Angle-tolerant polarization-tuned color filter exploiting a nanostructured cavity.

A polarization-mediated color filter featuring a high angular tolerance is proposed incorporating a metal-dielectric-metal etalon based on a nanostructured cavity, where a one-dimensional subwavelength grating of a high refractive index is embedded in a base layer of a low refractive index. The aim of the nanostructured cavity is mimicking of the equivalent birefringent medium whereby different effective refractive indices are exhibited depending on the incident polarization. As the transmission peak of the etalon is effectively tuned through the tailoring of the refractive index of the cavity, the proposed filter is capable of providing a continuum of vivid output colors through a dynamic control of the polarization. The effective medium theory is chiefly applied for an investigation of the birefringent characteristics of the nanostructured cavity. A dielectric overlay that acts as an anti-reflection coating is specifically adopted for the etalon to enhance the transmission efficiency. The proposed polarization-tuned filter evidently provides a high transmission of ~71% and a high angular tolerance of ~35° in conjunction with a wide polarization-mediated color tuning.