Gereration of microwaves with ultra-low phase-noise from an optical clock

Frequency stabilized lasers have significant advantages for generating microwave signals with unprecedented stability and ultralow phase-noise. We report the optical generation of 10 GHz microwave signals with phase-noise close to the carrier that is > 40 dB better than achieved with state-of-the-art microwave sources and high quality microwave synthesizers. The method uses stable lasers locked to optical resonators that have extremely high Q's and the frequency can be steered in the longer term to atomic resonances. An optical frequency divider is implemented with a femtosecond laser based optical frequency comb, which coherently divides the optical frequency to the microwave range