Normal--mode splitting in a weakly coupled optomechanical system

TL;DR

This paper demonstrates that a weakly coupled optomechanical system at room temperature can exhibit normal-mode splitting, a signature of strong coupling, by using phase-sensitive feedback to reduce effective decay rates.

Contribution

It introduces a method to observe normal-mode splitting in weakly coupled systems via feedback control, effectively achieving strong coupling conditions.

Findings

Normal-mode splitting observed at room temperature.

Feedback loop reduces effective cavity decay rate.

Weakly coupled system behaves as strongly coupled.

Abstract

Normal--mode splitting is the most evident signature of strong coupling between two interacting subsystems. It occurs when two subsystems exchange energy between themselves faster than they dissipate it to the environment. Here we experimentally show that a weakly coupled optomechanical system at room temperature can manifest normal--mode splitting when the pump field fluctuations are anti-squashed by a phase-sensitive feedback loop operating close to its instability threshold. Under these conditions the optical cavity exhibits an effectively reduced decay rate, so that the system is effectively promoted to the strong coupling regime.