THz near-field optics and microscopy

                 Paul Planken
         Faculty of Applied Sciences
        University of Technology Delft

In ordinary THz imaging, the spatial resolution is typically limited to
about a wavelength, corresponding to values of around 300 microns. This
spatial resolution is clearly insufficient to image microscopic objects.
We present results on a new method to improve the spatial resolution in
THz imaging, base on using a sharp metal tip as a sub-wavelength-sized
source of THz radiation. By uniquely measuring the near-field in the
neighbourhood of this metal tip, we can image microscopic objects. In
addition, we find that the technique provides information on the
properties of the near-field of metal tips, which may have consequences
for near-field measurements in the visible and near-IR.