An integrated low phase noise radiation-pressure-driven optomechanical oscillator chipset

TL;DR

This paper presents a CMOS-compatible integrated optomechanical oscillator chipset with ultra-low phase noise, capable of generating multiple frequency tones, suitable for high-precision RF photonic applications.

Contribution

It demonstrates the first monolithic integration of high-quality photonic crystal optomechanical oscillators with on-chip high-speed Ge detectors on a silicon CMOS platform.

Findings

Achieved phase noise as low as -125 dBc/Hz at 10 kHz offset.

Generated high harmonics up to 59th order and subharmonics down to 1/4.

Operates effectively at room temperature and atmospheric conditions.

Abstract

High-quality frequency references are the cornerstones in position, navigation and timing applications of both scientific and commercial domains. Optomechanical oscillators, with direct coupling to continuous-wave light and non-material-limited f Q product, are long regarded as a potential platform for frequency reference in radio-frequency-photonic architectures. However, one major challenge is the compatibility with standard CMOS fabrication processes while maintaining optomechanical high quality performance. Here we demonstrate the monolithic integration of photonic crystal optomechanical oscillators and on-chip high speed Ge detectors based on the silicon CMOS platform. With the generation of both high harmonics (up to 59th order) and subharmonics (down to 1/4), our chipset provides multiple frequency tones for applications in both frequency multipliers and dividers. The phase noise is measured down to -125 dBc/Hz at 10 kHz offset at ~ 400 {\mu}W dropped-in powers, one of the lowest noise optomechanical oscillators to date and in room-temperature and atmospheric non-vacuum operating conditions. These characteristics enable optomechanical oscillators as a frequency reference platform for radio-frequency-photonic information processing.