We detect THz radiation via electro-optical sampling. This technique offers the possibility to sample the THz electric field in time, conveying not only information about its amplitude, but also about its phase. For this purpose, the sample pulse generated by the hybride laser system and the THz radiation are superimposed with a Ge wafer and focused into a ZnTe crystal with a parabolic mirror. Via the linear Pockel's effect the polarisation of the sample pulse is affected by the transient THz field strength, becoming slightly elliptical. A quarter-waveplate transformd the elliptical polarization into a rotation of the polarization. The Wollaston prisma splits the beam into its p- and s-polarized components. The signals of the diodes are subtracted from one another, producing the electrical output signal. By delaying the sample pulse to the THz radiation variably in time, the THz radiation can be detected.