"Membrane-outside" as an optomechanical system

TL;DR

This paper proposes a novel optomechanical system with a membrane outside a cavity, demonstrating conditions where dissipative coupling dominates over dispersive coupling, enabling strong dissipative interactions and quantum measurements without instability.

Contribution

It introduces a new configuration with a membrane outside the cavity that achieves dominant dissipative coupling, surpassing traditional systems in strength and stability.

Findings

Dissipative coupling exceeds dispersive coupling under specific transmission conditions.

The system enables quantum-limited measurements without optomechanical instability.

Compared favorably with Michelson-Sagnac and membrane-at-the-edge setups.

Abstract

We theoretically study an optomechanical system, which consists of a two-sided cavity and a mechanical membrane that is placed outside of it. The membrane is positioned close to one of its mirrors, and the cavity is coupled to the external light field through the other mirror. Our study is focused on the regime where the dispersive optomechanical coupling in the system vanishes. Such a regime is found to be possible if the membrane is less reflecting than the adjacent mirror, yielding a potentially very strong dissipative optomechanical coupling. Specifically, if the absolute values of amplitude transmission coefficients of the membrane and the mirror, $t$ and $t_m$ respectively, obey the condition $ t_m^2< t\ll t_m\ll 1$, the dissipative coupling constant of the setup exceeds the dispersive coupling constant for an optomechanical cavity of the same length. The dissipative coupling constant and the corresponding optomechanical cooperativity of the proposed system are also compared with those of the Michelson-Sagnac interferometer and the so-called "membrane-at-the-edge" system, which are known for a strong optomechanical dissipative interaction. It is shown that under the above condition, the system proposed here is advantageous in both aspects. It also enables an efficient realization of the two-port configuration, which was recently proposed as a promising optomechanical system, providing, among other benefits, a possibility of quantum limited optomechanical measurements in a system, which does not suffer from any optomechanical instability.