Narrowband and high-transmissivity guided-mode resonance filter in the visible range

We introduce an approach for creating optical filters with narrow bandwidth and high transmittance within the visible light spectrum. By combining the interferometric properties of the film system and the diffraction properties of the sub-wavelength grating, we have designed a bandpass filter based with a two-dimensional subwavelength metal grating structure and an Al2O3-air bilayer coating. The Al2O3-air bilayer coating not only suppresses random scattering leakage in the short-wavelength range but also maintains the relative stability of the central wavelength position, which lead to reduced sidebands and increased transmittance of resonance peaks. Moreover, to reduce electromagnetic energy loss in the waveguide layer, we optimized the thickness of the buffer layer and introduced a bottom Al2O3 layer, enabling the filter to achieve a low full width at half-magnitude. By adjusting the grating period, the filter achieves narrow bandwidth and high transmittance resonant peaks across the entire visible spectrum. The proposed approach presents a metal grating-based guided-mode resonance transmissive filter, exhibiting a low sideband of 23%, high transmittance of 85%, a narrow bandwidth of less than 5 nm, and tunability across the entire visible light spectrum. The proposed design is experimentally validated and the results demonstrate that this method is effective in achieving excellent filtering performance in the visible spectrum.