Subwavelength-scale tailoring of surface phonon polaritons by focused ion-beam implantation

Recent advances in optical nanotechnologies by controlling surface plasmon polaritons in metallic nanostructures demonstrate high potential for subwavelength-scale waveguiding of light, data storage, microscopy or biophotonics. Surprisingly, surface phonon polaritons-infrared counterparts to surface plasmon polaritons-have not been widely explored for nanophotonic applications. As they rely on the infrared or terahertz excitation of lattice vibrations in polar crystals they offer totally different material classes for nanophotonic applications, such as semiconductors and insulators. In an initial step towards nanoscale surface phonon photonics we show evidence that the local properties of surface phonon polaritons can be tailored at a subwavelength-scale by focused ion-beam modification of the crystal structure, even without significant alteration of the surface topography. Such single-step-fabricated, monolithic structures could be used for controlling electromagnetic energy transport by surface phonon polaritons in miniaturized integrated devices operating at infrared or terahertz frequencies. We verify the polaritonic properties of an ion-beam-patterned SiC surface by infrared near-field microscopy. The near-field images also demonstrate nanometre-scale resolved infrared mapping of crystal quality useful in semiconductor processing or crystal growth.