Abstract:
The need for low-loss, low-dispersion waveguides for THz radiation has lead to the development of several types of metallic waveguide because of the high conductivity of metals at THz frequencies. In this thesis I examine two of these designs. The first is a hollow silver tube, the second two parallel copper wires. The behaviour of the first can be described by the well-known microwave theory but the behaviour of the second guide is still poorly understood. Sample sets of both were produced in several lengths, and the wire-edge separation was also varied in the case of the two-wire design. The two sample sets were characterized by THz-TDS and the results compared for losses, coupling factors and dispersion. The results for the tubes compared well to the theory displaying a predictable cutoff frequency, large dispersion and large losses. The two-wire design displays negligible dispersion as predicted for a two conductor transmission line by the microwave theory. The measured losses propagation losses at frequencies below 0:6 compared well to predictions while losses at higher frequencies could not be readily explained.