Novel techniques for low-noise microwave generation and transfer of spectral purity with optical frequency combs

Low phase noise microwave signals are of prime im-portance for a variety of applications, from radar and tele-communication to synchronization of large instruments (e.g. VLBI, FEL) and time-keeping primary frequency standards. By phase locking a self-references optical frequency comb (OFC) to a state-of-the-art ultra-stable laser, and photo-detection the train of pulses of the femtosecond laser that lies at the heart of the frequency comb, one establishes a phase coherent link between the optics and microwave. The photo-generated microwave signal´s phase is a frequency down-converted copy of that of the ultra-stable laser with, in the ideal mathematics case a noise strongly reduced (-86dB for a transfer between a 200THz continuous laser and a 10GHz microwave signal). The excess noise that is inevita-bly added by the OFC-based transfer can be made very small by applying several techniques that I will be describing in this presentation.