Optomechanical coupling in a two-dimensional photonic crystal defect cavity

TL;DR

This paper experimentally investigates optomechanical interactions in a two-dimensional photonic crystal defect cavity, demonstrating strong coupling with vacuum coupling rates exceeding 250 kHz, and identifying both flexural and localized GHz mechanical modes.

Contribution

The study provides the first experimental measurement of optomechanical coupling in a 2D photonic crystal defect cavity with strong coupling rates.

Findings

Observation of flexural and localized GHz mechanical modes

Vacuum optomechanical coupling rate exceeds 250 kHz

Demonstration of strong optomechanical coupling in 2D photonic crystals

Abstract

Periodically structured materials can sustain both optical and mechanical modes. Here we investigate and observe experimentally the optomechanical properties of a conventional two-dimensional suspended photonic crystal defect cavity with a mode volume of $\sim$$3(\lambda/n)^{3}$. Two families of mechanical modes are observed: flexural modes, associated to the motion of the whole suspended membrane, and localized modes with frequencies in the GHz regime corresponding to localized phonons in the optical defect cavity of diffraction-limited size. We demonstrate direct measurements of the optomechanical vacuum coupling rate using a frequency calibration technique. The highest measured values exceed 250 kHz, demonstrating strong coupling of optical and mechanical modes in such structures.