Ultrahigh precision synchronization of optical and microwave frequency sources

In this paper we demonstrate that balanced optical-microwave phase detectors (BOMPD) are able to provide a robust long-term optical-RF synchronization with sub-femtosecond residual timing drift over 24 hours in laboratory conditions without active temperature control of optical and electronic paths. Moreover, 10.833 GHz Sapphire-loaded cavity oscillator (SLCO) was successfully disciplined by 216.66 MHz laser oscillator using theBOMPD which resulted in a sub-femtosecond RMS jitter integrated from 1 Hz to 1 MHz.