用前馈控制方法提高连续紫外激光器的调谐性和稳定性

Enhancement of Tunability and Stability of a Continuous-Wave Deep Ultraviolet Laser by Feed-Forward Control Method

连续可调谐的紫外激光一般通过红外或可见激光进行外腔倍频获得,然而倍频腔锁定电路的带宽限制了激光器的调谐性能。将前馈控制方法用于中性汞原子激光冷却的四倍频紫外激光器,即在调谐基频激光频率的同时,同步调节级联的两个倍频腔。这不仅降低了激光器频率调谐中引入的功率噪声,还提高了紫外激光器的频率调谐范围,使得紫外激光器的调谐能力得到大幅提高。通过汞原子的亚多普勒磁致双色光谱进行激光频率锁定,发现前馈控制电路的应用能降低激光的频率噪声。在汞原子光谱和激光冷却实验中,紫外激光的可调谐性和稳定性的提高将会带来很多优势。

Continuous-wave tunable deep ultraviolet （UV） laser is commonly realized by extra-cavity frequency doubling of near infrared ray （NIR） or visible laser, but the bandwidth of cavity locking circuits limits the tunability of laser. A feed-forward control method is applied in the frequency quadrupled UV laser, which is used for laser cooling of neutral mercury atom; that is to say, synchronous adjust ment two series frequency doubling cavity when tuning the frequency of fundamental laser. By this method, not only the power noise is induced by laser frequency tuning reduced, but also the frequency tuning range of the UV laser is enhanced. Hence, the tunability of UV laser is considerably increased. When the laser frequency on the Doppler-free dichroic locking spectroscopy of neutral mercury atom is locked, it is found that the laser frequency noise can be reduced by the application of feed-forward control circuit. The enhancement of the tunability and stability of UV laser provides a lot of advantages in the experiments of laser spectroscopy and laser cooling of mercury atom.