Integrated optical-readout of a high-Q mechanical out-of-plane mode

TL;DR

This paper introduces a versatile fabrication method for integrated optomechanical structures that combine high-Q mechanical resonators with photonic crystal cavities, enabling strong optical-mechanical coupling suitable for quantum applications.

Contribution

The authors develop a scalable, integrated approach to combine high-Q mechanical modes with optical read-out, enhancing optomechanical interaction strengths and device versatility.

Findings

Successfully integrated high-Q mechanical resonators with photonic crystal cavities

Achieved large cavity photon numbers for enhanced optomechanical interactions

Method scalable to large arrays and adaptable to various device layouts

Abstract

The rapid development of high-Q macroscopic mechanical resonators has enabled great advances in optomechanics. Further improvements could allow for quantum-limited or quantum-enhanced applications at ambient temperature. Some of the remaining challenges include the integration of high-Q structures on a chip, while simultaneously achieving large coupling strengths through an optical read-out. Here, we present a versatile fabrication method, which allows us to build fully integrated optomechanical structures. We place a photonic crystal cavity directly above a mechanical resonator with high-Q fundamental out-of-plane mode, separated by a small gap. The highly confined optical field has a large overlap with the mechanical mode, enabling strong optomechanical interaction strengths. Furthermore, we implement a novel photonic crystal design, which allows for a very large cavity photon number, a highly important feature for optomechanical experiments and sensor applications. Our versatile approach is not limited to our particular design but allows for integrating an out-of-plane optical read-out into almost any device layout. Additionally, it can be scaled to large arrays and paves the way to realizing quantum experiments and applications with mechanical resonators based on high-Q out-of-plane modes alike.