Polarization-phase dynamics in a four-frequency gas ring laser with elliptical polarization of counter-propagating waves

Based on a developed and experimentally tested model, self-oscillatory lasing regimes have been studied for a Class A four-frequency gas ring laser with linear coupling of elliptically polarized counter-propagating waves. In the self-oscillatory regime, switching of the intensities, polarization states, and phase differences of the counter-propagating waves is observed, and also a polarization-phase dynamics effect involving displacement of the intensity switching point (with respect to detuning), due to the phase shift as a result of an ellipticity different from zero. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 5, pp. 620–625, September–October, 2006.     

Azimuthal dependence of the two-photon absorption coefficient for CdP2 crystals with tetragonal syngony

We studied the two-photon absorption coefficient (β) for cadmium diphosphide (CdP₂) single crystals in the tetragonal modification vs. the polarization azimuth (φ) of the incident light for intensities close to the optical breakdown (or optical damage) threshold for the crystal (11 MW/cm²). We have established that the value of β_max = 0.16 cm/MW is reached for φ = 0, i.e., for the ordinary wave. At the lasing frequency of a ruby laser, β_⊥/β_|| = 2.13, which suggests anisotropy of the two-photon absorption in the studied crystals. These dependences are needed for design and fabrication of quantum electronics and nonlinear optics elements whose operation is based on the use of the two-photon absorption effect for high radiation fluxes. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 76, No. 1, pp. 117–121, January–February, 2009.     

布儒斯特角切割LiNbO3晶体的偏振态分析

基于琼斯矩阵和菲涅耳公式,建立了偏振光透过LiNbO3晶体的分析模型,研究了入射光偏振态、晶压等参数对输出光偏振态和p偏振态、s偏振态透射率的影响规律。搭建了分别含单块LiNbO3晶体、LiNbO3晶体和薄片、两块串联LiNbO3晶体的Ho,Tm,Cr:YAG激光电光调Q实验装置,并测得了输出激光的偏振态、输出能量等随晶压的变化关系曲线。     

Diagnostic system for two dimension intensity distribution of laser beam

The diagnostic system for two dimension(2-D)intensity distribution of laserbeam is a measuring instrument for many parameters of laser beam.2-D intensity distributionplot of laser beam is obtained by the two dimension scanning mirror which is controlled by amicrocomputer to scan the laser beam on a detector.Many parameters of laser beam such asthe isointensity distribution plot,the beam diameter,the beam waist diameter,the laser pow-er,the diverge angle and the beam brightness,are given by means of the microcomputer pro-cessing the data measured.Theoretical analysis of beam parameter transform is given.     

铷原子蒸汽中的光偏振旋转效应

对铷原子(⁸⁷Rb)蒸汽中的法拉第旋转、光学偏振自旋转以及二者的叠加旋转效应进行了理论和实验研究.对三种情况下旋转现象建立了简单而有效的理论模型. 实验中把铷原子泡置于自行设计的磁屏蔽腔内, 以屏蔽地磁场的影响.实验选择⁸⁷Rb F=2→F'=3能级D2跃迁线并采用零多普勒光谱 实验结构消除多普勒展宽对实验光谱的影响. 实验中分别观测到了三种旋转现象,实验结果与理论模拟结果非常符合.     

Tight focus of a radially polarized and amplitude- modulated annular multi-Gaussian beam

The focusing of a radially polarized beam without annular apodization ora phase filter at the entrance pupil of the objective results in a wide focus and low purity of the longitudinally polarized component. However, the presence of a physical annular apodization or phase filter makes some applications more difficult or even impossible. We propose a radially polarized and amplitude-modulated annular multi-Gaussian beam mode. Numerical simulation shows that it can be focused into a sharper focal spot of 0.125λ² without additional apodizations or filters. The beam quality describing the purity of longitudinally polarized component is up to 86%.     

