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.
As the demand for ultrahigh density information storage continues to grow, recording mark size of several tens nanometer which is smaller than the optical diffraction limit is required in optical memory. Functional film super-resolution technique is one of practical approaches to overcome the optical diffraction limit. Optical constants are important parameters to optical films as super-resolution masks. In this paper, the influence of film thickness on optical constants of antimony-based bismuth-doped super-resolution mask layer is investigated. The structure of the samples with different thickness was studied by X-ray diffraction. The transmission spectrum was measured by spectrophotometry. The optical constants of the films in the range of 300-800 nm were measured by spectroscopic ellipsometry. The results show that the structure of the film transforms from amorphous state to crystal state when the thickness increases from 7 nm to 300 nm. In the range of 300-800 nm, the refractive index and extinction coefficient increase with increasing wavelength. The transmission decreases rapidly when the thickness increases from 7 nm to 30 nm. The influences of film thickness on optical constants are more significant in the thickness range of 7-50 nm than that in the thickness above 50 nm.
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