The band within the electromagnetic spectrum between about 300 GHz and 3 THz is often referred to as terahertz radiation. It is in between the frequency regions in which optical and microwave technologies work well and hence there are not a lot of good sources around. Terahertz radiation is considered to be an upcoming technology in material inspection, quality control, gas sensing, surveillance and security applications, and wireless, short-haul communication.
In a scientific realm, high-resolution THz sources are important for Terahertz spectroscopy, e.g. for astrochemically important molecules and local oscillators for THz telescopes.
Advancing power, tunability, compactness and affordability of Terahertz sources is a very active research area in academia as well at the industrial interface because progress in applications is currently hindered by a lack of suitable sources.
One method to produce THz radiation is to mix two cw infrared lasers in a special kind of semiconductor (low-temperature grown GaAs), which generates their difference frequency that can be tuned into the THz range. Thermal failure was identified to be the limiting factor for THz power and the current investigations are directed on improving heat sinking and understanding temperature characteristics of antennas. We are working to overcome this using diamond heat sinking (see J. Appl. Phys. 2012).
Another area of research is the use of quantum dots for THz generation.