Influence of structural parameters to polarization-independent color-filter behavior in ultrathin Ag films

Very recently, the subtractive color filters with transmission efficiencies of 60~70% at visible wavelengths, observed in ultrathin (30 nm-thick) Ag film with one dimensional (1D) nanogratings, have been reported, which fundamentally differ from existing additive color filters. However, subtractive color filters with ultrathin 1D Ag nanogratings are strongly dependent on the polarization of light source, which might be undesirable for many applications. In this work, we present polarization-independent subtractive color filters of Ag films with various two-dimensional nanohole arrays. The dependences of color filter properties on film thickness, hole array period and the ratio of hole diameter to period were systematically studied. We found that color filter properties strongly correlate with film thickness and hole array period, and are insensitive to the ratio of hole diameter to period studied here. Possible mechanisms are discussed.