Polarization dependent, plasmon-enhanced infrared transmission through gold nanoslits on monolayer black phosphorus

Enhanced transmission is essential in many application cases. However, as an ordinary method to enhance wave transmission, traditional extraordinary transmission based on nanohole array structures has no capability to widen its operation bandwidth. Here, we use a continuous monolayer black phosphorus film to enhance transmission through gold nanostructure arrays at the mid-infrared region. By exciting surface plasmon polaritons at the BP/gold nanostructure arrays interface, enhanced transmission over a broad range of wavelengths was theoretically demonstrated. Using finite-difference time-domain simulations, we analyzed the effects of geometric parameters on the transmission spectra and demonstrated unique polarization-dependent transmission enhancement in BP/gold silt arrays and BP/gold patch arrays, which originates from the anisotropic properties of BP. Our work provides new guidance to the design of broadband, polarization-dependent extraordinary transmission enhancement.