Robust offset locking of laser frequency with electronically tunable LC circuits for sub-millihertz uncertainty

Abstract

A simple scheme for laser frequency offset locking introduced in Cheng et al. (Opt Express 25:2752, 2017) has been improved by the use of a variable-capacitance diode. By employing this scheme with the optical phase lock loop, robust and precise laser frequency stabilization is achieved, and long-term laser frequency drift is expected to be substantially suppressed even in noisy circumstances. The optical frequency uncertainty becomes less than 10 μ Hz for 1000 s averaging.