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用于CO2激光外差探测的声光移频器研究
【作者】 邓明；
【作者基本信息】 电子科技大学 ， 光学工程， 2008， 硕士
【摘要】 本文从分析声光互作用基本原理出发,利用多重平面波散射理论,建立声光移频器的数学模型,进行声光移频器的参数设计分析;通过对体波高频远红外声光移频器进行系统的研究,特别是针对远红外声光器件在高功率激光中的应用特点,采取了背面吸热结构和环绕式水冷却结构等控制器件温升措施,及时降温散热,保持器件内温度均匀恒稳,消除器件内部温度梯度,使衍射效率提高10%,光斑质量也明显改善。本文详细介绍了以锗单晶(Ge)声光互作用材料、铌酸锂(LiNbO3)换能器及冷铟真空压焊工艺为主的声光移频器完整的设计流程和制作程序。在深入分析锗(单晶)材料的改性机理的基础上,通过对精选优质的单晶锗、镀制电极、焊接电极线等材料和工艺问题的创新性和探索性研究,研制出了高衍射效率、高可靠性的中远红外声光器件。本文还详细介绍了声光移频器匹配电路网络的设计方法,设计出了中远红外声光移频器的换能器与声光互作用材料最佳匹配网络。本文给出了实验测试器件的衍射效率、消光比、光学透过率等指标以及器件移频与超声波频率的相关性验证的实验方案。当输入电功率超过15W,驱动频率不变时,声光移频器件内温度明显上升,恒温效果差,光斑质量变差,衍射效率开始下降。最后分析了远红外声光移频器在激光外差相干探测、相干探测型激光雷达、粒子碰撞速度分析仪中的应用前景。
【Abstract】 Based on the acousto-optic interaction principle and multiple plane-wave scattering theory, the mathematical model of acousto-optic frequency shifter (AOFS) is built to determine its parameters. Through systematically studying on the bulk-wave high-frequency far-infrared acousto-optic frequency shifter (AOFS), especially on the application characteristics of high-frequency far-infrared acousto-optic devices in high power laser, some temperature-controlled methods, such as back endothermic structures and surround-based water cooling structures, are used to remove heat instantly to keep the internal temperature of acousto-optic devices uniform and eliminate the temperature gradient. With these methods, the diffractive efficiency can be increased 10% and the spot quality is improved greatly.This dissertation introduces the whole design and fabrication procedure of the acousto-optic frequency shifter and presents detail descriptions on the mono-crystal germanium acousto-optic interaction materials, LiNbO3 transducer, and cold-indium vacuum pressure welding process. Based on analyzing modification mechanism of mono-crystal germanium, innovation study on the materials or processes about the fine selection of mono-crystal germanium, electroplating electrode and welding electrode wire is carried out and the middle and far-IR acousto-optic devices with high diffractive efficiency and high reliability is developed successfully.The design method of the matching-circuit network for acousto-optic frequency shifter is also described in detail and the optimal matching network between transducer and acousto-optic interaction material of middle far-IR AOFS is obtained.In this dissertation, the experimental parameters (such as diffractive efficiency, extinction-ratio, optical transmittance, etc) for test devices are determined and test scheme for the correlation of the AOFS frequency shift and ultrasonic frequency is presented. When the input power is over 15W and the driving frequency is stable, the internal temperature of the AOFS rises obviously, and as a result the thermostatically controlled condition the spot quality is poor and the diffractive efficiency begin to deteriorate.The potential application of AOFS in laser heterodyne coherent detection, coherent-detection-based laser radar, particle collision velocity analyzer is discussed briefly.