Polarizing color filter based on a subwavelength metal-dielectric grating

We propose a polarizing color filter based on a one-dimensional subwavelength metal-dielectric grating combining the functions of a polarizer and a color filter. The proposed device consists of three parts: a substrate, a dielectric grating, and a metal grating. The effects of the dielectric grating and the metal grating are investigated in detail by rigorous coupled-wave analysis. Performance is enhanced effectively by utilizing a dielectric grating of high equivalent refractive index. Typical optimized structural parameters are obtained, in which more than 72.6% broadband transmission with >21 dB polarization extinction ratio are simultaneously achieved for a tricolor filter. For transverse electric (TE) polarized light, its reflection efficiency is more than 71.8% in the broad passband light range, which can be recycled by rotating the TE polarization in part into transverse magnetic polarization and reimpinging on the designed device to increase the total energy efficiency. Numerical results show that peak transmission efficiency (PTE) is increased by at least 12.9% using recycled TE-polarized light.