Generation and Modulation of Phase Difference of Output Intensities in a Feedback Nd:YAG Laser with an Extracavity Waveplate Rotated

External anisotropic feedback effects on the phase difference behaviour of output intensities in a microchip Nd：YAG laser are presented. By rotating a quarter wave plate placed in the external cavity, the angle between laser initial polarization direction and o-axis of the wave plate is tuned from -45°to 45°, which results in variable extra-cavity birefringence along two orthogonal detection directions. With only one optical path and one wave plate, laser intensities of the two orthogonal directions, both modulated by the external cavity length, are output with a tunable phase difference, which can be continuously changed from zero to twice as large as that of the waveplate. Experimental results as well as a theoretical analysis based on Fabry-Perot cavity equivalent model and the refractive index ellipsoid, are presented. The potential applications of this phenomenon are also discussed.     

Distortion of optical feedback signals in microchip Nd:YAG lasers subjected to external multi-beam interference feedback

This paper proposes a theoretical analysis for the characteristics of an external cavity Nd:YAG laser with feedback of multiple-beam interference, which is induced by the multi-reentrance of the light from the external Fabry--Perot cavity. The theoretical model considers the multiple beam interference of the external Fabry--Perot cavity. It is found that the optical feedback signals are distorted to pulse waveforms instead of the sinusoidal ones in conventional feedback. The experimental results are in good agreement with the theoretical analysis. The obtained theoretical and experimental results can advance the development of a laser feedback interferometer.     

External-cavity birefringence feedback effects of microchip Nd:YAG laser and its application in angle measurement

External-cavity birefringence feedback effects of the microchip Nd:YAG laser are presented. When a birefringence element is placed in the external feedback cavity of the laser, two orthogonally polarized laser beams with a phase difference are output. The phase difference is twice as large as the phase retardation in the external cavity along the two orthogonal directions. The variable extra-cavity birefringence, caused by rotation of the external-cavity birefringence element, results in tunable phase difference between the two orthogonally polarized beams. This means that the roll angle information has been translated to phase difference of two output laser beams. A theoretical analysis based on the Fabry--Perot cavity equivalent model and refractive index ellipsoid is presented, which is in good agreement with the experimental results. This phenomenon has potential applications for roll angle measurement.     

基于猫眼腔镜损耗调节的激光横模演示系统

提出一种基于猫眼腔镜损耗调节的新型激光横模演示系统。采用半外腔He-Ne激光器,利用由分立的可进行五维微调的凸透镜和凹面镜组成的猫眼逆向器构成损耗可调激光谐振腔,通过调节猫眼逆向器改变激光谐振腔的损耗比，实现改变激光横模状态的作用。利用CCD进行图像采集，计算机实现图像存储，从而得到20多种结构清晰的高阶横模花样图片。     

表面炭化磺酸基型阳离子树脂的制备及其对Fe(Ⅲ)吸附性能的研究

将对苯乙烯磺酸钠(SSS)聚合接枝到表面炭化的CD301树脂表面,成功制备出一种新型吸附材料PSSS-g-CD301。研究了影响表面引发接枝聚合的主要因素,并采用静态法考察了PSSS-g-CD301对Fe(III)的吸附行为。结果表明,在接枝过程中,适宜的接枝时间是10h,适宜的引发剂用量为单体质量的1%,适宜的温度为35℃,适宜的单体质量分数为10%。PSSS-g-CD301对Fe(III)的吸附容量可以达到0.28mmol/g(p H=2,温度288K);准二级动力学方程可以更好地描述吸附动力学规律;吸附行为符合Langmuir与Freundlich吸附模型;热力学参数?H、?G、?S的计算结果表明,该吸附过程为自发的放热过程。     

半外腔微片Nd∶YAG正交偏振激光器及其在精密测角中的应用

设计了一种半外腔微片Nd∶YAG正交偏振双频激光器。把2个1/4波片置于激光谐振腔内,一个静止,一个作360°旋转,旋转引起2个1/4波片快轴之间的角度变化被激光器转化成激光2个频率之差的变化,从而输出可调谐的双频激光。采用琼斯矩阵对光在腔内的本征模进行分析,给出了双频频差的理论解释。讨论了一种体积小、分辨率高和可整周测量的新型Nd∶YAG激光测角仪的潜在前景。     

基于双机直流拖动的自动开关系统设计

接触器控制的建筑天窗自动开关系统已经不符合现代建筑需求,并会加大日常维护工作。本文采用了双机直流拖动的自动控制系统,通过模型的建立和控制原理的分析,对系统的软件和硬件进行了设计。     

布里渊散射分布式光纤传感器研究热点跟踪

综述了基于布里渊散射的分布式光纤传感技术最新进展。介绍了其测量原理和研究现状;阐述了该领域目前的热点研究问题,包括空间分辨率提高、解决多参量测量的交叉敏感问题、消偏振衰落提高测量精度等;比较了各种解决方案的利弊;展望了今后的发展方向。     

Polarization switching in a quasi-isotropic microchip Nd:YAG laser induced by optical feedback

This paper demonstrates the influence of external optical feedback on the polarization state of longitudinal modes in quasi-isotropic microchip Nd:YAG lasers. Under optical feedback, the polarization state of longitudinal modes in quasi-isotropic lasers relies strongly on the intracavity anisotropy loss and mode competition. When the intracavity anisotropy loss is small, external optical feedback can cause polarization switching and strong mode competition between two orthogonal linearly polarized eigenstates of one laser longitudinal mode, which leads to the distortion of laser intensity modulation waveform. The polarization switching is independent of the initial external cavity length. By increasing the intracavity anisotropy loss, one polarization eigenstate can be suppressed and the laser works in single-polarization state. A theoretical analysis based on the compound cavity model is presented, which is in good agreement with the experimental results. The results offer guidance to the development of laser feedback interferometers.     

各向异性外腔微片Nd:YAG激光器调频回馈研究

研究了在各向异性外腔下微片Nd:YAG激光器调频回馈特性.作为对比,首先给出了在各向同性外腔下调频回馈结果,激光器输出功率的半波条纹数正比于外、内腔长度之比.在回馈外腔中内置一个四分之一波片,激光偏振态发生规律性跳变,每个纵模带宽内的偏振跳变次数正比于外、内腔长之比,相同外腔长下,回馈条纹再次倍频.进行了基于法布里-珀罗腔等效模型的理论分析,结果和实验相符合.此现象在精密测量领域有潜在应用. 关键词： 光回馈 调频回馈 各向异性外腔 半波条纹数