Terahertz photoconductive antenna efficiency

Terahertz (THz) photoconductive antennas are the most common device for the generation and detection of THz waves and are very different from conventional RF/microwave antennas. One of the major problems of the current photoconductive antennas is that the antenna efficiency is very low, thus it is difficult to obtain high power THz waves. In this paper a comparison of the conventional and photoconductive antennas is made and various parameters and aspects of photoconductive antennas are examined with the aim to maximise its efficiency factor. A new antenna efficiency expression is derived which clearly shows how the efficiency is linked to various parameters. An example is used to demonstrate why the total efficiency is very low and what the major limiting factors are. Recommendations for how to increase the efficiency are presented.