染料液晶同激光的非线性光学效应研究

本文研究了激光同染料液晶的非线性光学效应。理论分析了激光在染料液晶中的传输过程,分别计算了当入射激光功率为10mW/cm2和50mW/cm2时的输出激光光强分布。实验测量了532nm连续激光通过染料液晶传输后的光限幅曲线,观察了输出激光光斑形状随入射激光光强的变化,实验结果与计算结果基本相吻合。     

白宝石晶体的激光损伤

测量了1.06μm和0.53μm激光对温梯和提拉法生长的白宝石晶体的表面和体损伤阈值,分析了各种因素对损伤的影响,讨论了不同的损伤机理。     

激光诱导向列相液晶分子重新取向的研究

用液晶分子运动的动力学方程,求出了激光诱导向列相液晶分子重新取向的取向角、折射率改变、阈值场强和上升时间的近似表达式。讨论了它们随液晶材料参数、激光强度和激光在液晶中传播方向的变化,进行了数值计算。给出了激光能诱导向列相液晶分子重新取向的必备条件,得到向列相液晶的各向异性是其分子重新的取向的根本原因。     

用光栅作为分束器的激光光栅干涉仪

本光栅干涉仪用光栅作为分束器,使双光束发生干涉。特点是既可用来观察位相物体,也可把干涉条纹调制在位相连续变化的物体上进行测量。     

Bragg reflection from a phase grating induced by nonlinear optical effects in liquids

Bragg reflection of light from a phase grating has been used as a technique for the investigation of nonlinear optical phenomena. A continuous argon ion laser was used to probe the structure induced in a liquid by the nonlinear interaction of a high-intensity ruby-laser beam with that liquid. This arrangement had the advantage of allowing direct space and time-resolved measurements of the induced effects.     

Laser induced line narrowing and saturation broadening effects in OPFIRL

The variation of the laser linewidth within an optically pumped NH3 FIR laser has been studied theoretically on the basis of three-level quantum system approach. It has been shown that the activated medium within the sample tube of an optically pumped ASE FIR laser can be divided into three regions: A). Laser induced line narrowing region, in which the FIR laser linewidth is less than Lorentz linewidth; B). Saturation broadening region, in which the power density of the FIR. signal becomes large enough to make saturation effect important and the linewidth broadens; C), Self-absorption narrowing region, in which the pumping energy density is below the threshold, so self-absorption dominates and the linewidth decreases. The necessary linewidth of the OPFIRL can be obtained by appropriate selection of the length of the sample tube.     

Laser induced refractive index inhomogeneities and absorption saturation effects in CdS

We have studied an optically-induced index inhomoganeity in CdS. Using ∼10 mW of focused laser radiation whose frequency is near the band gap, a reduction in index as large as one part in 10³was observed which resulted in induced lenses with focal lengths as short as 1 mm. We also find large absorption saturation and highly efficient recombination radiation (green edge emission) accompanying the index effects. Changes in optical transmission of two orders of magnitude and quantum conversion efficiencies of ∼50 percent were measured. The effects occur in selected samples near liquid nitrogen and liquid hydrogen temperature. Various mechanisms for the inhomogeneities are discussed. The effect is ultimately attributed to the presence of compensated Cd acceptor vacancies which act, directly or indirectly, as absorbing centers. The relevance of these effects to laser-induced index inhomogeneities occurring in LiNbO3and LiTaO3is discussed.     

某些有机晶体的倍频效应与分子偶极矩之间的关系

初步论证了有机共轭分子的偶极矩与其倍频效应的联系,并采用EHMO法对4-硝基吡啶-1-氧的3位和2位甲基衍生物及4-硝基苯胺的2位和8位卤素衍生物的分子偶极矩进行了理论计算,合成并测定了它们的倍频性能和偶极矩.实验结果与理论预测规律相吻合.     

