Mid-infrared scanning near-field optical microscope resolves 30 nm

We explore the performance of a scanning near-field infrared microscope, wh ich works by scattering tightly focused CO2 laser radiation (lambda = 10 mu m) from the apex of a metallized atomic force microscope tip. The infrared images of test samples prove a spatial resolution of 30 nm and are free of topographical and inertial artefacts, thus they should be of great interes t for practical applications. We also observe that the infrared contrast va nishes when the input beam polarization is orthogonal to the tip axis, in a ccordance with theoretical expectations for a mechanism of longitudinal fie ld interaction.