并联驱动声光调制器在连续波线性调频激光雷达系统中的应用

讨论了连续波线性调频激光雷达系统中声光调制器的设计方法，并给出了具体设计参数。提出应用两个并联驱动且声声沿相反方向传播的声光调制器来补偿由于超声波频率的改变而引起的衍射光方向的偏转，并同时提高了扫频带宽。该器件应用于线性调频激光测距实验中，取得了可信的实验结果。     

780nm声光调制器的温度特性

对780nm声光调制器(AOM)的温度响应进行了详细的理论计算,发现AOM衍射光偏振角的温度响应系数远大于衍射效率和衍射角的温度响应系数。针对AOM衍射光偏振角的温度响应,在地面实验室环境下对其进行了实验验证。在空间微重力环境下,AOM的温度响应可能会成为制约空间项目光学平台工作温度范围和性能指标提高的主要因素之一。基于AOM在实际空间应用中的脉冲工作模式,通过仿真建模给出了AOM声光晶体温度随环境温度的变化曲线,并给出了优化措施。     

外差干涉仪中声光调制器特性对测量精度的影响

提出并论证了混合型声光调制器衍射光的衍射级次混叠特性, 它使衍射光强中存在着驱动频率的谐波项, 此外入射光束的漂移将引起衍射光的频率漂移。分析了在外差干涉仪中应用它们对测量精度的影响, 提出了消除这些因素影响的方法： 利用双声光调制器外差干涉, 并在干涉仪的内部提取测量的参考信号。用双声光调制器的外差干涉仪可以实现纳米测量。     

相位、振幅调制两用声光调制器设计

针对实际应用中大多的光调制器只能实现单参数调制的情况,提出一种既可以调相又可以调幅的声光调制器的设计方案.运用矩阵级数解法求解正常声光相互作用Raman-Nath方程,通过计算机编程进行数值求解,得到衍射光的衍射光强和附加位相变化,从而指出以往解法的一些不合理性,并找到声波功率和衍射光的光强和位相的关系,为声光效应的位相调制和振幅调制设计提供了一种可行的方法.结合调制声波频率,可在同一个调制器上进行调幅、调相、调偏转方向.     

外并干涉仪中声光调制器特性对测量精度的影响

提出并论证了混合型声光调制器衍射光的笛射级次混叠特性,它使衍射光强中存在着驱动射频率的谐波项,此外入射光束的漂移将引起衍射光的频率漂移。分析了在外差干涉仪中应用它们对精度的影响,提出了消除这些因素影响的方法;利用双声光调制器外差干涉,并在干涉仪的内部提取测量的参考信号。用双声光调制器的外差干涉仪可以纳米测量。     

用超声衍射效应实现位移测量

本文叙述了用声光调制器实现位移测量的原理。入射光束与声光调制器间的相对运动引起的多普勒频移被反映光衍射的频移中去，通过测量该多普勒频移，测量出声光调制器的位移的大小，文中给出了实验结果。     

光测弹性调制器

Roditi International的PEM-90型光测弹性调制器可用于偏振测定、椭圆对称、反射差光谱学以及其它实验室。用PEM-90能测圆二向色性、线性二向色性、双折射,以及通过改变光在固定顿率(20—100kHz)上的偏振态的旋光度。     

偏振元件透振方向的判定与“穿墙而过”小魔术

介绍了利用自然光反射光即可判定偏振元件透振方向的方法,并在此基础上制作了关于光的偏振的"穿墙而过"小魔术道具.道具制作方法简单,演示效果较好,能够引起学生的好奇心,有利于帮助学生更好的理解光的偏振现象.     

双轴晶体锥光效应光盘径向寻迹研究

根据晶体锥光效应提出一种光控制方法.在双轴晶体中光波沿光轴方向入射时,其传播方向随光偏振方向的不同而改变,通过控制磁光偏振调制器上磁场强度改变光的偏振方向,从而实现对激光束方向的控制.据此分析了双轴晶体锥光效应光盘寻迹的基本原理并设计出总体方案,数值模拟计算得到晶体入射光偏振角度与寻迹位移的关系,初步验证了此方案的合理性,该方案与传统机电跟踪寻迹方式相比具有结构轻巧,动态响应快等优点.同时,也为光开关、扫描等技术提供了一种新的思想和方法.     

双轴晶体锥光效应光盘径向寻迹研究

根据晶体锥光效应提出一种光控制方法.在双轴晶体中光波沿光轴方向入射时,其传播方向随光偏振方向的不同而改变,通过控制磁光偏振调制器上磁场强度改变光的偏振方向,从而实现对激光束方向的控制.据此分析了双轴晶体锥光效应光盘寻迹的基本原理并设计出总体方案,数值模拟计算得到晶体入射光偏振角度与寻迹位移的关系,初步验证了此方案的合理性,该方案与传统机电跟踪寻迹方式相比具有结构轻巧,动态响应快等优点.同时,也为光开关、扫描等技术提供了一种新的思想和方法.     

Acousto-optic modulator of depolarized laser radiation on the paratellurite crystal

An original acousto-optic modulator of depolarized laser radiation is based on a paratellurite crystal in the regime of anisotropic diffraction by a slow acoustic wave. Two acoustic waves with different frequencies are simultaneously excited in a single acousto-optic cell. Two diffraction orders of orthogonal polarizations at the exit from the cell are diffracted in opposite sides relative to the zero order. A polarization prism that is placed immediately behind the cell transforms the diffraction orders into a single output depolarized beam. The total efficiency is 96%.     

