Lateral, Directional, and Polarized Light Emission from a Silicon Metasurface

Silicon (Si) light sources integratable with Si waveguides are highly desirable in integrated optical circuits. Here, we investigated systematically the light emission from a Si metasurface constructed with paired Si nanocuboids under the excitation of 400 nm femtosecond laser pulses. It was revealed that such a Si metasurface supports various optical resonances in the visible-to-near-infrared spectral range. We observed the burst of hot-electron luminescence with reduced line width above a threshold of excitation irradiance. It was found that the luminescence emits mainly in the transverse direction and exhibits a dependence on the wavelength. It was shown that the blue-green light is coupled into the adjacent Si waveguide and propagates a long distance. It was confirmed that the emitted light is linearly polarized, which is independent of the polarization of the excitation laser light. Our findings pave the way for realizing Si-based lasers for integrated optical circuits.