Subwavelength Metal Hole Array Surface Plasmon Enhanced Transmission Phenomenon

Resonantly enhanced transmission through metallic nanoaperture arrays has received much attention since the phenomenon of Extraordinary Optical Transmission (EOT) was discovered by Ebbesen in 1998.It opened up a new prospect for nanoscale manipulation of light and found an increasing number of applications in optoelectronic technologies as well as sensors. It is a hot topic at present and the arguments still continue. For effective application of this EOT phenomenon, it is of great importance to find the underlying physical mechanism. In this work, we will study enhanced transmission through various nanoaperture arrays.We made use of the focused ion beam (FIB) technique to fabricate various planar crystals in thin gold films. Transmission spectra of these crystals are observed with strong dependence on the nanoaperture's arrangement and the hole spacing, indicating that the resonances result from the effect of horizontal surface plasmon (SP) on both metal-air and metal-glass interfaces. We elucidate the mechanisms of the transmission resonances and the relationship between these resonances and the structure factors. We also compare the enhanced transmission effects of one kind of crystal with those of the other kinds. Of all kinds of crystals, only the quasicrystal exhibits broadband plasmonic resonances, the explanation of which is that the multiple SP modes excited in the quasicrystal give rise to the enhanced transmission in a wide range of wavelength. Near-field scanning optical microscope images provide direct evidence for surface plasmon-mediated enhanced transmission in a wide range of wavelength through the quasicrystal.These characteristics are much desired in practical applications for broadband plasmonic devices.Since FIB system is unsuitable for fabricating nanoaperture structures in a large area, which restricts the studies and applications of the enhance transmission through metallic nanoaperture arrays, we set up a laser interference lithography (LIL) system based on Lloyd plane mirror. This method is simple, fast, and available for fabricating nanoaperture structures in a large area. Therefore, LIL system will be an important process method to fabricate metallic nanoaperture arrays.