冰洲石-玻璃组合e光超高透偏光棱镜

为了既节省稀有昂贵的冰洲石晶体材料，又尽量提高偏光棱镜的透射比，设计了一种冰洲石晶体与光学玻璃组合的方法。叙述以布儒斯特角入射来提高偏光棱镜e光透射比的设计方案。该棱镜可用甘油或有机硅胶将FK 2玻璃与冰洲石晶体胶合而成。理论分析和实验测试表明，该棱镜的透射比高于96％，消光比优于10-5，在一定情况下可以取代纯冰洲石晶体材料的偏光棱镜。     

用拉盖尔-高斯激光对真空中电子直接加速

对用拉盖尔-高斯(LG)光束加速电子作了研究.结果表明，仅模指数为p和l=1的LG光束的纵向电场可用于加速电子.模指数为p和l=1的线偏振和圆偏振LG光束都对电子有加速效果.对轴上光场的相速度和群速度以及电子能量增益等物理特征作了讨论.给出了轴上光场的相速度和群速度、加速电位及电子能量增益等的解析表达式，并作了数值计算和分析. 关键词： 激光电子加速 拉盖尔-高斯光束 线偏振和圆偏振 能量增益     

Design of a compact polarization beam splitter based on a deformed photonic crystal directional coupler

In this paper a compact polarization beam splitter based on a deformed photonic crystal directional coupler is designed and simulated. The transverse-electric （TE） guided mode and transverse-magnetic （TM） guided mode are split due to different guiding mechanisms. The effect of the shape deformation of the air holes on the coupler is studied. It discovered that the coupling strength of the coupled waveguldes is strongly enhanced by introducing elliptical airholes, which reduce the device length to less than 18.Sttm. A finite-difference tlme-domain simulation is performed to evaluate the performance of the device, and the extinction ratios for both TE and TM polarized light are higher than 20 dB.     

Periodic intensity variations on the pulse-train of a passively mode-locked fiber ring laser

We investigate the evolvement of the periodic intensity variations of the pulse-train in a fiber ring laser mode-locked by the nonlinear polarization rotation technique. It is found that the phenomenon of such intensity fluctuations is related to the orientation of the polarization controllers when the pump power is fixed. The numerical results show that the mechanism of the periodic intensity variations is caused by the interaction of the nonlinear polarization rotation and the passive polarizer in the cavity.     

会聚线偏振强激光场中氢原子的能态变化

本文研究氢原子在会聚的线偏振强激光场中原子势的变化以及由此而引起的原子能级移位和波函数的空间扩展问题.结果表明,变化后的原子势等价于半径由外场决定而荷电量为核电荷的振荡球壳的势.在此势下,原子能级将变浅和分裂,波函数的空间分布将增大.     

双折射双频激光器偏振特性的分析

用激光原理和晶体光学原理分析了腔内加旋光晶体的激光器输出光的偏振特性，实验和分析表明，激光器输出两束不同频率的垂直线偏振光，激光器两端输出光的偏振面有一夹角ａ，且此夹角与晶轴和传光方向的夹角θ有关。理论计算结果在双折射双频激光器的实验结果符合很好。     

Transformation of an elliptic into a circular beam using a diffractive binary optic

We propose a new method for transforming an elliptic Gaussian beam, in the near field, into a circular Gaussian beam in the far field. For that, we consider the use of a simple binary diffractive optic which is able to circularize an elliptic beam of 2:1 aspect ratio.     

一种教学用简易飞秒光纤激光器的研制

介绍了一种适合于日常高校光学或光电技术专业的研究生和高年级本科生熟悉、了解飞秒激光教学实验用的飞秒光纤激光器.该飞秒激光光源基于非线性旋转偏振效应被动锁模原理,输出脉冲宽度为440 fs、脉宽带宽积为0.362、中心波长在1560 nm附近、平均输出功率为12mW、脉冲重复频率为31.15MHz.     

Intracavity-frequency-doubling of a 946 nm Nd:YAG laser with cadmium mercury thiocyanate crystal

We report the intracavity-frequency-doubling of a 946 nm Nd:YAG laser with a CMTC crystal at room temperature. A cw output power of 1.64 mW of blue light at 473 nm is obtained. To our knowledge, this is the first time that CMTC crystal has been used to frequency double a 946 nm Nd:YAG laser.     

