Cavity-less Brillouin strong coupling in a solid-state continuous system

TL;DR

This paper demonstrates strong optoacoustic coupling in a cavity-less waveguide system at cryogenic temperatures, enabling coherent information exchange without optical cavities, and introduces a new measurement technique for hybrid modes.

Contribution

It reports the first experimental realization of strong coupling between optical and acoustic fields in a cavity-less waveguide system using Brillouin scattering at cryogenic temperatures.

Findings

Observation of spectral splitting indicating strong coupling

Development of a novel technique to measure avoided crossing

Potential for in-line quantum signal processing

Abstract

Strongly coupling two systems allows them to exchange coherent information before the systems decohere. This important regime in light-matter interactions has predominantly been reached in optical resonator configurations. In this work, we present the experimental realization of strong coupling between optical and acoustic fields within a continuum of modes in a cavity-less configuration after a single-pass through an optical waveguide. The underlying physical effect of anti-Stokes Brillouin-Mandelstam scattering in a highly nonlinear fiber at T = 4 K allows us to experimentally demonstrate strong coupling in a waveguide scenario. We show the splitting of the optoacoustic spectral response and introduce a novel technique to measure the avoided crossing of hybrid optoacoustic modes via forced detuning. This demonstration opens a path towards in-line acoustic-waves-based quantum signal processing in waveguide systems.