An apparatus for analyzing, identifying or imaging an target including a
source of pulsed signals in the range of frequencies from 100 GHz to over
2 THz focused on or transmitted through the target; and a detector for
acquiring spectral information from signals reflected from the target and
using a multi-spectral heterodyning process to generate an electrical
signal representative of some characteristics of the target. The source
of pulse signals and the detector are photoconductive switches activated
by a pulsed laser beam from a single mode-locked laser.