Radiation-pressure self-cooling of a micromirror in a cryogenic environment

TL;DR

This paper demonstrates radiation-pressure cavity cooling of a micromirror's mechanical mode from cryogenic temperatures, achieving significant cooling without heating effects, advancing towards quantum ground state cooling.

Contribution

First demonstration of cavity cooling of a micromirror's mechanical mode starting from cryogenic temperatures with high finesse cavity stabilization.

Findings

Cooling from 35 K to 290 mK achieved

Thermal occupation factor reduced to <n>=10^4

No heating effects observed during cooling

Abstract

We demonstrate radiation-pressure cavity-cooling of a mechanical mode of a micromirror starting from cryogenic temperatures. To achieve that, a high-finesse Fabry-Perot cavity (F\approx 2200) was actively stabilized inside a continuous-flow 4He cryostat. We observed optical cooling of the fundamental mode of a 50mu x 50 mu x 5.4 mu singly-clamped micromirror at \omega_m=3.5 MHz from 35 K to approx. 290 mK. This corresponds to a thermal occupation factor of <n>\approx 1x10^4. The cooling performance is only limited by the mechanical quality and by the optical finesse of the system. Heating effects, e.g. due to absorption of photons in the micromirror, could not be observed. These results represent a next step towards cavity-cooling a mechanical oscillator into its quantum ground state.