Phonon laser action in a tunable, two-level photonic molecule

TL;DR

This paper demonstrates a tunable phonon laser using a coupled microcavity system, achieving phonon amplification analogous to optical lasers, with potential for switching between phonon and photon laser regimes and cooling the mechanical mode.

Contribution

It introduces a novel phonon laser system based on a two-level microcavity setup with tunable gain spectrum, enabling controlled phonon amplification and mode switching.

Findings

Phonon laser action observed above 50 μW pump power.

Device achieves tunable gain spectrum for mechanical mode amplification.

System can switch between phonon and photon laser regimes.

Abstract

The phonon analog of an optical laser has long been a subject of interest. We demonstrate a compound microcavity system, coupled to a radio-frequency mechanical mode, that operates in close analogy to a two-level laser system. An inversion produces gain, causing phonon laser action above a pump power threshold of around 50 $\mu$W. The device features a continuously tunable, gain spectrum to selectively amplify mechanical modes from radio frequency to microwave rates. Viewed as a Brillouin process, the system accesses a regime in which the phonon plays what has traditionally been the role of the Stokes wave. For this reason, it should also be possible to controllably switch between phonon and photon laser regimes. Cooling of the mechanical mode is also possible.