Magic cancellation point for vibration resilient ultrastable microwave signal synthesis

Photonically-synthesized microwave signals have surpassed the phase-noise performance achievable by traditional means of RF signal generation. However, for microwave-photonic oscillators to truly replace their RF counterparts, this phase-noise advantage must also be realizable when operating outside of a laboratory. Oscillators are known to be notoriously vibration sensitive, with both traditional RF and optical oscillators degrading sharply in all but the most stationary of environments. We demonstrate here a powerful technique that makes use of a precise frequency difference between two optical signals, termed the magic cancellation point, to suppress the vibration-induced noise upon optical frequency division to the RF. We showcase the cancellation of vibration noise by 22.6 dB, achieving an acceleration sensitivity of 1.5 × 10−10 g−1. Beyond mitigating the effects of vibration, this technique also preserves the excellent phase noise obtained by optical frequency division and reaches −72 dBc/Hz and −139 dBc/Hz at 10 Hz and 10 kHz offset frequencies on a 10 GHz carrier. This technique applies widely to optical carriers of any center wavelength and derived from an arbitrary resonator geometry.