Within this chapter details of the generation of longitudinally polarised terahertz radiation within non-linear optical crystals are presented. The design of the different optical setups used are explained along with the results obtained from these setups. Two optical setups were designed and built using two different types of non-linear optical crystals, ZnTe (Sect. 7.3) and magnesium-oxide-doped stoichiometric lithium niobate (MgO:SLN) (Sect. 7.4). These different crystals required different pump geometries. Whilst the ZnTe crystal allowed for a co-linearly phase-matched pump scheme, the MgO:SLN crystal required a non-co-linear tilted-pulse-front pumping scheme. The terahertz radiation generated from both of the non-linear optical crystals was detected using an electro-optic balanced detection scheme with a movable probe beam allowing for both the spatial and temporal mapping of the terahertz electric field. The design and implementation of both the pumping schemes and electro-optic detection scheme is detailed within this chapter.