A novel near-field terahertz imaging probe for biological imaging

We report a resonant frequency-domain terahertz (THz) near-field probe setup and its application in imaging a slice of a mouse brain slice and the leaf of a dwarf umbrella tree. In our probe setup, we coupled the waveguide output of a terahertz Vector Network Analyzer (VNA) system to feed a horn antenna and then used the horn antenna to excite a sharp iron or Teflon tip. The tip transforms and concentrates the Transverse Electric (TE) mode waves of the horn to longitudinal electric fields (LE) at the metallic or Teflon tip for stronger interaction with a sample. The spatial resolution of the probe setup (from spread with an iron and a Teflon tip function measurements) were 445 μm (at 0.8375 THz) and 230 μm (at 1.0422 THz), respectively.