Doppler controlled dynamics of a mirror attached to a spring

TL;DR

This paper explores Doppler cooling and amplification of a mirror's motion using wavelength-dependent Bragg mirrors, revealing efficient cooling at the band stop edge and potential for self-oscillation through optical pumping.

Contribution

It demonstrates how Bragg mirrors can significantly enhance Doppler cooling efficiency and induce vibrational amplification, enabling new control methods for mechanical systems.

Findings

Doppler cooling efficiency is greatly improved with Bragg mirrors at the band stop edge.

Tuning laser wavelength near the Bragg mirror's short wavelength edge induces vibrational amplification.

The reflectivity dependence on wavelength enables both cooling and self-oscillation of the mirror.

Abstract

A laser beam directed at a mirror attached onto a flexible mount extracts thermal energy from its mechanical Brownian motion by Doppler effect. For a normal mirror the efficiency of this Doppler cooling is very weak and masked by laser shot-noise. We find that it can become very efficient using a Bragg mirror at the long wavelength edge of its band stop. The opposite effect of cooling opens new routes for optical pumping of mechanical systems: a laser pointing at a Bragg mirror and tuned at its short wavelength edge induces amplification of the vibrational excitation of the mirror leading eventually to its self-oscillation. This new effects rely on the strong dependency of the Bragg mirror reflectivity on the wavelength.