Employing coupled cavities to increase the cooling rate of a levitated nanosphere in the resolved sideband regime

TL;DR

This paper explores how coupled cavities can enhance the cooling rate of a levitated nanosphere in the resolved sideband regime by increasing intra-cavity photon number and achieving strong coupling without higher laser power.

Contribution

It introduces a coupled cavity system that maximizes coupling strength at optimal detuning, improving cooling efficiency and strong coupling in the resolved sideband regime.

Findings

Enhanced cooling rate via coupled cavities

Achieved strong coupling without increased laser power

Validated analytical model with numerical simulations

Abstract

In this paper we investigate cooling of a levitated nanosphere in a system of coupled cavities in the resolved sideband regime. Thanks to the presence of an extra resonance in the coupled cavity cooling system, the coupling strength can be maximized at the optimum detuning. In this fashion, the intra-cavity photon number is increased and thereby the cooling rate is enhanced and the strong coupling regime is achieved without resorting to increased driving laser power. The underlying physics of the increased cooling efficiency in the here-proposed system of coupled cavities in the resolved sideband regime and that of the already reported system of coupled cavities in the unresolved sideband regime are significantly different from each other. Since the spectral density of the displacement of the particle can no longer be accurately approximated by the conventional Lorentzian lineshape in the strong coupling regime, a double Lorentzian lineshape is employed to accurately approximate the spectral density of the displacement of the particle and to provide analytical formulations for the cooling rate. The analytical expression given for the cooling rate is validated by numerical simulations.