Photonic Microwave Oscillator based on an Ultra-stable-laser and an Optical Frequency Comb

We present a transportable photonic microwave oscillator, porting optical stability to a 10 GHz microwave signal. The system is composed of two main sub-units: a compact 8 height-unit (HU) 194 THz ultra-stable laser with Hz linewidth showing a fractional frequency stability (modified Allan deviation) of 8.5 × 10-15 at 1 s and a 3 HU ultra-low noise optical frequency comb used to phase-coherently divide the optical frequency reference’s spectral purity down to a 10 GHz microwave signal. Characterizing the synthesized microwave by means of a commercial digital cross-correlator, a phase noise power spectral density of -70 dBc/Hz at 1 Hz and -160 dBc/Hz at 10 kHz Fourier frequency is measured, maintaining a white plateau at -165 dBc/Hz up to 10 MHz offset.