利用波长调制技术以及数字PI控制器将外腔二极管激光器(ECDL)稳定到1.6μm处的甲烷气体吸收线上.稳定后的激光频率波动小于5.6MHz,相对于自由运转时的160MHz有了很大提高,而误差信号的Allan方差均方根(即稳定度)在平均积分时间为64s时达到最小值1.66×10-11.从理论上定性分析了频率稳定度受到的各种限制因素,最后得出本实验中频率稳定度主要受频率调制和探测器噪声限制的结论,同时给出了提高频率稳定度的方法.被稳定的激光器主要用于为甲烷气体浓度监测提供频率参考.

The frequency of an external-cavity diode laser has been stabilized to absorption line of methane at wavelengths around 1.6 μm by employing the wavelength modulation technique and the digitized controller. The frequency fluctuation of the stabilized laser is held within 5.6 MHz and better than 160 MHz of the free-running laser. The root of Allan variance of error signals reaches a minimum of 1.66×10 -11 when averaging time is 64 s, well within the precision needed for application. And various limiting factors are analyzed. It is found that the stability is mostly limited by the noise of photodetector and frequency modulation in the experiment. Several methods of improved stability are also presented here. Such a treatment can provide a guidance of any experiment of frequency stabilization. The primary application of this stabilized laser is to provide a frequency reference for remote sensing of the concentration of methane.