Topological optical and phononic interface mode by simultaneous band\n inversion

Abstract

Interface modes have been widely explored in the field of electronics,\noptics, acoustics and nanophononics. One strategy to generate them is band\ninversion in one-dimensional superlattices. Most realizations of this type of\ntopological states have so far been explored for a single kind of excitation.\nDespite its potential in the manipulation and engineering of interactions,\nplatforms for the simultaneous topological confinement of multiple excitations\nremain an open challenge. GaAs/AlAs heterostructures exhibit enhanced\noptomechanical interactions due to the intrinsic colocalization of light and\nsound. In this work, we designed, fabricated, and experimentally studied a\nmultilayered structure based on GaAs/AlAs. Due to the simultaneously inverted\nband structures for light and phonons, colocalized interface modes for both\n1.34 eV photons and 18 GHz phonons appear. We experimentally validated the\nconcept by optical reflectivity and coherent phonon generation and detection.\nFurthermore, we theoretically analyzed the performance of different topological\ndesigns presenting colocalized states in time-domain Brillouin scattering and\ndeduce engineering rules. Potential future applications include the engineering\nof robust optomechanical resonators, compatible with the incorporation of\nactive media such as quantum wells and quantum dots.\n