Development of terahertz time-domain photoconductive antenna and antenna arrays

The terahertz (THz) region of the electromagnetic spectrum lies between microwaves and optical waves and holds great potential for many applications. THz technology can be used in various fields, from non-destructive imaging systems to material characterization. It also offers significant potential in communications by enabling higher data rates. However, the generation and detection of THz waves are limited by various challenges, such as the mobility of semiconductors and low energy levels. In recent years, significant progress has been made in the generation of consistent THz waves. The use of photo-absorbing semiconductor structures and metal terahertz antennas has been effective in generating THz radiation. This method involves photon absorption, which produces moving electron-hole pairs, and these pairs oscillate at THz frequencies, creating an ultra-fast photocurrent. However, improving the efficiency of these systems remains a major challenge. There are two main approaches to improving the optical-to-electrical conversion efficiency in THz systems: Developing special semiconductor active layers to enhance photon absorption and carrier generation and activating surface plasmonic waves in antenna active regions to increase conversion efficiency. Additionally, the design of antennas that can effectively emit broadband terahertz radiation. High-gain antennas can make THz radiation more efficient and improve signal detection on the receiver side. The radiation emitted by terahertz photo-conductive antennas (PCAs) needs to be characterized in the time domain, as traditional frequency-domain characterization is insufficient for systems that use broadband short-pulse signals. In this context, analyzing antennas in the time domain can be much more efficient. As a result, the design of broadband antenna arrays and time-domain analysis plays a crucial role in the development of terahertz PCAs. Furthermore, for imaging applications and potential future communication systems, improving the performance of terahertz radiation, along with the ability to perform beam-steering will also be important. Therefore, the development of beam-steering antenna arrays is crucial. In this regard, studies aimed at developing optical-component-assisted phased terahertz antenna arrays or lens-assisted switched antenna arrays at terahertz frequencies is critical. Considering the information given above, in this thesis, photo-conductive antennas and antenna arrays in the 0.8–2 THz band have been developed, designed, and optimized based on theoretical studies in the time domain. The entire work has been conducted in the time domain, and system requirements for using antenna arrays as phased arrays have been determined. Due to the size and semiconductor technology required for terahertz antennas, their fabrication may require innovative approaches. Additionally, due to these same reasons, the packaging of antennas also presents challenges. Optimized antenna designs have been fabricated and packaged to be ready for measurement, considering these problems.