Terahertz near-field microscopy based on a collection mode detector

We report on the development of a collection mode near-field probe for the terahertz spectral range. The near-field detector is based on an aperture type probe with dimensions of 30×30 ${\mathrm{\mu m}}^{\mathrm{2}}.$ The collection mode technique provides higher sensitivity and higher resolution than the similar illumination mode approach. Spatial resolution better than 40 μm is demonstrated for a broad spectrum of 300–600 μm, which equals to λ/15 for the longest wavelength. The observed resolution is determined by the size of the probe aperture.