Phonon-phonon interaction as a control knob for multimode splitting in a two mirror parametrically assisted optomechanical cavity

TL;DR

This paper demonstrates how phonon-phonon interactions can be used to control and enhance multimode splitting in a two-mirror optomechanical cavity with an intracavity parametric amplifier.

Contribution

It reveals that direct mechanical coupling can significantly modify the normal-mode spectrum, enabling better spectral resolution and control in optomechanical systems.

Findings

Finite phonon-phonon coupling mixes mechanical modes, making a third resonance resolvable.

The spectral changes are more pronounced with increased coupling strength and drive power.

Mechanical coupling tuning enhances multimode hybridization and spectral visibility.

Abstract

We study a driven optomechanical cavity with two movable mirrors and an intracavity optical parametric amplifier, focusing on how direct phonon-phonon coupling changes the observed normal-mode spectrum. Although the linearized system supports three hybrid modes, in the absence of direct mechanical coupling one collective mechanical mode contributes only weakly to the optical response, leading to an apparent two-peak structure. We show that finite phonon-phonon coupling mixes this weakly participating mode with the optically visible modes, making a third resonance clearly resolvable. This change appears in the mirror displacement spectrum, the output-field spectrum, and the output quadrature spectra, and becomes more pronounced with increasing coupling strength and drive power. Our results show that direct mechanical coupling provides a useful way to tune spectral visibility and multimode hybridization in two-mirror optomechanical cavity with intracavity parametric amplification.