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THzscience.nl
What is THz radiation?
Terahertz (THz) radiation is electromagnetic radiation with a frequency of around 1 THz, or one million times one million hertz. In the electromagnetic spectrum, it is roughly located between the visible light domain and the microwave domain.
(Click on thumbnail for electromagnetic spectrum)
Is THz radiation similar to radioactivity or nuclear radiation?
No! Absolutely not. The two are completely different. THz radiation is low frequency electromagnetic radiation, a kind of high-frequency radio waves or, depending on your point of view, a kind of low frequency light.
Is THz radiation dangerous for human beings?
Not as far as we know. THz radiation is non-ionizing electromagnetic radiation. Non-ionizing means that the energy of a THz photon is too small to free electrons from atoms and molecules to which they are normally tightly bound. This means THz photons cannot cause any damage to living cells. There's another reason not to fear THz radiation: In the range of temperatures in which we humans live, every object, including our own body, emits THz radiation. If THz radiation were dangerous, we'd all be dead. As long as the power of the THz radiation used doesn't significantly rise above this background level, everything should be safe. When the power is significantly higher, all  bets are off. So far, however, there have been no reports of human beings being adversely affected by THz radiation
What's the use of THz radiation?
Well, that's one of the things we're trying to find out. An interesting application is imaging. This was invented by dr. M.C. Nuss and coworkers at, what was then, AT&T Bell Laboratories (B. B. Hu and M. C. Nuss, Opt. Lett. 20, 1716 (1995)). THz radiation goes through many everyday objects that don't contain water or metals. Water and metals effectively absorb/reflect THz radiation. Humans consist mostly of water and therefore THz radiation cannot be used to look inside humans. THz radiation does, however, penetrate cardboard, paper, dry wood, various paints, many plastics, many ceramic materials. The idea is to use THz radiation to image the insides of something without having to destroy the package: Non-destructive testing. Some examples are given on the THz images page (see link on the left). Another application is spectroscopy: Many organic molecules absorb THz light at specific THz frequencies. This THz absorption fingerprint can be used to identify these molecules.
Is THz radiation different from far-infared radiation?
In fact, the terms are frequently used simultaneously. Before about 1995, the word "far-infrared" was frequently used. "Far-infrared" did, however, conjure up images of old-ish, rather boring physics. With the advent of new techniques to generate and detect "far-infrared" radiation, the term THz was used more and more but both terms describe the same frequency range in the electromagnetic spectrum.
Why this "THzscience.nl" website?
Because. It seems like a good idea to give people a bit more of a background on what we see as an exciting science. We could have hosted this website at the university too, but the formatting guidelines were just a bit too restrictive for our taste.
These questions are mostly asked by people who know very little about THz radiation or, indeed, physics. If you have questions that are not found here, and you crave for an answer, please send me an email and I will consider incorporating it here.