Transmission resonances through aperiodic arrays of subwavelength apertures

Shining through A Nature paper in 1998 reported the transmission of resonantly enhanced light through 'plasmonic lattices', which are metal films punctured with arrays of holes smaller than the wavelength of the light. The phenomenon generated significant interest, first as it was a surprise, and second because it has potential applications in near-field optical microscopy, photolithography, displays and elsewhere. The periodicity of the holes was thought crucial, but new experiments show that this is not so. Though randomly distributed holes arrays with quasicrystal or approximate quasicrystal structure do. As an added bonus, transmission resonances for the lattices used in this experiment are in the terahertz range, for which there is a shortage of optoelectronic materials. In contrast to the conventional view, this paper reports transmission resonances in the terahertz frequency range for aperiodic aperture arrays, with quasicrystal or approximate quasicrystal structure. Resonantly enhanced light transmission through periodic subwavelength aperture arrays perforated in metallic films 1 has generated significant interest because of potential applications in near-field microscopy, photolithography, displays, and thermal emission 2 . The enhanced transmission was originally explained by a mechanism where surface plasmon polaritons (collective electronic excitations in the metal surface) mediate light transmission through the grating 1 , 3 . In this picture, structural periodicity is perceived to be crucial in forming the transmission resonances. Here we demonstrate experimentally that, in contrast to the conventional view, sharp transmission resonances can be obtained from aperiodic aperture arrays. Terahertz transmission resonances are observed from several arrays in metallic films that exhibit unusual local n -fold rotational symmetries, where n = 10, 12, 18, 40 and 120. This is accomplished by using quasicrystals with long-range order, as well as a new type of ‘quasicrystal approximates’ in which the long-range order is somewhat relaxed. We find that strong transmission resonances also form in these aperiodic structures, at frequencies that closely match the discrete Fourier transform vectors in the aperture array structure factor. The shape of these resonances arises from Fano interference 4 of the discrete resonances and the non-resonant transmission band continuum related to the individual holes 5 . Our approach expands potential design parameters fo