基于椭圆偏振光注入垂直腔表面发射激光器的正交偏振模式单周期振荡产生两路光子微波

提出了基于椭圆偏振光注入下垂直腔表面发射激光器(VCSEL)输出的正交偏振模式单周期(P1)振荡来同时获取两路光子微波的实现方案, 并进行了相关仿真研究. 结果表明: 在合适的参数条件下, 一个自由运行的VCSEL(定义为主VCSEL, M-VCSEL)可输出椭圆偏振光, 其X偏振分量和Y 偏振分量具有相同的激射频率; 将M-VCSEL输出的椭圆偏振光注入到另外一个VCSEL(定义为副VCSEL, S-VCSEL), 在给定主副VCSEL间频率失谐的条件下, 通过选择合适的注入强度可使S-VCSEL 中两个偏振分量均呈现单周期(P1)振荡, 从而可获得两正交的光子微波信号; 随着注入强度的增加, 光子微波的频率以及功率均呈现增加的趋势; 结合微波频率、功率以及输出光谱中第一边带和第二边带的幅度差在由注入强度和频率失谐所构成参数空间下的分布图, 可确定获取高品质微波信号的优化注入参数范围.     

Orthogonal-polarization compensation method for measuring unsteady vertical force of a bumblebee in a wind tunnel

It is important to measure the unsteady vertical force of an insect in a wind tunnel for studying the flight performance of insects. Optical method can measure it with high accuracy, but it is affected by air turbulence. An orthogonal-polarization compensation (OPC) method is developed for measuring the beating force of a bumblebee in a wind tunnel and compensating the error due to beam fluctuations induced by air turbulence. The applicability of the OPC method was confirmed by using a piezo translator to generate the tilt angle variation. The results show that by using the OPC method, the error in tilt angle measurement due to air turbulence can be decreased by about 80% compared with that using the conventional angle measurement method. The OPC method was then applied to measure the tilt angle variation caused by the beating motion of a bumblebee attached to one end of a sensor block in a wind tunnel for a wind velocity of 1.1 ms⁻¹. The results confirmed the effectiveness of this new method.     

大气湍流中部分相干光束上行和下行传输偏振特性的比较

以部分相干的电磁高斯-谢尔模型(electromagnetic Gaussian-Schell model, EGSM) 光束为研究对象, 根据相干和偏振的统一理论以及随机光束的Stokes参量, 推导出EGSM光束在大气湍流中斜程传输时的偏振度(degree of polarization, DoP)和偏振方向角的表达式, 研究了大气湍流中上行和下行传输时EGSM光束偏振特性的不同. 研究结果表明: 在相同条件下, EGSM 光束下行传输时整个光场DoP的分布比上行传输要集中; 下行传输时轴上点的DoP达到最大值所对应的传输距离长于上行传输. 可以看出, EGSM光束沿下行路径传输时, 探测器可以接收更远距离处的波束传输信息.     

大型精密光学调节架的俯仰角运动控制方法及误差修正

航天遥感仪器的光学装调需要使用大型精密调节架,其俯仰角调节机构使用步进电机驱动,且传动比为非线性,因此控制难点在于如何以步进电机开环方式来实现调节架俯仰角的精确运动。通过对现有调节架的俯仰角运动机构进行建模分析,得到其运动学模型为偏心曲柄滑块机构。根据运动学公式,分析了当前使用的控制方法精度不高的原因,并提出了新的控制方法。在此基础上,为了验证新方法下调节架俯仰角的运行结果,引进了全新的测量工具一激光跟踪仪。根据测量结果,绘制出俯仰角的目标值和误差曲线图,分析误差规律并修正。经复测,俯仰角的运动精度最终达到了光学装调的要求。     

Optical properties of cadmium sulfide nanocrystals obtained by the sol-gel method in gelatin

Based on analysis of optical absorption data for CdS nanocrystals obtained by sol-gel technology in gelatin, we have studied the effect of technological factors (reagent concentrations, gelatin concentration) on the growth process and size distribution of the synthesized nanocrystals. Depending on the reagent concentration, we synthesized CdS nanocrystals with mean radii in the range . We have shown that for a low gelatin content (1%), nanocrystals of different sizes are formed (1.7 nm and 2.6 nm). With an increase in the gelatin concentration, the size dispersion decreases and nanocrystals of a single mean radius (2.3 nm) are formed. We have established a correlation between the size dispersion and the shape of the photoluminescence spectrum of the CdS nanocrystals. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 4, pp. 556–562, July–August, 2008.