Optomechanical cooling in a continuous system

TL;DR

This paper demonstrates the first optomechanical cooling in a continuous waveguide system, using Brillouin scattering to cool traveling phonons without a cavity, enabling new control over phonons in extended systems.

Contribution

It introduces a novel method for optomechanical cooling in a continuous waveguide, expanding the scope of cavity optomechanics to macroscopic linear systems without discrete modes.

Findings

Achieved over 30 K cooling of traveling phonons from room temperature.

Demonstrated nonreciprocal reservoir engineering in a waveguide system.

Enabled control over continuous groups of phonons via wavevector-resolved spectroscopy.

Abstract

Radiation-pressure-induced optomechanical coupling permits exquisite control of micro- and mesoscopic mechanical oscillators. This ability to manipulate and even damp mechanical motion with light---a process known as dynamical backaction cooling---has become the basis for a range of novel phenomena within the burgeoning field of cavity optomechanics, spanning from dissipation engineering to quantum state preparation. As this field moves toward more complex systems and dynamics, there has been growing interest in the prospect of cooling traveling-wave phonons in continuous optomechanical waveguides. Here, we demonstrate optomechanical cooling in a continuous system for the first time. By leveraging the dispersive symmetry breaking produced by inter-modal Brillouin scattering, we achieve continuous mode optomechanical cooling in an extended 2.3-cm silicon waveguide, reducing the temperature of a band of traveling-wave phonons by more than 30 K from room temperature. This work reveals that optomechanical cooling is possible in macroscopic linear waveguide systems without an optical cavity or discrete acoustic modes. Moreover, through an intriguing type of wavevector-resolved phonon spectroscopy, we show that this system permits optomechanical control over continuously accessible groups of phonons and produces a new form of nonreciprocal reservoir engineering. Beyond this study, this work represents a first step towards a range of novel classical and quantum traveling-wave operations in continuous optomechanical systems.