密集波分复用激光光源的声光偏频无调制频率锁定

Modulation-Free Laser Frequency Locking by Acousto-Optic Frequency-Shifting for Dense Wavelength Division Multiplexing

利用声光调制器（AOM）的偏频特性,以CH4分子吸收线R9支一条强吸收线（λ=1.6378μm）作为参考频率,实现了对外腔式半导体激光器的无调制频率锁定。实验中在100 s内典型的频率起伏小于5.6 MHz,较激光器自由运转时的频率起伏34 MHz有了显著的改善,而误差信号的阿仑（Allan）方差平方根（即稳定度）在平均积分时间为16 s时达到最小值5.75×10^-10。该方法实现了基于气体分子吸收线的半导体激光器无调制锁频,并且CH4分子在1.6-1.7μm处有丰富的振转光谱,满足光纤通信中对激光器输出波长的要求,可应用于光纤通信中激光光源的频率锁定。

By use of an acousto-optic modulator （AOM） to shift the laser frequency and the molecular absorption line of CH4 around 1. 6378 μm as the frequency reference, an external cavity diode laser was frequency-locked free of modulation. In experiment, the typical laser frequency jitter less than 5.6 MHz is achieved in 100 s, which is greatly improved comparing with the frequency fluctuation of about 34 MHz in the condition of free running, and the square root of Allan variance of error signals reaches a minimum of 5.75×10^-10 when the averaging time is 16 s. The modulation free frequency locking of diode laser based on modular absorption line is achieved. And because of the rich rotation-vibration lines of CH4 from 1.6 to 1.7 μm, it can fulfill laser wavelength in fiber-optic communication and be used for frequency locking.