Quantum limit of laser cooling in dispersively- and dissipatively-coupled optomechanical systems

TL;DR

This paper derives an analytic expression for the quantum limit of laser cooling in optomechanical systems with combined dispersive and dissipative couplings, revealing how to optimize cooling performance.

Contribution

It provides the first analytic formula for the steady-state phonon number considering both dispersive and dissipative couplings in optomechanics.

Findings

Quantum limit of cooling is linked to optical force fluctuations.

Optimal cooling involves combining dispersive and dissipative couplings.

Minimal phonon number depends on coupling types and system parameters.

Abstract

Mechanical oscillators can be cooled by coupling them to an optical or microwave cavity. Going beyond the standard quantum noise approach we find an analytic expression for the steady-state phonon number in systems where the position of the mechanical oscillator modulates the cavity frequency as well as the cavity line width. We trace the origin for the quantum limit of cooling to fluctuations in the optical force both at and away from the mechanical frequency. Finally, we calculate the minimal phonon number for the different types of coupling. Our study elucidates how to beneficially combine dispersive and dissipative optomechanical coupling.