Terahertz (THz) technology is now standing at the lab doorstep to the real world applications such as spectroscopy, biological sensing, security imaging, detection of dangerous or illicit substances, and ultrafast data transfer. Photoconductive antennas (PCAs) are one of the most frequently used devices for THz-wave generation and detection in established THz measurement and spectroscopy setups owing to their compactness and operation at room temperatures. However, the performance of PCAs is limited by low absorption of pump laser radiation in the antenna gap, long lifetime of photoexcited carriers, and antenna’s low thermal tolerance and instability. The recently proposed approach to overcome these obstacles relies on optical nanoantennas, i.e., resonant nanostructures that are capable to transform incident light into a strongly localized near -field within THz antenna gap. This chapter is intended to systematize the main results obtained in this promising area of hybrid optical-to-terahertz PCAs and photomixers. We summarize the main results on hybrid THz antennas, compare the approaches to their implementation, and offer further perspectives of their development.
