基于^(85)Rb 5S_(1/2)→6P_(3/2)的小型超稳铷原子光频标

Compact ultrastable Rb optical frequency standard based on ^(85)Rb 5S_(1/2)→6P_(3/2)

传统的铷原子钟主要是工作在微波频段,系统结构简单可靠,但受限于钟跃迁频率,其频率稳定度很难进入10^(-14)量级水平。利用^(85)Rb基态5S_(1/2)与第二激发态6P_(3/2)之间的跃迁作为钟跃迁,并结合高信噪比的调制转移谱稳频技术和高速环路锁定,直接将420nm激光输出频率稳定在铷原子的超精细跃迁谱线上,实现将传统的铷原子微波钟拓展到铷原子光钟。通过自评估的方法,得到该系统的秒级频率稳定度为1.6×10^(-14),接近微波钟的量子极限,与目前国际上最好的532nm碘分子光频标性能相当。

Traditional Rb atomic clocks are working at microwave frequency range. The clock system is compact,but its frequency stability is hard to reach at 10-14 level limited by the absolute clock transition frequency. This paper proposes a new scheme expanding the Rb microwave atomic clock to Rb optical clock. The SSRb 5S1/2→6P3/2 transition （420 nm） is employed as the clock transition and the high signal-to -noise-ratio modulation transfer spectroscopy is used for frequency locking with the high-speed loop circuit. By self-comparison method, the stability of the Rb optical frequency standard has reached 1. 6 × 10 14/√τ,which has approached the quantum limit of microwave atomic clocks and is comparable with the best 532 nm iodine frequency standard of the world.