Characterization of Terahertz Beam Profile and Propagation

Two techniques for imaging a terahertz (THz) beam profile are described and employed in characterizing the THz beam propagation in a time-domain spectrometer. Aperture scanning yields a 2-D cross-sectional map of field amplitude at selected frequencies that is used to track beam evolution along its path. The Hartmann test produces a 2-D topographical image of the wavefront, also at selected frequencies. The results are compared with theory, and the respective advantages of the two methods are discussed.