Achromatic prism-coupler for planar waveguide

Abstract We derive the required optical properties of a prism for coupling light achromatically into a planar waveguide. Efficient coupling over a 110 nm spectral bandwidth was experimentally demonstrated with a prism-coupler designed to match the dispersion of a particular waveguide. The design tools described here should be useful in the implementation of broadband attenuated total reflection spectroscopy in the waveguide regime to probe ultrathin and very weakly absorbing molecular submonolayers.