Optical dilution and feedback cooling of a gram-scale oscillator to 6.9 mK

TL;DR

This study demonstrates cooling of a 1-gram oscillator to 6.9 mK using optical spring effects combined with active feedback, significantly reducing thermal noise and increasing coherence time.

Contribution

It introduces a method combining optical dilution via the optical spring effect with feedback cooling to achieve unprecedented low temperatures in a gram-scale oscillator.

Findings

Achieved a minimum temperature of 6.9 mK, 40,000 times below environmental temperature.

Increased the dynamical lifetime of the oscillator state by a factor of 200.

Demonstrated optical spring effect enhances coherence and cooling performance.

Abstract

We report on use of a radiation pressure induced restoring force, the optical spring effect, to optically dilute the mechanical damping of a 1 gram suspended mirror, which is then cooled by active feedback (cold damping). Optical dilution relaxes the limit on cooling imposed by mechanical losses, allowing the oscillator mode to reach a minimum temperature of 6.9 mK, a factor of ~40000 below the environmental temperature. A further advantage of the optical spring effect is that it can increase the number of oscillations before decoherence by several orders of magnitude. In the present experiment we infer an increase in the dynamical lifetime of the state by a factor of ~200.