Strong optomechanical interactions in a sliced photonic crystal nanobeam

TL;DR

This paper demonstrates a sliced photonic crystal nanobeam with exceptionally strong optomechanical coupling, enabling sensitive motion detection and control at the quantum level in a compact system.

Contribution

The work introduces a nanoscale optomechanical system with a coupling rate ten times higher than previous systems, combining subwavelength optical confinement with low-mass mechanical modes.

Findings

Coupling rate g0/2π = 11.5 MHz, surpassing previous records.

Achieved motion detection below the standard quantum limit noise.

System maintains high sensitivity despite low optical and mechanical quality factors.

Abstract

Cavity optomechanical systems can be used for sensitive detection of mechanical motion and to control mechanical resonators, down to the quantum level. The strength with which optical and mechanical degrees of freedom interact is defined by the photon-phonon coupling rate $g_0$, which is especially large in nanoscale systems. Here, we demonstrate an optomechanical system based on a sliced photonic crystal nanobeam, that combines subwavelength optical confinement with a low-mass mechanical mode. Analyzing the transduction of motion and effects of radiation pressure we find a coupling rate $g_0$/2{\pi} = 11.5 MHz, exceeding previously reported values by an order of magnitude. Using this interaction we detect the resonator's motion with a noise imprecision below that at the standard quantum limit, even though the system has optical and mechanical quality factors smaller than $10^3$. The broad bandwidth is useful for application in miniature sensors, and for measurement-based control of the resonator's motional state.