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在使用铷原子饱和吸收谱线作为激光频率参考进行稳频的激光稳频系统中,环路带宽是影响激光输出频率噪声的重要因素之一。对激光稳频系统中限制环路带宽的主要因素进行分析,使用射频调制信号直接调制商用外腔半导体激光器的高速电流调制端来对激光稳频系统的环路带宽进行拓展。根据对稳频环路的分析,合理设置反馈电路,实现激光稳频。使用低频谱分析仪对稳频后的鉴频信号进行分析,发现带宽拓展后,在傅里叶频率为5kHz处对频率噪声的抑制度达到了20dB以上。通过将该稳频激光器输出的激光与锁定在极稳恒温晶振上的飞秒光学频率梳进行拍频,测量了该稳频激光相对光梳的频率噪声,测量结果与直接分析鉴频信号的结果吻合。经过测量,通过拓展带宽抑制频率噪声,稳频激光器的短期频率稳定度得到改善。最后,测量了稳频激光相对于锁定在恒温晶振上的飞秒光学频率梳的频率稳定度,Allan方差在平均时间1s时达到4.52×10~(-12),在平均时间20s时达到1.65×10~(-12)。
In the laser frequency stabilization system using the RBWR as the laser frequency reference, the loop bandwidth is one of the important factors affecting the laser output frequency noise. The main factors limiting the loop bandwidth in the laser frequency stabilization system are analyzed, and the high-speed current modulation terminal of the commercial external semiconductor laser is directly modulated by the RF modulation signal to expand the loop bandwidth of the laser frequency stabilization system. According to the analysis of the frequency stabilization loop, a reasonable set of feedback circuit to achieve laser frequency stabilization. The analysis of the frequency-discriminated frequency-discriminating signal with a low-frequency spectrum analyzer shows that when the bandwidth is expanded, the suppression of the frequency noise at the frequency of 5 kHz at the Fourier frequency reaches more than 20 dB. The frequency noise of the frequency-stabilized laser beam relative to the optical comb was measured by beat-frequency of the laser output from the frequency-stabilized laser and the femtosecond optical frequency comb locked on a crystal oscillator with very stable temperature. The results of the measurement and the direct analysis of the frequency-discriminating signal Anastomosis. After measurement, short-term frequency stability of the frequency stabilized laser is improved by expanding the bandwidth-suppressed frequency noise. Finally, the frequency stability of the frequency-stabilized laser relative to the femtosecond optical frequency comb locked in the thermostatic crystal was measured. The Allan variance reached 4.52 × 10 ~ (-12) at the average time of 1s and 1.65 × at the average time of 20s 10 ~ (-12).