Beam propagation effects in THz time-domain tomography

We have performed 2-dimensional tomographic measurements upon shaped phantoms constructed from material with low optical power, using a time-domain THz arrangement. While the phantom morphology can be successfully reconstructed using the time-delay data, use of the THz pulse amplitude is less reliable, demonstrating distortions that may be a consequence of beam diffraction effect. This effectively masks the true attenuation contrast of the object.