Development of a time-domain spectroscopy system for the characterization of terahertz photoconductive antenna and antenna arrays

The rapid growth in the terahertz technology necessitates high-performance components and systems to accomplish the expected performance of the state-of-the-art terahertz systems. Terahertz time-domain spectroscopy and imaging systems have become the most widely used technique for a wide range of applications in the terahertz band due to their unique functionalities. In these systems, photoconductive antennas and arrays are one of the most common approaches for the generation of the terahertz signals. In the last decade, photoconductive sources have shown significant progress, improving the technology level for the generation and detection of the terahertz signals. Although the efficiency of the terahertz photoconductive antennas have had some improvement, the low power level of the generated terahertz signals, which has stemmed from the low optical-to-terahertz conversion efficiency is a drawback that still faces the terahertz time-domain spectroscopy and imaging systems. Thus, these components have to be characterized for their beam or radiation properties, which are crucial for the system performance since they have a direct effect for the development of some terahertz applications, also they can further improve the performance of these components significantly. A novel modified terahertz time-domain spectroscopy system is proposed to characterize the time-domain radiation pattern of terahertz photoconductive antennas. The proposed system resolves the radiation pattern spatially in the two major planes. The theoretical calculations for the proposed setup, which is based on the optical path difference method are presented and compared with the measurements. The proposed method gives a detailed time-domain characterization of the gallium arsenide based terahertz photoconductive antennas and beam-steering arrays. The characterized antennas are also examined in the simulation environment and the results are compared with the measured radiation patterns.