Focusing of surface phonon polaritons

Surface phonon polaritons (SPs) on crystal substrates have applications in microscopy, biosensing, and photonics. Here, we demonstrate focusing of SPs on a silicon carbide (SiC) crystal. A simple metal-film element is fabricated on the SiC sample in order to focus the surface waves. Pseudoheterodyne scanning near-field infrared microscopy is used to obtain amplitude and phase maps of the local fields verifying the enhanced amplitude in the focus. Simulations of this system are presented, based on a modified Huygens' principle, which show good agreement with the experimental results. (C) 2008 American Institute of Physics.