Competence Center for Micro- and Nanotechnologies

Contrary to thick opaque metal films, where an extraordinary high transmission of light is observed through subwavelength hole arrays, in ultrathin metal films perforation can lead to a suppressed or an enhanced transmission. Here we systematically investigate the optical transmission through semitransparent Au films structured with square arrays of subwavelength holes experimentally and theoretically. We measure the transmission at various angles of incidence through hole arrays with different thicknesses, diameters, and periodicities. We compare the data with an empty lattice approximation and with calculations based on a Fourier modal method. The results evidence that for gold the exact dielectric function has to be considered and that not only the periodicity and film thickness influences the transmission, but that also the shape and diameter of the holes play an important role.