利用偏振光谱对外腔式半导体激光器实现无调制锁频

Frequency Stabilization of an External Cavity Diode Laser Using Polarization Spectroscopy without Frequency Modulation

将激光器输出频率相对于合适的参考频率标准进行锁定,可以有效地抑制激光器的频率起伏,提高激光器的频率稳定度。对铯原子偏振光谱进行平衡探测,当偏振光谱透射方向与偏振分束棱镜(PBS)偏振面之间的夹角选择合适时,平衡探测后的输出信号即为铯原子D2跃迁线的色散形鉴频信号。实验上实现了波长为852 nm的外腔式半导体激光器对应于铯原子6S1/2(F=4)→6P3/2(F′=5)超精细跃迁线的频率锁定。研究获得在50 s内激光器频率起伏小于±250 kHz,较相同时间内激光器自由运转时的频率起伏3 MHz有显著改善。这种频率锁定的方法不需要对激光器进行调制。

Locking the output frequency of laser to an available referential frequency standard can efficiently suppress the fluctuation of frequency and improve the frequency stability of laser. Through the balance probe for polarization spectrum of cesium atoms, when the angle of the transmission axis of the polarization spectrum tilted with respect to the polarization axis of polarization beam splitter （PBS） is appropriate, then the achieved signal is just the dispersion frequency discrimination error signal of cesium atoms D2 transition line. In experiment, an external cavity diode laser with 852 nm wavelength is locked to the hyperfine component of cesium atoms 6S1/2 （F = 4） → 6P3/2 （F′ = 5）. By locking the laser the frequency jitter of less than±250 kHz is achieved in 50 s, which is greatly improved comparing with the frequency fluctuation of about 3 MHz in the condition of free-running. This technique does not need to modulate the laser.