【摘要】 将激光器锁定到合适的参考频率标准上 ,可以有效地改善激光器的频率稳定性。采用两个声光调制器(AOM) ,使铯原子D2 线饱和吸收光谱分别发生Ω±Δ绝对频移 ;通过改变射频压控振荡器 (RFVCO)的Vf 端口直流电压调节相对频移间隔Δ ,当相对频率间隔选择合适时两信号相减得到了类色散型鉴频曲线。实验中实现了85 2nm光栅外腔半导体激光器相对于铯原子D2 线6S1/2 F =4 6P3 /2 F′ =5超精细跃迁线 (中心频率ν0 )的无调制偏频锁定 (锁定后中心频率ν0 +Ω ,偏频量为Ω)。由闭环锁定后的误差信号估计 ,5 0s内典型的频率起伏小于± 2 70kHz ,较相同时间段内激光器自由运转时的频率起伏 14MHz有显著的改善。该方法可避免对激光器直接进行频率调制的常规饱和吸收锁频方案所引入的额外频率噪声和强度噪声。更多还原

【Abstract】 Locking laser source to a proper frequency standard can obviously improve the laser’s frequency stability. Using two acousto-optic modulators (AOMs) to shift the saturation absorption spectra of cesium D 2 line by tuning the DC voltage of the radio frequency voltage controlled oscillator’s (RF VCO ) V f inputing port the AOM shifted sub-Doppler spectra were gotten, and dispersion-like frequency discriminating signal was obtained by subtracting the two relatively shifted sub-Doppler spectra. Modulation-free absolute frequency stabilization of an 852 nm grating-external-cavity diode laser was demonstrated with a frequency shifting of 80 MHz. Thanks to this modulation-free locking scheme, the typical frequency jitter of less than ±270 kHz in 50 s, relative to the cesium hyperfine transition of 6S 1/2 F=4 6P 3/2 YF′=5, was estimated in preliminary stabilization. The long-term frequency stability was greatly improved comparing with the frequency fluctuation of about 14 MHz under free-running condition in the same time scale. This scheme can avoid the extra frequency noise as well as intensity noise duo to the direct frequency dither on laser source in the conventional saturation absorption technique.更多还原