Terahertz-wave Parametric Sources

Terahertz waves are the electromagnetic radiation whose frequency ranges from millimeter waves to the far infrared, shown in Figure 1. While both sides of this range have had a long history of research and development, leading to already commercially available sources, detectors, meters, and many additional devices, the terahertz wave range is still in its infancy, representing the last unexplored part of the electromagnetic spectrum between radio waves and visible light. This delayed development was mainly caused by the difficulty of producing reliable and strong terahertz wave generators, as well as the unavailability of sensors that can detect this unusual radiation. Technology extrapolation from both neighboring sides has been facing difficult problems: Up-conversion from the microwaves is inefficient due to the frequency being too high; down-conversion from the infrared is limited by the energy gaps.