Experimental Determination of the Unipolarity of Pulsed Terahertz Radiation

Energy, pulse duration, and frequency of the spectral maximum are important characteristics of pulsed terahertz radiation. The unipolarity of radiation is another characteristic that is paid less attention to. This paper demonstrates possible ways how to determine the presence of unipolarity in the radiation of pulsed terahertz sources. The first approach is based on integrating the time dependence of the field strength in the far zone obtained experimentally. The second approach uses radio-technical equipment by means of recording low-frequency components of pulses, which exist in the unipolar terahertz radiation. The results of experiments are presented with recording the unipolar component of THz pulses by both methods. The existence of unipolarity is shown for pulses from some types of terahertz radiation sources. Estimations are made for the electric area and the degree of unipolarity of the pulsed radiation for the first time.