A metal-dielectric antenna for terahertz near-field imaging

We present an antenna-based approach to near-field imaging and spectroscopy, which can be used for both continuous-wave and pulsed broadband electromagnetic radiations from microwave to terahertz frequencies. Our near-field antenna consists. of a rectangular-shaped block of low-loss dielectric material sharpened to a pyramidal tip which is partially metallized and terminated by a micron-sized plane facet. At this facet the entire energy of the incident wave is concentrated as a very high but strongly localized electric held, which can be used as a sensitive near-field microprobe for electromagnetic radiation. Currently, experiments in reflection geometry with pulsed terahertz radiation and continuous-wave radiation near 80 GHz reveal a frequency-independent spatial resolution of about 20 Am corresponding to lambda/200 at 80 GHz, which is only limited by the size of the facet terminating the tip. (c) 2005 American Institute of Physics.