Coherent mixing of mechanical excitations in nano-optomechanical structures

TL;DR

This paper explores how strong optical forces in nanocavity optomechanical systems enable control and coherent transfer of mechanical excitations, demonstrating optical rigidity, mode hybridization, and a form of optically-controlled mechanical transparency.

Contribution

It introduces a method to manipulate mechanical modes via optical forces in nanocavities, including the creation of bright and dark modes and a proposal for RF/microwave signal transfer.

Findings

Optical forces induce significant mechanical mode renormalization.

Demonstration of optically-controlled mechanical transparency.

Proposal for coherent RF/microwave signal transfer using dark mechanical states.

Abstract

The combination of large per-photon optical force and small motional mass attainable in nanocavity optomechanical systems results in strong dynamical back-action between mechanical motion and the cavity light field. In this work we study the optical control of mechanical motion within two different nanocavity structures, a zipper nanobeam photonic crystal cavity and a double-microdisk whispering-gallery resonator. The strong optical gradient force within these cavities is shown to introduce signifcant optical rigidity into the structure, with the dressed mechanical states renormalized into optically-bright and optically-dark modes of motion. With the addition of internal mechanical coupling between mechanical modes, a form of optically-controlled mechanical transparency is demonstrated in analogy to electromagnetically induced transparency of three-level atomic media. Based upon these measurements, a proposal for coherently transferring RF/microwave signals between the optical field and a long-lived dark mechanical state is described.