Optical and structural properties of metal-dielectric photonic band gap structures

We designed a series of metallo-dielectric multilayers transparent in visible-wavelength range using dielectric materials with high, medium, and low refractive indexes, for a systematic investigation on the coupling between resonators. However, the transparent metal systems fabricated using sputtering method failed to reach the designed maximum transmission levels. Non-destructive depth profiling of metallo-dielectric multilayers revealed that structural imperfection, such as surface roughness and interface layers, were responsible for the observed discrepancy in the maximum transmission level. Respective substitutions of ZnS-SiO2 and APC (an alloy of Ag, Palladium, and Copper), which are the materials that tend to grow with less roughness, for ZnS and Ag resulted in a significant improvement in the maximum transmission level.