High angular tolerant color filter using subwavelength grating

A reflective color filter based on a two-dimensional subwavelength grating is proposed. The filter has been designed by performing numerical simulations and has been fabricated on 5×5 mm2 quartz glass using electron beam lithography. The grating color filter shows reflectance of 74% and spectral width of about 80 nm. Furthermore, it has good angular tolerance, up to ±45°, for unpolarized incident light. By analyzing the reflectance spectral distributions in the band diagram, we found that high angular tolerance is achieved due to the high refractive index contrast of grating structures.