1. A system for performing terahertz (THz) wave diffraction tomography, the system comprising: a. an optical probe beam path and a pulsed optical probe beam generator; b. a THz beam path and a pulsed THz radiation beam generator; c. a two-dimensional THz radiation sensor; d. a sample holding area; e. a two-dimensional optical sensor; and f. means for converging both the THz path and the optical beam path onto the THz sensor, wherein: the optical probe beam generator generates an expanded collimated optical probe beam traveling along the optical probe beam path; the THz beam generator generates an expanded and collimated THz beam traveling along the THz beam path; the sample holding area is in the THz beam path and is adapted to permit changing an orientation of a sample placed therein relative to the THz beam; the two-dimensional THz radiation sensor has an area A s and is positioned along the THz beam path at a distance from the sample such that area A s intercepts all THz radiation emerging from the sample along the THz path within a divergence angle of about 12 degrees or more; and the expanded optical probe beam has a cross section larger than a cross section of the THz beam incident on the THz sensor and the optical sensor is positioned along the optical beam path and has an area larger than the cross section of the expanded optical probe beam.