Loss Control with Annealing and Lattice Kerker Effect in Silicon Metasurfaces

Abstract

The resonant phenomena of metasurfaces highly depend on the scattering strength of each component and their interferences. The losses modify the phase and reduce the amplitude of all multipoles; thus, the loss control is vital for obtaining the designed properties. Amorphous (a-)Si has a higher absorption coefficient than that of the crystalline form, which limits its optical application. A simple rapid thermal annealing (RTA) path to refine the a-Si metasurfaces is found. It is applied to the sputtering-made a-Si metasurface comprising square array of nanodisks. While the large loss smears out the resonances for the as-made metasurface, the sharp and near-zero reflectance with near-perfect absorptance is achieved after RTA, satisfying the lattice Kerker condition via the interference of magnetic and electric dipoles. At the lattice Kerker condition, the forward-enhanced and backward-reduced directional photoluminescence is observed from the emitter layer deposited on the metasurface. The numerical results are all found to be in good agreement with the experimental results, and the multipole expansion analysis for the single nanodisk gives the physical background of this observation. This refinement of a-Si metasurfaces by RTA treatment paves the simple and robust way for realizing thrilling optical and optoelectrical applications, such as detectors and filters.