Topological optical and phononic interface mode by simultaneous band inversion

TL;DR

This paper demonstrates the design and experimental validation of a multilayered GaAs/AlAs structure that hosts simultaneously inverted topological band structures for light and phonons, enabling colocalized interface modes for both excitations.

Contribution

It introduces a novel platform for simultaneous topological confinement of optical and phononic modes in a multilayered heterostructure, with experimental validation and theoretical analysis.

Findings

Colocalized interface modes for photons and phonons observed

Experimental validation via optical reflectivity and phonon detection

Design rules for topological multimode confinement deduced

Abstract

Interface modes have been widely explored in the field of electronics, optics, acoustics and nanophononics. One strategy to generate them is band inversion in one-dimensional superlattices. Most realizations of this type of topological states have so far been explored for a single kind of excitation. Despite its potential in the manipulation and engineering of interactions, platforms for the simultaneous topological confinement of multiple excitations remain an open challenge. GaAs/AlAs heterostructures exhibit enhanced optomechanical interactions due to the intrinsic colocalization of light and sound. In this work, we designed, fabricated, and experimentally studied a multilayered structure based on GaAs/AlAs. Due to the simultaneously inverted band structures for light and phonons, colocalized interface modes for both 1.34 eV photons and 18 GHz phonons appear. We experimentally validated the concept by optical reflectivity and coherent phonon generation and detection. Furthermore, we theoretically analyzed the performance of different topological designs presenting colocalized states in time-domain Brillouin scattering and deduce engineering rules. Potential future applications include the engineering of robust optomechanical resonators, compatible with the incorporation of active media such as quantum wells and quantum dots.