原子干涉仪中拉曼激光的相位-频率双调制稳频

Phase-frequency double-modulation frequency stabilization of Raman laser in atom interferometer

为降低拉曼激光的频率噪声,提出了一种相位-频率双调制稳频技术。用光纤电光相位调制器对激光进行调制并产生大失谐边带;用射频信号对光纤相位调制器的微波驱动信号进行频率调制,通过锁相放大法将一个大失谐边带锁到铷原子的饱和吸收谱线上。利用该技术实现了拉曼种子激光的稳频和2 GHz的移频,将拉曼激光的线宽大幅压窄到56 kHz,预期拉曼激光频率噪声引起的原子干涉重力仪的单次测量噪声可降低到7×10^(-9)s^(-2)。

In order to reduce the frequency noise of Raman laser, a phase-frequency double-modulation frequency stabilization technique is proposed. The laser is modulated by a fiber electro-optical phase modulator （F-EOM） and large-detuned sidebands are produced. Radio-frequency（RF） signal is used for frequency modulation of the microwave driving signal of F-EOM, and one of the large-detuned sidebands is locked to a saturation absorption spectral line of rubidium atoms by lock-in amplification. The frequency stabilization and 2 GHz frequency shift of Raman seed laser are realized by using this technique, and the linewidth of Raman laser is narrowed down to 56 kHz. The single measurement noise of atom gravity interferometer induced by Raman laser frequency noise is expected to be reduced to 7 × 10^-9 s^-2.