(EN) A Thz investigating system is described, said system comprising a focussing member (53) and being configured to transmit THz radiation through said focussing member, said focussing member having. an ellipsoidal focussing surface (55) through which said THz radiation emitted by a THz emitter (71) is transmitted. Alternative focussing members suitable for use in Thz investigating systems have an aspherical convex focussing surface following a specific equation. Furthermore a scanning probe is described, said probe comprising a source of radiation, a focussing member having a first section and a second section, said second section being slidable with respect to said first section and having a sample surface, the system being configured such that radiation emitted from said radiation source enters said first section and exits the focussing member through the sample surface, said system further comprising translating means arranged to translate said first section and said radiation source with respect to the second member, thus scanning the radiation across said sample surface.
(FR) L'invention concerne un système d'enquête THz qui comprend un élément de focalisation, ce système étant conçu pour transmettre un rayonnement THz à travers cet élément de focalisation, cet élément de focalisation possédant une surface de focalisation à travers laquelle le rayonnement est transmis, cette surface de focalisation étant ellipsoïdale.