Fabrication and characterization of three-dimensional copper metallodielectric photonic crystals

Three-dimensional metallodielectric photonic crystals were created by fabricating a micron-scale polymeric template using multi-photon direct laser writing (DLW) in SU-8 and conformally and selectively coating the template with copper (Cu) via nanoparticle-nucleated electroless metallization. This process deposits a uniform metal coating, even deep within a lattice, because it is not directional like sputter-coating or evaporative deposition. Infrared reflectance spectra show that upon metallization the optical behavior transitions fully from a dielectric photonic crystal to that of a metal photonic crystal (MPC). After depositing 50 nm of Cu, the MPCs exhibit a strong plasmonic stop band having reflectance greater than 80% across the measured part of the band and reaching as high as 95% at some wavelengths. Numerical simulations match remarkably well with the experimental data and predict all dominant features observed in the reflectance measurements, showing that the MPCs are structurally well formed. These data show that the Cu-based process can be used to create high performance MPCs and devices that are difficult or impossible to fabricate by other means.