Prism coupled Terahertz waveguide sensor

A simple THz waveguide element has been used as a sensitive sensor for adsorbates on surfaces. The evanescent wave from total internal reflection off a silicon prism was used to couple pulsed THz radiation frequency selectively into the waveguide. The coupled frequencies were determined via time domain spectroscopy and react sensitively to any changes of thickness or phase shift upon reflection. In particular, the sensitivity to phase shifts makes this waveguide sensor attractive for the detection of very thin adsorbates. Typical sensitivity and reliability limits for the detection of adsorbates are discussed. (c) 2005 American Institute of Physics.