There's a lot of misinformation in the comments posted here. Maybe this bit of information will help. The phrase "terahertz radiation" refers specifically to t

There's a lot of misinformation in the comments posted here. Maybe this bit of information will help. The phrase "terahertz radiation" refers specifically to the band of the electromagnetic spectrum lying between 0.1 THz and 10 THz. The boundaries are arbitrary, and not well agreed upon. Some people say 0.3-30 THz, instead. But the basic idea is the same: it is the realm of the spectrum that lies between the region of microwaves and the region of infrared. It has historically also been called "far infrared" and "submillimeter waves" (submillimeter refers to the wavelength). When people say "terahertz radiation", they are NOT referring to visible light (which has a frequency of hundreds of terahertz). My evaluation of the text of this article is that it is mostly accurate, although sometimes some concepts are skimmed over a bit quickly. There is one blatantly false comment about the propagation distance for terahertz radiation in air being limited to "a few dozen meters" - that's just plain false. But other than that, everything he wrote is reasonable.