Unit cell independent optical filter using one-dimensional photonic crystal

In this short note, we introduce an optical filter that exhibits independence from unit cells within a one-dimensional photonic crystal. Our study focuses on a one-dimensional binary Si/SiO₂ multilayer system. Utilizing the transfer matrix method, we compute transmission spectra for structures ranging from two unit cell to ten unit cells. Notably, a common transmission window is observed across all unit cells of the structure. This characteristic renders the proposed structure a viable unit cell independent optical filter in the THz frequency region.