Sub-Hz Closed-Loop Electro-Optomechanical Oscillator with Gallium Phosphide Photonic Crystal Integrated on SoI Circuitry

We report on a newapproach of a low phase noise electro-optomechanicaloscillator directly working in the GHz frequency range. The developednanoscale oscillator is a one-dimensional photonic crystal made ofgallium phosphide (GaP), heterogeneously integrated on silicon-on-insulatorcircuitry. Based on the strong interaction between the optical modeat the telecommunication wavelength and the mechanical mode in GHz,ultra-pure mechanical oscillations are enabled and directly imprintedon an optical carrier. Further stabilization is achieved with a delayedoptoelectronic feedback loop using integrated electro-mechanical self-injection.We achieve a short-term stability of 0.7 Hz linewidth and a long-termstability with an Allan deviation below 10(-7) Hz/Hzat 10 s averaging time, which represents an important step towardfully integrated optomechanical oscillators. Integrability and thelow phase noise of this oscillator address some of the most importantneeds of optoelectronic oscillators and pave the way toward on-chipintegrated microwave oscillators for microwave applications such asRADARs.

Automated summary

We introduce a new method for a low phase noise electro-optomechanical oscillator working directly in the GHz frequency range. This nanoscale oscillator is made of gallium phosphide (GaP) and integrated on silicon-on-insulator circuitry. By utilizing the strong interaction between optical and mechanical modes, ultra-pure mechanical oscillations are achieved and imprinted on an optical carrier. Stabilization is accomplished with an integrated optoelectronic feedback loop, resulting in short-term stability with a linewidth of 0.7 Hz and long-term stability with an Allan deviation below 10(-7) Hz/Hz at 10 s averaging time.