Integrated UV/IR-cut optical filter with nanoimprinted pyramid diffuser featuring tailored light diffusion and hydrophobicity

Abstract

This study presents the design, fabrication, and characterization of a UV/IR cut optical filter integrated with a surface diffuser featuring nanoimprinted pyramid structures, aimed at achieving uniform light distribution and minimizing angular sensitivity in optical systems. The key innovation lies in the nanoimprinted pyramid diffuser, which addresses the critical limitation of angular sensitivity inherent in interference-based multilayer filters. The nanoimprinted diffuser introduces deterministic scattering properties that ensure uniform light distribution, reduce angular sensitivity, and provide stable optical performance. The multilayer filter, composed of alternating SiO₂ and TiO₂ layers, was deposited using magnetron sputtering with carefully optimized parameters to achieve high transmittance in the visible range (400–700 nm) while effectively blocking ultraviolet (200–400 nm) and near-infrared (700–1100 nm) wavelengths. The final structure consisted of 29 layers, and the measured optical performance closely matched theoretical simulations. To enhance uniform light distribution and reduce the inherent angle dependence of interference-based filters, a surface diffuser was fabricated using nanoimprint lithography, replicating randomly arranged pyramid structures etched into silicon via anisotropic KOH wet etching. By varying etch times, diffuser structures with different scattering profiles were obtained, with the 6-min etched sample exhibiting the highest haze value (92.38 %) and the strongest diffusion capability. Additionally, surface modification with F₁₃-TCS rendered the diffusers hydrophobic, with contact angles reaching a maximum of 124°, enhancing durability and self-cleaning capability. This refined approach offers a robust solution for improving optical system performance across various applications.