Control of light polarization by acousto-optic diffraction from leaky acoustic wave in LiNbO₃

The acousto-optic control of light polarization due to diffraction by leaky acoustic waves in ZX-LiNbO? has been demonstrated. The randomly polarized light of 633 nm wavelength is converted by the anisotropic diffraction into two beams with mutually orthogonal polarizations, the relative intensities of which depend on the light incidence angle and acoustic frequency. Variation in acoustic frequency from 108 to 112 MHz rotates the polarization of the output optical beam by 90°. The acousto-optic control is accomplished entirely by electronic means and can be applied for implementation of fast polarization converters.     

Ultrasonic diffraction of Bessel light beams in uniaxial gyrotropic crystals

Specific features of the acousto-optic diffraction of Bessel light beams propagating in the vicinity of the optical axis of a uniaxial gyrotropic crystal have been investigated. The dependences of the diffraction efficiency on the acousto-optic interaction length, ultrasound power, and polarization state of the incident Bessel light beam have been analyzed using the coupled-wave equations and the overlap-integral method. It is shown that polarization-independent diffraction of Bessel light beams is observed in paratellurite crystals, when the Bragg diffraction efficiency is independent of the polarization state of the incident beam. The physical reason for this diffraction has been established (both theoretically and experimentally) to be simultaneous implementation of two processes of anisotropic scattering, at which the Bragg synchronism conditions are satisfied for orthogonal polarized Bessel beams with elliptical polarization.     

Optimal conditions of the acousto-optic interaction in crystals with gyrotropy

The conditions of the acousto-optic interaction in the crystals with gyrotropy are considered. The optimal length of the acousto-optic interaction and the diffraction efficiency in the gyrotropic direction are calculated. The diffraction efficiency is determined by the coupled wave method which allows calculation of the field interaction in the gyrotropic crystal [1]. It is theoretically shown and experimentally confirmed that the diffraction efficiency in the gyrotropic direction is independent of incident light polarization, when the polarization plane rotates by 45° along the interaction length.     

基于布拉格声光衍射场的光强非均匀空间分布研究

为了保证合成孔径激光雷达测试中信号光的光束质量,从波动方程出发,推导出传统的衍射光源布拉格声光作用的耦合波方程。根据测试对光束质量的不同要求,借助有限差分方法分析衍射场光强的空间三维分布,发现声场振幅的不均匀分布会影响声光衍射场的光强分布,光强分布不均造成实验中信息光源的探测难度。通过光强空间分布研究增大有效通光孔径到3 mm,解决了声光调制器光束衍射质量问题,改进后的光束质量达到实验要求。该研究方法适用于改进声光器件工作参数。     

Acousto-optic polarizer

In the paper theoretical bases are presented, as well as their experimental verification, concerning an idea of a new type acousto-optic light ellipticity modulator, based on light diffraction phenomenon by ultrasonic waves, within the so-called intermediate diffraction regime. The experimental data obtained really good match relevant theoretical predictions, and the device examined enables a continuous light ellipticity variation from 0 up to 1, with low diffraction loses and for low electric voltage applied to ultrasonic transducer.     

二维多通道声光相互作用的理论与实验研究

研究二维多通道并行超声波与光波相互作用的机理,导并求解了二维多通道声光相互作用的耦合波方程.分析了二维多通道声光相互作用中各通道的主衍射和二维多通道声光互调制的线性和非线性效应.研制了二维多通道声光器件,测试了器件的各种特性,实验结果与理论分析相符.并且用二维多通道布拉格声光调制器实现了光学矩阵-矢量运算.     

Mode locking of argon ion laser by use of cylindrical ultrasonic waves

The phenomenon of light diffraction by a cylindrical ultrasonic wave has been investigated. The diffraction was applied in a new type of acousto-optic modulator used for laser mode locking. The paper describes the modulator and presents results on mode locking of argon ion laser. The mode locking was obtained by means of a cylindrical acoustic wave launched in water at the frequencies of ultrasound 33-34 MHz. A standing wave regime of operation of the modulator resulted in a reliable generation of laser pulses with the duration 720 ps.     

Dual-frequency optical pumping for spin-polarizing a lithium atomic beam

A lithium-6 atomic beam is spin-polarized by means of optical pumping with a single-mode dye laser operating on the resonance transition. Simultaneous pumping of both hyperfine substates is achieved by frequency-splitting the laser light with an acousto-optic modulator. A polarization dependent signal, obtained by probing the optical activity of the beam with linearly polarized light, is utilized in a microprocessor-controlled laser stabilization scheme. The polarization is analyzed with a sextupole magnet and its overall value is 0.70 for an intensity of 1×10¹⁴ atms s⁻¹. By reversing the sense of circular polarization of the pumping light the atomic beam polarization is easily reversed in direction.     

二维R—N型声光光学双稳态

本文在理论上给出了对二维R-N(喇曼-奈斯)型声光作用的光学双稳系统普遍适用的动态方程,并由此导出了该声光光学双稳系统的稳态解,借助于计算机给出了取(1,0)级作为反馈级次情况下的几个级次输入～输出关系曲线,并对此进行了稳定性分析;在实验上对该理论进行了验证,实验结果与理论相符.