One-mode model for patterned metal layers inside integrated color pixels

Optimized design of the optical filters inside integrated color pixels (ICPs) for complementary metal-oxide semiconductor image sensors requires analytical models. ICP optical filters consist of subwavelength patterned metal layers. We show that a one-mode model, in which subwavelength gaps in the metal layer are described in terms of single-mode waveguides, suffices to predict the salient features of measured ICP wavelength selectivity. The Airy-like transmittance formula, derived for transverse-electric polarization, predicts an angle-independent cutoff wavelength, which is in good agreement with predictions made with a two-dimensional finite-difference time-domain method.