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在CO2激光泵浦的气体太赫兹源中,泵浦激光的频率稳定性控制问题十分关键。针对基于光声效应的泵浦源稳频技术,理论分析和数值模拟了光声信号的探测条件(光声腔内气压、传声器灵敏度等)对微弱光声信号检测的影响,进而对探测条件进行了优化。在此基础上,进一步分析了泵浦激光频率在气体吸收谱线中心频率附近漂移时光声信号的变化规律。结果表明:在实际工作中,为了实现高精度的稳频,需要将光声腔的气压控制在低压范围内,并采用高灵敏度的光声传感器;当泵浦激光频率产生漂移时,利用探测到的微弱光声信号通过反馈系统可以精确地改变激光器的腔长,以实现高精度的光声稳频,且频率漂移范围可控制在MHz量级以内。
In the CO2 laser pumped gas terahertz source, the problem of frequency stability control of the pump laser is critical. Aiming at the PSF technique based on the photoacoustic effect, the influence of the detection conditions of the photoacoustic signal (the pressure of the photoacoustic cavity, the sensitivity of the microphone, etc.) on the detection of the weak photoacoustic signal is theoretically analyzed and numerically simulated, and the detection conditions are further studied optimization. On this basis, the variation law of the photoacoustic signal when the pump laser frequency drifts near the center frequency of the gas absorption line is further analyzed. The results show that in the practical work, in order to realize high-precision frequency stabilization, it is necessary to control the pressure of the photoacoustic cavity in the low pressure range and adopt the high-sensitivity photoacoustic sensor. When the pump laser frequency is drifted, the detected Faint photoacoustic signals The cavity length of the laser can be precisely changed by the feedback system to achieve high-precision photoacoustic stabilization with frequency drift within the order of MHz.