关键词: 主动光频标, 双波长好坏腔, 相位锁定技术, 剩余腔牵引效应

Abstract: The frequency stability of clock-transition laser in traditional passive optical clocks is ultimately limited by the Brownian noise,which is one of the main technical bottlenecks restricting the development of optical frequency standards.The active optical clock,utilizing the weak feedback of optical cavity to form coherent stimulated radiation between atomic-transition levels,is a novel laser.The atomic stimulated emission of active optical clock can be used as the clock-transition laser directly,therefore,compared with the passive part,the active optical clock can achieve narrower quantum limited linewidth and has the advantage of suppressed cavity-pulling effect.This paper reports the development of active optical frequency standards at home and abroad,and focus on its theoretical and experimental progress in Peking University.We proposed the dual-wavelength good-bad-cavity scheme to reduce the influence of the residual cavity-pulling effect on the Cesium(Cs)four-level active optical clock.The Nd:YAG 1 064 nm and Cs 1 470 nm lasers share one cavity and works in good- and bad-cavity regime,respectively.The good-cavity laser is frequency stabilized by the Pound-Drever-Hall(PDH)technique to stabilize the cavity length.Then the linewidth of the bad-cavity laser is expected to be further narrowed compared with the stabilized good-cavity laser,considering that the suppression of cavity-pulling effect in bad-cavity regime.Currently,the beating linewidth of 1 470 nm lasers is limited by the asynchronous change of cavity lengths of two dual-wavelength systems.In order to suppress the effect of common-mode noise of cavity-length on 1 470 nm beat-note signal,and verify the feasibility of PDH technique for cavity-length stabilization in dual-wavelength scheme,we put forward the phase locking technology to synchronize the cavity-length variation between two dual-wavelength systems.The influence of other factors besides residual cavity-pulling effect on 1 470 nm active optical frequency standard is further analyzed.

Key words: Active optical frequency standard, Dual-wavelength good-bad cavity, Phase locking technique, Suppressed cavity-pulling effect