Analysis and optimization of a focusing metal-dielectric probe for Near-field Terahertz Imaging

Illumination techniques play an important role in
millimeter and Terahertz wave imaging. In aperture near-field
imaging, the resolution depends on the size of the aperture; in
aperture-less scattering near-field imaging, the resolution
depends on the tip-sample distance and the size of the scatter.
Normally, sharp metal tips acts as an antenna and illuminated by
a focusing beam, it is impossible to focus only on the tip of the
metal needle, the propagation along the shaft of the needle
impacts analyzing the received signal. A combination of an
aperture and aperture-less near-field illumination technique is
presented in this paper. We use the focusing beam coming out
from the aperture probe as a near field illumination source which
just covers the sharp end of the aperture-less metal tip to
decrease the stray wave. A focusing metal-dielectric tapered
probe is analyzed, the material of the dielectric part is discussed
and lower permittivity materials are used instead of highly
resistive silicon or sapphire, the geometric dimension
optimizations are simulated in Microwave studio of CST

Publication year:2013

Keywords:focusing, metal-dielectric probe, near-field