Heterodyne generation of Terahertz radiation and its applications

When two optical beams with a difference in their optical frequencies are spatially overlapped and incident on a photodetector, an optical beat note can be detected at the difference between the two laser frequencies. This principle has been used to develop numerous photonic technologies ranging from optical heterodyne detection used in coherent communications to optical frequency metrology. In this tutorial, we will provide an overview of the development of optical heterodyning for the generation of Terahertz (THz) radiation. The photonic generation of THz has underpinned a wide variety of applications, ranging from next-generation wireless communication systems to high-resolution spectrometers. We will provide an overview of the physical principles of photonic THz generation along with the component and systems-level parameters that affect the signal quality. We will then focus on two applications of heterodyne generation of THz, wireless communications and spectroscopy, and finally discuss future directions for component development.