Remark on laser linewidth hazard in opto-mechanical cooling

TL;DR

This paper highlights the extreme sensitivity of opto-mechanical cooling to laser phase noise, showing that achieving ground state cooling with a single cavity demands unrealistically narrow laser linewidths, and discusses interferometric twin-cavity pumping as a noise mitigation method.

Contribution

It analyzes the impact of laser phase diffusion on opto-mechanical cooling and proposes interferometric twin-cavity pumping to cancel classical phase noise.

Findings

Opto-mechanical cooling is more sensitive to phase noise than atomic laser cooling.

Single cavity ground state cooling requires unrealistically narrow laser linewidths.

Interferometric twin-cavity pumping can cancel classical excess phase noise.

Abstract

I discuss the robustness of the pumped cavity dynamics against phase diffusion of the laser and conclude that opto-mechanical cooling has extreme sensitivity compared to laser cooling of atoms. Certain proposals of ground state opto-mechanical cooling by single cavity would require an unrealistic sharp laser linewidth or equivalently, a very low level of phase noise. A systematic way to cancel classical excess phase noise is the interferometric twin-cavity pumping, initiated for optically trapped macro-mirrors of future gravitational-wave detectors.