Scanning Near-field Optical Microscopy

Scanning near-field optical microscopy (SNOM) allows one to realise optical imaging of surface structures with spatial resolutions on the nanometer scale, i.e., beyond the classical diffraction limit. Imaging in SNOM is based on the detection of near-field, or non-propagating, field components with an optical probe scanned close to the inspected sample surface. This is a new but already recognised and widely used technique. It represents an optical member of the family of scanning probe microscopies, which also includes well known scanning tunneling (STM) and atomic force (AFM) microscopies.
A reflection SNOM arrangement has been set up and investigated in collaboration with DME - Danish Micro Engineering A/S. Imaging characteristics of the microscope and underlying principles of image formation have been experimentally studied and theoretically analyzed. High resolution (~50 nm) polarization- and wavelength-resolved imaging of different samples, e.g. single quantum wells, has been demonstrated. Polarization sensitivity better than 10-3 has been achieved in near-field imaging. Future research activities involve application of this technique for near-field imaging of surface anisotropy and its extension in the domain of nonlinear optics.