Extraordinary Transmission through Subwavelength Apertures

Abstract

Previous chapters discussed the excitation and propagation of SPPs along a planar interface and the scattering and damping of LSPRs around a spatial particle. This chapter discusses the transmission phenomena of electromagnetic energy passing through narrow holes. Light passing through subwavelength holes in opaque metallic films has fascinated specialists for over a century due to the fundamental concerns in both optical science and applications. There are numerous significant works investigating either single holes or hole arrays. The early theoretical contributions date back to Lord Rayleigh’s interpretation of the diffraction effect in metal gratings.1 Most works focused on the strong transmission for light with wavelengths longer than the array periodicity. The peculiar phenomena of extraordinary optical transmission (EOT) were first observed experimentally in aperture arrays that penetrate metallic films. In those experiments, the diameters of metallic holes were much smaller than the wavelengths. EOT findings have motivated research of the transmission properties of single holes, hole arrays, and various shapes of holes. The increased interest is concerned with the transmission properties of metallic nanostructures, although the mechanisms of EOT are a matter of debate. Over the last few decades, various types of aperture structures have been investigated, as shown in Fig. 4.1. Optical transmission has been expanded from a single aperture with diverse geometries to apertures surrounded by periodic structures. Various types of aperture structures provide a multitude of optical properties, especially transmission efficiency and local field enhancements. These properties have been achieved at arbitrary resonant wavelengths of interest ranging from visible light to terahertz, even the acoustic wave.