ordinary Faraday rotation sensor. Brief theoretical analysis and simulation are given to show its basic characteristics. Experimental results are demonstrated and the feasibility of the proposed method is also shown.
光纤电流传感 偏振度 光纤谐振腔 060.2370 Fiber optics sensors 230.2240 Faraday effect 260.5430 Polarization In this paper, we propose a novel method to automatically detect the belt-like object, such as highway, river, etc., in a given image based on Mumford-Shah function and the evolution of two phase curves. The method can automatically detect two curves that are the boundaries of the belt-like object. In fact, this is a partition problem and we model it as an energy minimization of a Mumford-Shah function based minimal partition problem like active contour model. With Eulerian formulation the partial differential equations (PDEs) of curve evolution are given and the two curves will stop on the desired boundary. The stop term does not depend on the gradient of the image and the initial curves can be anywhere in the image. We also give a numerical algorithm using finite differences and present various experimental results. Compared with other methods, our method can directly detect the boundaries of belt-like object as two continuous curves, even if the image is very noisy.
图像处理 带状目标分割 Mumford-Shah函数 偏微分方程 100.0100 Image processing 150.0150 Machine vision We employ the target detection to improve the performance of the feature-based fusion of infrared and visible dynamic images, which forms a novel fusion scheme. First, the target detection is used to segment the source image sequences into target and background regions. Then, the dual-tree complex wavelet transform (DT-CWT) is proposed to decompose all the source image sequences. Different fusion rules are applied respectively in target and background regions to preserve the target information as much as possible. Real world infrared and visible image sequences are used to validate the performance of the proposed novel scheme. Compared with the previous fusion approaches of image sequences, the improvements of shift invariance, temporal stability and consistency, and computation cost are all ensured.
动态图像融合 特征级融合 目标检测 双树复小波变换(DT-CWT) 100.2000 Digital image processing 100.2980 Image enhancement 100.7410 Wavelets 110.3080 Infrared imaging We propose a new subdivision technique directly subdividing the grating stripe by using complementary metal-oxide semiconductor (CMOS) microscopic imaging system combined with image processing. The corresponding optical system, subdivision principle, and image processing methods are illuminated. The relations of systemic resolution to subdivision number, grating period, magnifying power and tilt angle are theoretically discussed and experimentally checked on the Abbe comparator. The measurement precision for displacement of the proposed subdivision system is tested in the range of 5 mm and the maximum displacement error is less than 0.4 micron. The factors contributing to the systemic error are also discussed.
光栅 细分 CMOS显微成像 图像处理 测量精度 120.3930 Metrological instrumentation 050.2770 Gratings 110.2960 Image analysis A technique to calibrate faro retro probe using laser tracker system (LTS) is presented. The deep-access retro probe enables LTS to perform three-dimensional (3D) measurements of surface hidden features. It has been shown that misalignment errors are the key contributor to measuring errors of retro probe. A device for measuring misalignment errors of retro probe is invented. Theoretical analysis and experiment show that using this technique to calibrate retro probe, the misalignment errors of retro probe can be eliminated effectively and quickly.
激光跟踪系统 隐藏特征测量探头 不对称误差 校准 120.0120 Instrumentation, measurement, and metrology 140.0140 Lasers and laser optics 230.0230 Optical devices The robust phase locking of a linear diode array consisting of 49 broad-area emitters was demonstrated. The single lobe in the far field with output power of 0.83 W was observed. The far-field divergence was reduced to 2.0 mrad. The spectral bandwidth was reduced from 1.7 to 0.13 nm.
半导体激光 外腔 锁相 同相模 140.2010 Diode laser arrays 140.3290 Laser arrays 140.3300 Laser beam shaping 140.3410 Laser resonators A high efficient diode-pumped Tm:YAP laser is reported. The maximum output power at 1981 nm is 5.2 W and the slope efficiency is 30%. Unpolarized absorption near 800 nm and unpolarized fluorescence spectra near 1800 nm pumped by laser diode (LD) are measured. In addition, the relationship between operation temperature and output power is discussed.
固体激光器 激光二极管 Tm:YAP 荧光发射谱 140.3580 Lasers, solid-state 140.3480 Lasers, diode-pumped 140.3070 Infrared and far-infrared lasers A single-mode laser system with colored cross-correlated additive and multiplicative noise terms is considered. By the means of projection operator method, we study the effects of the cross-correlation time 'tau' and the cross-correlation intensity 'lambda' between noises on the normalized intensity correlation function C(s). It is found that if 'lambda'>0 ('lambda'<0), the normalized intensity correlation function C(s) increases (decreases) with increasing the cross-correlation time 'tau', and at large value of 'tau', the variation of the normalized intensity correlation function C(s) becomes small. With the increase of the net gain a0, C(s) exhibits a maximum when 'lambda' is larger. However, a minimum and a maximum appear on C(s) curves with the increase of a0 when 'lambda' becomes smaller and smaller.
