基于声光偏频法的激光频率无调制锁定

为了进一步提高1.5 μm波段激光器的频率稳定性,利用声光调制器(AOM)的频移特性使激光发生频移,将乙炔(~(12)C_2H_2)v_1+v_3带的P9支吸收峰作为参考频率,通过两条频移的吸收谱线产生类色散鉴频曲线,实现对外腔半导体激光器的无调制频率锁定.实验中把以前直接对激光器的调制转移到声光调制器上,避免了直接调制所引入的额外噪声,通过闭环锁定,50 s内典型的频率起伏达到5.8 MHz以内,激光器的频率起伏较自由运转时明显得到抑制,实现了激光频率的稳定.

Modulation-free Frequency Locking of a Laser Based on Acousto-optic Frequency-shifting Method

In order to improve the frequency stability of laser in 1.5μm regions, two acousto-optic modulators were used to shift the laser frequency and the absorption spectra of an acetylene transition (~(12)C_2H_2 P9) at 1530.37nm was used as the frequency reference. Then, the dispersion-like frequency discriminating curve was obtained by subtracting the two shifted absorption spectra of acetylene. The new method could avoid the extra frequency noise due to indirect frequency modulation of laser source in a conventional scheme. After locking laser, the typical frequency jitter was less than 5.8MHz in 50s, which is significantly better than the frequency fluctuation under free-running condition. Hence, the frequency stabilization of external cavity diode laser with a modulation-free output can be realized.