Photonic crystal-based smart window design for seasonal solar energy management in Beni-Suef City, Egypt

This paper presents a broadband optical short-wave pass (OSWP) multilayer filter optimized for smart-window integration to enhance building energy efficiency in Beni-Suef, Egypt. The structure comprises CaF 2 , Si 3 N 4 , and ZnS dielectric stacks in a dual-laminate configuration designed using the transfer matrix method (TMM). The optimized design achieves high visible transmittance (∼86% at 400–700 nm) while strongly suppressing near-infrared (NIR) radiation across 800–1500 nm. A well-defined photonic band gap (PBG) is confirmed through spectral and phase analyses, showing strong angular sensitivity. With increasing incidence angle, the PBG exhibits an ∼100nm blue shift, enabling passive seasonal modulation of solar heat: effective NIR blocking for summer cooling and enhanced NIR transmission for winter heating. Compared with conventional low-E glazing and previously reported photonic crystal filters, the proposed smart-window design offers superior spectral selectivity and climate-responsive performance without electrical power or active control. These results highlight a practical passive solution for reducing energy demand in buildings located in hot-arid regions.