多频率合成主动抑制激光稳频的剩余幅度调制

Active Suppression of Residual Amplitude Modulation in Laser Frequency Stabilization by Multi-Frequency Mixing

宽带波导型电光调制器(EOM)可以施加多个频率射频信号,通过3个频率的合成,在激光载波上调制出3对边带。利用这3对边带某一侧的3个频率信号进行Pound-Drever-Hall(PDH)频率锁定实验,通过调整其中某一个频率信号的相位,可以实现对频率锁定误差信号基线的调整。频率锁定系统中的剩余幅度调制(RAM)噪声同样造成误差信号基线的漂移,通过主动反馈控制系统调制频率信号的相位,实现了对剩余幅度调制噪声的抑制。实验表明,在主动反馈系统闭环后,对剩余幅度调制噪声的抑制程度达到30 d B以上,并有效地抑制了噪声漂移。

A wideband waveguide electro-optical modulator（EOM） is driven by multiple frequencies signal. By synthesizing three frequencies and using these frequencies to drive the wideband waveguide EOM, three pairs of sidebands are added to the carrier laser frequency. Three sidebands on one single side of the carrier are used to laser frequency stabilization by Pound-Drever-Hall（PDH） technique. By adjusting the phase of one frequency signal,the baseline drift of the PDH error signal is controlled. The residual amplitude modulation（RAM） noise in frequency locking system also causes error signal baseline drift, through active phase modulation frequency signal feedback control system, the residual amplitude modulation noise suppression is realized. Experimental results show that after applying the active closed loop feedback system, the RAM noise is suppressed over 30 d B, and noise drift is suppressed effectively.