Optical Transmission of Evanescent Modes through Dielectric-filled Subwavelength Apertures
Huizhong Xu, St. John’s College of Liberal Arts and Sciences, Department of Physics
Abstract: Previous studies have shown that extraordinary transmission through a dielectric-filled subwavelength aperture can be obtained if the dielectric constants of the cladding metal and aperture filling are matched. However, a perfect dielectric constant matching is hard to achieve in practice resulting in a cutoff region beyond which only evanescent modes exist. We show that for a particular choice of substrate and exit materials covering the aperture, extraordinary transmission of evanescent modes through subswavelength apertures can still be obtained due to the resonant excitation of surface plasmons at both ends of the waveguide. This is demonstrated by simulating the transmission of 488 nm light incident on a 40-nm-diameter aperture filled with ZnO in a 100-nm-thick silver film, for which transmission of more than 40% is obtained when glass and water are chosen as the substrate and exit media respectively.