A simplified guided-mode-resonant wavelength filter with ultra-low aspect ratio for polarization-insensitive performance at 45-degree incidence

We propose a polarization-insensitive guided-mode-resonant wavelength filter designed for 45-degree incidence. Unlike conventional dielectric multilayer filters which require dozens or even hundreds of layers and exhibit strong polarization dependence at large angle of incidence, our design uses a single-layer coating and an ultralow-aspect-ratio structure. This structure operates efficiently at a 45-degree angle and exhibits low polarization dependence. This simplified geometry has the potential to be manufactured on a large scale using techniques such as nanoimprint lithography or injection molding. This approach enables the production of compact optical filters suitable for integrated photonic modules, including those used in wavelength-division multiplexing systems.