Laser frequency locking based on Rydberg electromagnetically induced transparency
Jiao Yuechun, Li Jingkui, Wang Limei, Zhang Hao, Zhang Linjie, Zhao Jianming†, , Jia Suotang
       

Square root of Allan variance as a function of averaging time, τ, for the coupling laser locking on (red circles) and free running (black squares). The measured minimum, σ(τ) with a measure interval of 0.1 s, is 6.3 × 10−10 for free-running and 8.9 × 10−11 for laser stabilization. The dashed line represents the theoretical curve.