采用萨尼亚克环的外腔半导体激光器无调制稳频技术

Modulation-free frequency stabilization system of external cavity diode laser based on Sagnac loop

提出了一种基于相位差偏置萨尼亚克环的新型外腔半导体激光(ECDL)无调制稳频方法,采用偏振分束器(PBS)作为萨尼亚克环的输入及输出端,并利用1/4波片在环内沿相反方向传播的偏振方向互相垂直的两束光之间引入π/2的相位差(△δ),萨尼亚克环的输出光经过起偏器可以分解得到由Rb的饱和吸收峰引起的色散相移,通过这种方法可以得到适合稳频的误差信号。相比现有的利用全内反射引入相位差(sin△δ=0.64)的方法,色散信号放大系数sin△δ的值可达到理论最大值,有效地提高了误差信号的强度,这种方法简单、稳健,且在原子物理实验等方面具有潜在应用。

A novel frequency stabilization method of ECDL using a phase difference biased Sagnac loop was proposed. This scheme uses polarization beam splitter （PBS） for input and output of Sagnac loop instead of the beam splitter, and a quarter waveplate to introduce a bias phase difference of π/2 between the counterpropagating pump and probe beams with perpendicular polarization. A polarizer is inserted after the output of the Sagnac loop, so that the dispersion phase shift induced by Rb resonance can be obtained. By this method, an error signal with larger amplitude can be acquired, which provides an ideal error signal to stabilize the frequency of the laser. Compared with the previously proposed method, whose bias phase difference is introduced by polarization dependent phase shift in total-internal-reflection （sinAi=0.64）, the amplification factors of dispersive signal sinA~ can be achieved to theoretical maximum. This scheme is simple, robust, and has potential applications in atomic physics experiment and so on.