Enhancing Brillouin Scattering with Chalcogenide Metasurfaces of Optical Bound States in the Continuum and Mechanical Resonances

Abstract Brillouin scattering provides a unique approach in diverse applications ranging from sensing to signal processing and beyond. The recent advancement in Brillouin scattering research has been driven by the development of integrated photonic platforms. However, the realization of efficient Brillouin scattering with substantial gains at low pump powers within compact devices is still a challenge. Here, a chalcogenide metasurface is proposed and demonstrated as a promising candidate for facilitating spontaneous Brillouin scattering. By employing Ge 25 Sb 10 S 65 materials with remarkable photoelastic properties and leveraging the capacity of metasurfaces to effectively confine light waves through quasi‐bound states in the continuum, alongside their ability to confine acoustic waves via mechanical resonances, a substantial Brillouin gain of up to 27.7 dB at a low pump power of 23 mW is achieved within a metasurface with a compact dimension of <0.03 cm. The superior performance of chalcogenide metasurfaces‐based Brillouin scattering may hold profound potential to advance Brillouin scattering research and find wide applications.