High-resolution violet-band silicon metasurface spectrometers via tailoring the spatial localization of electromagnetic fields

Computational spectrometers based on metasurfaces offer fast speeds and a compact volume, making them particularly suitable for portable applications. However, the permittivity of silicon has a large imaginary part in the violet band, deteriorating the performance of silicon computational spectrometers. Here, we propose metasurface spectrometers composed of an array of silicon nanostructures with a titanium dioxide (TiO 2 ) film sitting on a silica substrate. By tailoring the spatial localization of the electromagnetic field within the (TiO 2 ) film, the system shows negligible absorption in the violet band, achieving high Q-factors in the hundreds, thereby realizing a spectrometer with a high-spectral resolution of approximately 2 nm in the violet band. Our method offers insights into the design of high-spectral resolution metasurface spectrometers.