Very high resolution near-field chemical imaging using an infrared free electron laser

High resolution infrared Imaging of thin films and biological systems is one of the most challenging experimental problems in contemporary science and technology. In this work, we have for the first time successfully tested a novel high resolution approach, based on a spectroscopic version of scanning near-field optical microscopy (SNOM). The coupling of the Vanderbilt Free Electron Laser tunable infrared radiation to SNOM apparatus enabled us to clearly reveal different chemical constituents on a growth medium for biofilm. The images were obtained by SNOM detection of reflected 6.95 µm photons, corresponding to the stretch absorption of sulfur and nitrogen compounds, constituents of the growth medium. We attained a lateral resolution of 0.2 mm (l/35), well below the diffraction limit of classical microscopy.