Ultra-Narrowband High-Transmissivity Guided-Mode Resonance Filter Based on Dual Dielectric Film Structure and High Refractive Index Waveguide Layer

In this study, we propose a novel approach to achieve an ultra-narrow bandwidth and high transmittance filter in the visible range. By employing TiO
₂
as the waveguide layer material, the coupling energy in the waveguide layer is enhanced, leading to a reduction in the full width half maximum (FWHM). Additionally, a double-layer dielectric film structure composed of SiO
₂
and Al
₂
O
₃
is employed on the Ag grating to suppress random scattering leakage in the short wavelength range, resulting in reduced sidebands and improved transmittance of the resonant peak. To minimize wave loss between the metal grating and the waveguide layer, a SiO
₂
dielectric layer is introduced. By adjusting the metal grating period, the resonance peak position can be shifted across the entire visible range. The proposed approach offers a metal grating-based guided-mode resonance (GMR) transmissive filter with low sidebands, high transmittance, ultra-narrow bandwidth, and tunability in the entire visible range. Experimental validation of the proposed design is conducted, and the results demonstrate the effectiveness of this approach in achieving superior filter performance in the visible spectral range.