title: Quasi-cylindrical wave contribution in experiments on extraordinary optical transmission.
abstract: A metal film perforated by a regular array of subwavelength holes shows unexpectedly large transmission at particular wavelengths, a phenomenon known as the extraordinary optical transmission (EOT) of metal hole arrays. EOT was first attributed to surface plasmon polaritons, stimulating a renewed interest in plasmonics and metallic surfaces with subwavelength features. Experiments soon revealed that the field diffracted at a hole or slit is not a surface plasmon polariton mode alone. Further theoretical analysis predicted that the extra contribution, from quasi-cylindrical waves, also affects EOT. Here we report the experimental demonstration of the relative importance of surface plasmon polaritons and quasi-cylindrical waves in EOT by considering hole arrays of different hole densities. From the measured transmission spectra, we determine microscopic scattering parameters which allow us to show that quasi-cylindrical waves affect EOT only for high densities, when the hole spacing is roughly one wavelength. Apart from providing a deeper understanding of EOT, the determination of microscopic scattering parameters from the measurement of macroscopic optical properties paves the way to novel design strategies.
authors.affiliation: Leiden University, Huygens Laboratory, PO Box 9504, 2300 RA Leiden, The Netherlands. beijnum@physics.leidenuniv.nl
authors.forename: Frerik
authors.initials: F
authors.lastname: van Beijnum
authors.forename: Chris
authors.initials: C
authors.lastname: Rétif
authors.forename: Chris B
authors.initials: CB
authors.lastname: Smiet
authors.forename: Haitao
authors.initials: H
authors.lastname: Liu
authors.forename: Philippe
authors.initials: P
authors.lastname: Lalanne
authors.forename: Martin P
authors.initials: MP
authors.lastname: van Exter