High-frequency silicon optomechanical oscillator with an ultralow threshold.

We demonstrate a highly efficient optomechanical oscillator based upon a small silicon microdisk resonator with a 2-μm radius. The device exhibits a strong optomechanical coupling of 115 GHz/nm and a large intrinsic mechanical frequency-Q product of 4.32 × 10(12) Hz. It is able to operate at a high frequency of 1.294 GHz with an ultralow threshold of 3.56 μW while working in the air environment. The high efficiency, high frequency together with the structural compactness and CMOS compatibility of our device enables great potential for broad applications in photonic-phononic signal processing, sensing, and metrology.