Plasmonic infrared bandstop reflective filter

Various types of free-space plasmonic bandstop filters are reviewed. The plasmonic multilayer structure shows multiple localized surface plasmon (LSP) resonance modes with extraordinary high angle tolerance. Through modifying the plasmonic multilayer structure to a plasmonic T-shaped array, the multiple LSP modes can be suppressed. The filtering properties present a single resonance dip with a low sideband. Through modifying the plasmonic T-shaped array to be an asymmetric one, dual resonance modes can be easily designed. Finally, a nanoporous Au film is proposed to act as a bandstop filter. The fabrication processes are simple and the resonance dip can be manipulated by altering the annealing temperature.