基于正弦透射光栅的激光告警接收机研究

在光电对抗中,高速、可靠地获取敌方来袭激光的参数是实施有效对抗的关键。提出了基于正弦振幅透射光栅衍射原理的窄脉冲激光波长和入射方向的测试方法,并设计了激光告警接收机原理样机,该样机由光栅、平凸柱面镜、ATMEL公司的驱动频率为50MHz的线阵CCD探测器、高速数字信号处理器TMS320V C5509和液晶显示电路构成。结果表明,该样机可达到如下技术指标:波长范围为500～1100nm、波长分辨率≤10nm、视场范围为22.5°、角度分辨率≤1°、反应时间<0.1s、灵敏度<10mW/cm2。     

激光振镜直写光栅误差分析及校正方法

针对振镜式激光直写光栅系统中存在的扫描畸变的问题,提出了一种内部转角优化和外部扫描误差补偿相结合的校正方法。以光栅栅距10μm为目标,建立了振镜系统的几何光学模型,对扫描误差进行了分析,然后对振镜转角进行了优化,进一步对振镜进行了曲线拟合补偿,坐标点(100,10)处误差从0936mm,1912mm降低到0148μm,00296μm。结果表明,这种方法能够满足振镜式激光直写光栅在短距离刻划的精度要求。     

液体中的激光脉冲光声效应和光偏法检测

本文论证了液体中激光脉冲光声效应和光偏法探测技术及其用来测量流体声速的可能.设计了实验光路,测量了不同温度下水中的声速.     

Elasto-optically induced modulation of in-fiber grating

Strong effects due to uniaxial stress applied to an in-fiber grating reflection peak splits because of the elastooptically induced birefringence. The separation between the two peaks increases with the stress, and they broaden and shift. By modulating the pressure using a PZT disk at frequencies up to 1 MHz, modulation of the reflectivity, which varies with the wavelength within the grating reflection band, was obtained     

光致折变晶体中相位光栅的相位移动的物理作用

在光致折变晶体(如SBN,BaTiO_3等)中发生两波混频及能量耦合是由于晶体干涉场内产生了相对于干涉场有相位移动的折射率光栅(相位光栅),这已被实验和理论证实。如果仅有两波混频产生的相位光栅,而此光栅相对于干涉场并无相位移动,或相位移动量较小(不足π/2),此时不会发生波能量耦合或耦合极微弱。1981年A.Yariv用耦合波方程从数学上解决了这个问题。     

Laser-beam modulation using grating diffraction effects

An optical-diffraction modulator, using an electro-optic crystal excited by a periodic array of metallic conductors, is described. The operation of the device is in some ways similar to that of an acoustoelectric modulator; it differs from it in that it has a bandwidth, potentially very wide, which extends from d.c. It may therefore find application as a baseband modulator.     

Laser-beam modulation using grating diffraction effects

An alternative system for producing an electro-optic grating modulator is discussed. A polarisation grating is used to overcome electric-field reduction occurring with closely spaced electro-optic grating electrodes.     

Laser beam modulation using corner reflector and deep diffraction grating

A new scheme of the power modulator of laser beam is based on a corner-reflector unit with a relief diffraction grating that is placed on a plane of the unit and has a relief depth of several wavelengths of the laser radiation. It is shown that angular oscillations of the unit make it possible to implement modulation of the zero-order diffraction beam at a modulation depth of almost 100% and a relatively high linearity of the modulation characteristic that is reached at modulation depths of greater than 50%.     

Dynamic self-diffraction effects in liquid crystals

The dynamic self-diffraction effects due to large optical nonlinearities of nematic liquid crystals via molecular reorientation are reviewed. The laser-induced gratings are shown to arise because two waves with ordinary and extraordinary polarizations propagate in a nonlinear anisotropic medium. Both threshold and thresholdless effects as well as nonlinear scattering in an initially nonhomogeneous medium are discussed. Direction of further work in this field as well as potential applications are indicated.     

Pump-induced thermal effects in Er-Yb fiber grating DBR lasers

Large absorption of 980-nm pumping in Er-Yb doped fibers causes significant temperature differentials along small length of the fibers. When pumped with 40 mW of power, unequal Bragg wavelength shifts of 0.25 and 0.16 mm were measured in the respective 6- and 10-mm-long Bragg reflectors constructed around the Er-Yb core of a 2.5-cm-long DBR laser. This causes large fluctuation in the laser's output power. Stable operation resumed with increased pump power. At 68 mW of pump power, 0.32-nm shift in lasing wavelength (corresponding to a temperature rise of 38°C) was measured in the distributed Bragg reflector fiber laser