Nanometer scale light focusing with high cavity-enhanced output
J. Appl. Phys.
Efficient nanoscale optical focusing is demonstrated in double-structured thin metallic films supporting both surface plasmons and cavity eigenmodes. Numerical simulations show that efficient mode coupling can dramatically enhance the transmission of a subwavelength slit. For a spot size of ~/10, the cavity induced enhancement is about an order of magnitude, leading to a final structure output (transmitted power/incident power) of ~30%. Results are discussed in terms of cavity-slit mode matching and photon trapping within the cavity.