Stacked subwavelength grating with high transmission

Abstract

We propose a stacked subwavelength grating scheme generated multi-mode coupling that is continuously tunable in the visible range with high transmittance. This scheme uses BK7 glass as the substrate, onto which a layer of polydimethylsiloxane (PDMS) thin film is added. Each layer of the stacked grating is composed of different materials, from top to bottom are Ag-MgF2-BK7-Ag. By coupling different propagation modes generated by different grating layers, various transmission spectra throughout the entire visible range can be achieved. This scheme can not only allow the tuning range of the resonant peak cover the entire visible, but also bring extremely high transmittance, accompanied by sidebands below 10%, and the maximum peak transmittance can exceed 98%. Based on the mode matching method, this article has analyzed the magnetic field distribution in the entire structure space and the diffraction efficiency of all levels of diffraction waves. Our findings have potential applications in multispectral image sensors.