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
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.
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
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.