Two‐Tier Nanolaminate Plasmonic Crystals for Broadband Multiresonant Light Concentration with Spatial Mode Overlap

Abstract

AbstractEffective trapping and nanolocalization of different colored photons simultaneously at the same position remain a challenge in nanophotonics research but can boost applications based on nonlinear multiphoton processes. For achieving broadband nanoscale light concentration, a promising strategy is to employ multiresonant plasmonic devices that support multiple hybridized surface plasmon modes with spatial overlap at several different resonance wavelengths. However, high‐order plasmonic modes from hybridization tend to have a dark multipolar nature and are less useful due to weak interactions with free‐space light. Here, it is reported that nanolaminate plasmonic crystals in a two‐tier configuration can support many (≈10) spatially overlapped and highly‐excitable hybridized plasmonic modes under free‐space light illumination between 400 and 1400 nm. Combination of nanoimprinting lithography and multilayered physical vapor deposition techniques enables wafer‐scale fabrication of nanolaminate plasmonic crystals consisting of nanolaminate nanodome and nanohole arrays as the two closely‐separated subsystems, and measurements demonstrate their multiresonant plasmonic responses in good agreement with numerical calculations. Coupled‐mode theory analysis reveals that the unique broadband multiresonant responses of the two‐tier nanolaminate plasmonic crystals are due to the synergistic effects of the strong near‐field interactions between the modes in the nanodome and nanohole subsystems and the ground‐plane‐like loading effect from the nanohole subsystem.