Optomechanical microwave oscillator and frequency comb generation in a full phononic bandgap 1D optomechanical crystal cavity

摘要

In this work we show that a silicon optomechanical crystal cavity can be used as an optomechanical oscillator when driven to the phonon lasing condition with a blue-detuned laser. The optomechanical cavity is designed to have a breathing like mode vibrating at Ω_m/2π =3.897 GHz in a full phononic bandgap. Our measurements show that the first harmonic displays a phase noise of -100 dBc/Hz at 100 kHz. Stronger blue-detuned driving leads eventually to the formation of an optomechanical frequency comb, with lines spaced by the mechanical frequency. The measured phase noise grows up with the harmonic number, as in classical harmonic mixing. We present real-time measurements of the comb waveform and show that it can be adjusted to a theoretical model recently presented. Our results suggest that silicon optomechanical cavities can play a role in integrated microwave photonics.