单模激光 交叉关联 强度关联函数 140.3570 Lasers, single-mode 140.0140 Lasers and laser optics 140.3430 Laser theory We numerically study thermally induced birefringence and distortion in plasma electrode Pockels cell based on KD*P as the electro-optic material. This device can repetitively operate under the heat capacity mode. Simulation results indicate that the excellent switching performances and low wave-front distortion are achieved within several tens seconds working time at average power in excess of 1 kW.
热畸变 双折射 普克尔盒 等离子体电极 重复频率 高平均功率 140.0140 Lasers and laser optics 140.3540 Lasers, Q-switched 140.6810 Thermal effects The Yb:YAG and Yb:YAP crystals have been grown by Czochralski method. The absorption spectra and the fluorescence spectra of Yb:YAG and Yb:YAP crystals have been investigated. It is shown that the Yb:YAG crystal has better laser properties and smaller threshold power than Yb:YAP crystal. In addition, the absorption cross-section of the Yb:YAP crystal is 2.16 times of that of the Yb:YAG crystal, so laser diode pumped Yb:YAG lasing can be easily realized. Because YAP single crystal is anisotropic, it is provided with polarization characteristics.
材料 人工晶体 Yb:YAP晶体 光谱性能 吸收截面 发射截面 160.3380 Laser materials 160.4760 Optical properties 160.5690 Rare-earth-doped materials Base on Coulomb friction model, the workpieces with different geometry rotating in free annular polishing are simulated. From simulation, the following conclusions are drawn. The angular velocity of workpiece is higher than that of polishing pad if the ring rotates uncontrolled in free annular polishing. The circular workpiece can synchronize with polishing pad through controlling the rotation of ring, which depends on the radii of ring and workpiece, the friction coefficients of polishing pad-workpiece and ring-workpiece, and the angular velocity of polishing pad. The workpiece with sharp corner cannot contact with the ring contiguously, which causes the contact state changing and the angular velocity of workpiece fluctuating ceaselessly, and this type of workpiece should be controlled with clamp to rotate synchronistically with the polishing pad.
环形抛光 运动模拟 角速度 000.4430 Numerical approximation and analysis 220.5450 Polishing A series of Mo/Si multilayers with the same periodic length and different periodic number were prepared by magnetron sputtering, whose top layers were respectively Mo layer and Si layer. Periodic length and interface roughness of Mo/Si multilayers were determined by small angle X-ray diffraction (SAXRD). Surface roughness change curve of Mo/Si multilayer with increasing layer number was studied by atomic force microscope (AFM). Soft X-ray reflectivity of Mo/Si multilayers was measured in National Synchrotron Radiation Laboratory (NSRL). Theoretical and experimental results show that the soft X-ray reflectivity of Mo/Si multilayer is mainly determined by periodic number and interface roughness, surface roughness has little effect on reflectivity.
Mo/Si多层膜 软X射线反射率 表面粗糙度 界面粗糙度 膜层数 230.4170 Multilayers 310.1860 Deposition and fabrication 120.6660 Surface measurements, roughness 120.5700 Reflection 340.0340 X-ray optics Property of the phase of the reemitted field in the semiconductor quantum wells (QWs) excited by femtosecond pulse train is investigated. It is shown that the phase evolution of the reemitted field is controlled by the relative phase between the successive pulses of the incident train. For all the odd pulses excitation, the reemitted field is from out-of-phase to in-phase, then again to out-of-phase with the incident pulses, whereas for all the even pulses excitation, the situation is the opposite, i.e., it is from in-phase to out-of-phase, then again to in-phase with the incident pulses.
脉冲波列 量子阱 再发射场 相对相位 040.6070 Solid state detectors 140.0140 Lasers and laser optics 190.0190 Nonlinear optics 320.0320 Ultrafast optics Micro-deposition of an aluminum film of 500-nm thickness on a quartz substrate was demonstrated by laser-induced forward transfer (LIFT) using a femtosecond laser pulse. With the help of atomic force microscopy (AFM) and scanning electron microscopy (SEM), the dependence of the morphology of deposited aluminum film on the irradiated laser pulse energy was investigated. As the laser fluence was slightly above the threshold fluence, the higher pressure of plasma for the thicker film made the free surface of solid phase burst out, which resulted in that not only the solid material was sputtered but also the deposited film in the liquid state was made irregularly.
飞秒激光 激光诱导向前转移技术 薄膜 微沉积 140.7090 Ultrafast lasers 220.4000 Microstructure fabrication 160.3900 Metals 动态信息
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