【作者】 蔡国庆；

【导师】 鞠有伦；

【作者基本信息】 哈尔滨工业大学 ， 光学工程， 2014， 硕士

【摘要】 声光腔倒空是一种获得高重频窄脉宽激光输出的技术。单掺铥激光介质产生的2μm波段高重频窄脉宽激光在激光雷达、大气遥感等方面有一定应用价值。但是目前还没有单掺铥激光器方面的声光腔倒空研究，因此具有一定的研究价值。本文对单掺铥激光介质的声光腔倒空技术从理论和实验两个方面进行了研究。从理论上分析了声光调制器的工作原理，分析了衍射效率的影响因素，分析了空间声场分布。基于Tm3+的能级跃迁和速率方程，对声光腔倒空光场建立阶段进行了理论分析，分析了腔内光子数和上能级粒子数的变化趋势。基于声光调制器衍射过程，分析了声光腔倒空纳秒级脉冲的产生过程，建立了声光腔倒空光场倒空阶段理论模型。从理论上研究了脉冲宽度与声光调制器衍射效率、声光调制器内光斑大小、声光调制器内光子分布、超声场上升时间、谐振腔腔长的关系。基于速率方程研究了声光腔倒空的稳定性，分析了重复频率、泵浦速率、单程损耗、谐振腔长度对声光腔倒空稳定性的影响。首先进行了Tm:YAG晶体的声光腔倒空实验，晶体大小771.5mm3，掺杂浓度3.5%，泵浦功率19.47W时，得到了重复频率200kHz、脉冲宽度54ns、波长2013.3nm、平均功率595mW的脉冲输出。然后进行了Tm:YAG陶瓷的声光腔倒空实验，晶体大小391.5mm3，掺杂浓度4%，泵浦功率9.77W时，得到了重复频率200kHz、脉冲宽度31ns、波长2012.6nm、平均功率180mW的脉冲输出，但是脉冲波形出现畸变。最后进行了Tm:YAP晶体的声光腔倒空实验，晶体大小3316mm3，掺杂浓度3.5%，泵浦功率40.3W。当泵浦光斑大小为720μm时，脉冲波形始终存在畸变；当泵浦光斑大小为800μm时，低泵浦功率脉冲无畸变，高泵浦功率脉冲有畸变；当泵浦光斑大小为1200μm时，脉冲几乎无畸变。在1200μm泵浦光斑时，得到了重复频率200kHz、脉冲宽度50ns、激光波长1989.8nm、平均功率1.28W的脉冲输出。通过三组实验研究对比了不同重复频率条件下脉冲平均功率的变化，以及不同射频宽度条件下脉冲平均功率的变化，验证了声光腔倒空在重复频率较低时的不稳定现象。将声光腔倒空脉冲波形与主动声光调Q运转的脉冲波形作了对比，将理论计算结果和实验结果做了对比。分析了脉冲波形畸变的原因。更多还原

【Abstract】 Acousto-optical cavity dumping is a laser technology to obtain high-repetition-rate and short-pulse-width laser pulse.2μm high-repetition-rate and short-pulse-width laser obtained by Thulium single-doped laser medium can be used to lidar and atmospheric remote sensing. But there is no research on acousto-optical cavity dumping technology at thulium single-doped laser, therefore it has a certain research value. In this paper, the acousto-optical cavity dumping technology is studied in theoretical and experimental aspects.The working principle of the acousto-optic modulator (AOM) is analyzed theoretically, the factors that influence the diffraction efficiency are analyzed, and the space sound field distribution is analyzed. Based on the energy level transition and rate equation of Tm3+, the establishment stage of light field of acousto-optical cavity dumping is analyzed in theory. The changing trends of the intracavity photon number and the upper level ions number are analyzed. Based on the diffraction process of the acousto-optical modulator, the production process of the nanosecond acousto-optical cavity dumping pulse is analyzed, the theory model of dumping stage of the light field in acousto-optical cavity dumping is established. The relationship of the pulse width and the diffraction efficiency of the AOM, the laser beam size in the AOM, the distribution of photons in the AOM, the rising time of the ultrasonic wave, and the cavity length are studied theoretically.The stability of the acousto-optical cavity dumping is researched, and the effects of repetition rate, pumping rate, single loss, and cavity length on the stability of cavity dumping are analyzed.Tm: YAG crystal acousto-optical cavity dumping experiment is carried firstly, with a crystal volume of771.5mm3and a doped concentration of3.5%. When the pump power is19.47W, cavity dumping pulse with a repetition rate of200KHz, a pulse width of54ns, a wavelength of2013.3nm, and an average power of595mW is obtained. Tm: YAG ceramics acousto-optical cavity dumping experiment is carried secondly, with a crystal volume of391.5mm3and a doped concentration of4%. When the pump power is9.77W, cavity dumping pulse with a repetition rate of200KHz, a pulse width of31ns, a wavelength of2012.6nm, and an average power of180mW is obtained. But the pulse shape is aberrant.Finally Tm: YAG crystal acousto-optical cavity dumping experiment is carried, with a crystal volume of3316mm3and a doped concentration of3.5%. The maximum pump power is40W. When the pump beam diameter is720μm, the pulse shape distortion always exists. When the pump beam diameter is800μm, there is not distortion if the pump power is low, and conversely at high pump power. When the pump beam diameter is1200μm, there is almost not distortion. Cavity dumping pulse with a repetition rate of200KHz, a pulse width of50ns, a wavelength of1989.8nm, and an average power of1.28W is obtained when the pump beam diameter is1200μm.By three groups of experimental study, the difference of the average power under different repetition rates are compared, the differences of the average power under different width of the radio frequency pulse are compared, and the unstable phenomena of the acousto-optical cavity dumping are observed. These pulses are compared to the pulses of the active acousto-optical Q switching laser. The theoretical calculation results and the experimental results are compared as discussion. The reason of aberrant pulse is analyzed.更多还原