Silicon opto-acoustic oscillator

The Opto-Electronic Oscillator (OEO) is state-of-the-art for generation of low-phase noise RF signals in the 1-30 GHz frequency range. The OEO uses a RF filter and an electro-optic modulator for filtering the RF signal and up-converting it to optical frequencies [1]. Our group has previously demonstrated a combined MEMS Acoustic filter + Optical modulator using silicon RF MEMS fabrication technology [2]. In this paper we report on improving the up-conversion loss of the Acousto-Optic modulator from -70dB to -26dB using an implant mask to reduce contact and series resistances. This low conversion loss enables us to close the optical and RF loops around the modulator, using an amplifier, to make an oscillator. This hybrid "Opto-Acoustic Oscillator\´\´ oscillates at 237 MHz with 5mW output power.