Pulsed excitation dynamics of an optomechanical crystal resonator near its quantum ground-state of motion

TL;DR

This study employs pulsed optical techniques and single phonon counting to investigate the transient dynamics of a silicon optomechanical crystal near its quantum ground state, revealing low phonon occupancy and slow heating effects.

Contribution

It demonstrates the use of pulsed measurements to probe quantum optomechanical systems at millikelvin temperatures, highlighting low phonon occupancy and slow heating dynamics.

Findings

Initial phonon occupancy as low as 0.021

Intrinsic mechanical decay rate of 328 Hz

Slow (~740 ns) turn-on time for hot phonon bath

Abstract

Using pulsed optical excitation and read-out along with single phonon counting techniques, we measure the transient back-action, heating, and damping dynamics of a nanoscale silicon optomechanical crystal cavity mounted in a dilution refrigerator at a base temperature of 11mK. In addition to observing a slow (~740ns) turn-on time for the optical-absorption-induced hot phonon bath, we measure for the 5.6GHz `breathing' acoustic mode of the cavity an initial phonon occupancy as low as 0.021 +- 0.007 (mode temperature = 70mK) and an intrinsic mechanical decay rate of 328 +- 14 Hz (mechanical Q-factor = 1.7x10^7). These measurements demonstrate the feasibility of using short pulsed measurements for a variety of quantum optomechanical applications despite the presence of steady-state optical heating.