Linear and nonlinear capacitive coupling of electro-opto-mechanical photonic crystal cavities

TL;DR

This paper demonstrates a silicon electro-opto-mechanical system with strong capacitive coupling, enabling efficient microwave-to-optical signal conversion through integrated mechanical, electrical, and optical interactions.

Contribution

The authors introduce a fabrication method for creating nanoscale capacitor gaps in silicon photonic structures, enhancing electromechanical coupling for signal conversion.

Findings

Capacitor gaps as small as 30 nm achieved.

Strong linear and nonlinear capacitive coupling characterized.

Potential for efficient microwave-to-optical conversion demonstrated.

Abstract

We fabricate and characterize a microscale silicon electro-opto-mechanical system whose mechanical motion is coupled capacitively to an electrical circuit and optically via radiation pressure to a photonic crystal cavity. To achieve large electromechanical interaction strength, we implement an inverse shadow mask fabrication scheme which obtains capacitor gaps as small as 30 nm while maintaining a silicon surface quality necessary for minimizing optical loss. Using the sensitive optical read-out of the photonic crystal cavity, we characterize the linear and nonlinear capacitive coupling to the fundamental 63 MHz in-plane flexural motion of the structure, showing that the large electromechanical coupling in such devices may be suitable for realizing efficient microwave-to-optical signal conversion.