A Monolithic Radiation-Pressure Driven, Low Phase Noise Silicon Nitride Opto-Mechanical Oscillator

TL;DR

This paper introduces a CMOS-compatible silicon nitride opto-mechanical oscillator with low phase noise, achieved through integrated grating couplers, eliminating the need for external coupling and complex fabrication processes.

Contribution

The work presents a novel CMOS-compatible fabrication process for high-Q silicon nitride resonators with integrated coupling, enabling low phase noise radiation-pressure driven oscillators.

Findings

Operates at 41.97 MHz with -11 dBm signal power

Achieves phase noise of -85 dBc/Hz at 1 kHz offset

Displays 1/f^2 noise down to 10 Hz offset

Abstract

Cavity opto-mechanics enabled radiation pressure (RP) driven oscillators shown in the past offer an all optical Radio Frequency (RF) source without the need for external electrical feedback. However these oscillators require external tapered fiber or prism coupling and non-standard fabrication processes. In this work, we present a CMOS compatible fabrication process to design high optical quality factor opto-mechanical resonators in silicon nitride. The ring resonators designed in this process demonstrate low phase noise RP driven oscillations. Using integrated grating couplers and waveguide to couple light to the micro-resonator eliminates 1/f^3 and other higher order phase noise slopes at close-to-carrier frequencies present in previous demonstrations. We present an RP driven OMO operating at 41.97MHz with a signal power of -11dBm and phase noise of -85dBc/Hz at 1kHz offset with only 1/f^2 noise down to 10Hz offset from carrier.