电光相位调制器中剩余幅度调制变化的抑制

Suppression of Fluctuation of Residual Amplitude Modulation in Electro-Optical Phase Modulators

实验研究了电光相位调制中剩余幅度调制以及它的变化引起的碘稳频532 nm光频标的频率漂移。观测了电光晶体温度与剩余幅度调制和光频标锁定后激光频率之间的变化关系。研究了利用主动电压反馈抑制剩余幅度调制的实际效果和存在问题。提出并实现了采用主动温度反馈控制电光晶体温度对剩余幅度调制变化的抑制。实验表明,在主动温度反馈系统闭环后,剩余幅度调制基波成分的抑制程度超过40 dB,同时有效地控制了剩余幅度调制的变化。采用该系统后,没有发现产生附加的激光频率起伏。测量的百秒至万秒取样时间的激光频率稳定度可达到或优于5×10-15,明显地改善了碘稳频532 nm光频标的中长期激光频率稳定度。

Residual amplitude modulation （RAM） in electro-optical phase modulators （EOM） and its influence on the laser frequency shift of iodine-stabilized 532 nm laser are investigated experimentally. The relationships between the EOM crystal temperature and the RAM, as well as stabilized laser frequency are observed. The effects and problems of using active voltage feedback method to suppress the RAM are researched. An active temperature feedback method is proposed and demonstrated to suppress the RAM fluctuation by controlling the EOM temperature. With this method the suppression of the fundamental component in the RAM spectra overtakes 40 dB. The RAM fluctuation is controlled effectively, and additional frequency fluctuation is induced from adopting the system. The laser frequency stability can achieve or be better than 5×10^-15 for the averaging time from 100 s to 104 s, and the stability of indine-stabilized 532 nm laser frequency in a medium and long term is improved greatly.