THz photoconductive antennas in pulsed systems and CW systems

In designing terahertz (THz) antennas with high output power and/or high optical-THz conversion efficiency, the photoconductor property is an important consideration. According to the type of the optical excitation, THz antennas can be divided into two categories: THz photoconductive antennas in a pulsed system and THz photomixing antennas in a Continuous-Wave (CW) system. How different excitation types can affect the performance of the antenna is an important issue in THz systems. Thus, the aim of this paper is to investigate and compare THz photoconductive antennas and THz photomixing antennas from an important design parameter point of view; namely the conductance of the photoconductive material substrate which acts as the source for a PC antenna. Through numerical analyses of example systems, it is shown that source resistance of a THz antenna in a CW system is greater than those in a pulsed system. Further, an important practical system setting, the dependency of alignment of two beams in CW systems on antenna gap size is also investigated. It is illustrated that mixing efficiency for large gap antennas is more sensitive to angle between two beams.