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差频光源用于大气分子稳定同位素丰度研究需要频率稳定的连续输出的空闲光。基于连续可调谐钛宝石激光器和单频连续Nd:YAG激光器建立差频系统,为了稳定差频系统产生的红外光源的波长,利用MgO:PPLN作为倍频晶体,采用有多普勒展宽的碘分子吸收稳频方法,结合数字比例-积分-微分(PID)反馈控制技术,将Nd:YAG激光器的频率漂移量稳定在1.2MHz/h内,稳定度为4.26×10-9。实验结果表明:增加对压电陶瓷(PZT)的调制电压时,Nd:YAG激光在1h内的频率漂移量迅速减小,超过1V后漂移量趋于稳定;改变对PZT调制频率没有获得较高的稳定度。将频率稳定后的Nd:YAG激光用于产生3.42μm附近的差频光源,通过对低压下CH4气体分子吸收谱线的测量,去卷积运算得到差频系统的线宽约为6.9MHz。实验结果既为该方法用于稳定激光频率提供了重要的参考,又为痕量气体探测提供了频率稳定的差频光源。
Difference frequency light sources are used for atmospheric molecular stable isotope abundance studies which require continuous output of free light with frequency stability. Based on the continuous tunable Ti: sapphire laser and the single frequency continuous Nd: YAG laser, a differential frequency system was established. In order to stabilize the wavelength of the infrared light source produced by the differential frequency system, MgO: PPLN was used as a frequency doubling crystal and iodine molecules with Doppler broadening Absorption frequency stabilization method, combined with digital proportional-integral-derivative (PID) feedback control technology, the frequency drift of Nd: YAG laser is stabilized within 1.2MHz / h and the stability is 4.26 × 10-9. The experimental results show that when the modulation voltage of PZT is increased, the frequency drift of Nd: YAG laser rapidly decreases within 1h, and the drift tends to be stable when the modulation voltage of PZT is higher than 1V. Stability. The frequency stabilized Nd: YAG laser was used to generate the difference frequency light source near 3.42μm. The line width of the difference frequency system was about 6.9MHz by measuring the molecular absorption spectrum of CH4 gas under low pressure. The experimental results not only provide an important reference for stabilizing the laser frequency, but also provide a frequency-stabilized difference frequency light source for trace gas detection.