Abstract: A method for imaging a sample, the method comprising the steps of: (a) irradiating the surface of a sample with a source of coherent substantially continuous radiation with a frequency in the range 25 GHz to 100 THz; (b) detecting said radiation reflected from or transmitted by the sample; (c) providing and detecting a probe beam having a phase related to that of the radiation leaving the source; (d) analysing the detected radiation for at least one characteristic feature within the radiation and monitoring any change in phase of such at least one feature in order to derive structural information about the sample as a function of depth from the surface of the sample.

Abstract: Apparatus and method for detecting an explosive material, involving irradiating an object with a continuous wave (CW) or pulsed beam of Terahertz radiation, preferably in the frequency range of 100 GHz to 100 THz and detecting radiation transmitted and/or reflected from the object. A spectrum is constructed from the detected radiation, which is indicative of a fundamental property of the explosive material. This constructed spectrum is compared with one or more known spectra of explosive materials to determine whether a likeness exists.

Abstract: An antenna comprising a photoconductive material (61) and a plurality of spaced apart electrodes (69, 71) provided on said photoconductive material (61), each electrode (69, 71) having at least one facing edge which faces a facing edge of an adjacent electrode, a physical barrier (67) being provided abutting a facing edge of at least one electrode (69, 71), said barrier (67) extending to at least the full height of said facing edge.

Abstract: A semiconductor material with photoconductive properties and a method of the semiconductor, wherein a base material is grown and then annealed post-growth at a temperature of 475° C. or less. It has been found that be annealing at temperatures of 475° C., or less the carrier lifetime of the material and the resistivity can be optimized so as to obtain semiconductor with useful photoconductive properties.