IR spectroscopy and preparation of nanoslits in metal thin films

Metal nanostructures allow manipulating light on a sub-wavelength length scale. We investigated the IR-optical properties of single nanosized slits in metal thin films. These nanoslits were prepared in ultrathin Au films on various substrates by applying a shadowing technique using nanowires as masks. Single nanoslits were investigated by infrared spectroscopic microscopy. The nanoslits with a width of a few hundred nanometers and a length in the 10 μm range show a transmission which increases with frequency and which exceeds the transmission of the continuous Au film in the mid-infrared range. We compare this behaviour to calculations of the small-slit transmission coefficient from classical electromagnetic scattering theory.