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Thursday, April 23, 2009

Terahertz Rays in Security


Terahertz rays aiding in the detection of security threats :

clip_image001A lot of movies show a typical feature which aids the detectives to see through enemies’ camps. This is in the form of a goggle, which would not raise the concern of the adversary, and at the same time, the hero is able to see where the weapons are hidden and in several cases, disable the bombs. X-rays are used to provide this sort of a facility, which is purely fictional. The use of X-ray is limited and the machine cannot be contained to a small goggle.

But scientists are now developing a new technology which might help to an extent in this matter. By the use of terahertz rays, the scientists are hoping to detect all the security threats, like weapons and bombs which might go undetected in the present days. Terahertz rays extend from the upper limit of microwaves to the lower limit of infrared rays.


Now a days, X-rays are used to detect any fracture in the human body, and also in the security checks to check for any weapons. The use of X-rays are limited as they are harmful to the human body causing disintegration of DNA and hence cancers may be precipitated. Terahertz rays or T-rays are considered harmless, that is, they do not predispose the human body to cancers and hence can be used freely. This benefit also applies at the security checks at any airports or public places where T-rays would reflect on any weapons and can be detected easily. For that matter, T-rays have an additional benefit of detecting even plastic objects which often go undetected in X-ray. Scientists' also claim that T-rays can tell the material of the item which is reflected, as it uses a technique called spectroscopy. In this new technology, every item would be reflected in a different colour, so making out a particular item as harmful is easy.

T- rays are not required to be used close to the scanned item, as in the case of X-rays. It can be safely kept at a distance and scanning is done. A lot of research is going on to enhance the capacity of T-rays to use the spectroscopy at a distance.


The possibilities of T-rays are several. They can be used in the pharmacology industry to aid in detection of the contents of the medicines, used to detect tumors in a human body, aid in detecting any defect in the machines. These are just a few of the benefits.

With a lot of benefits under its collar, one wonders what these T-rays are?

They are part of the electromagnetic spectrum, and one area which has been less studied till now. The band width of the T-rays can be between 500gigahertz and 10 terahertz.

Studies have been going on to analyze T-rays, recently particle accelerators have been used to break up the rays and study them.

New technology are being developed to contain the T-rays and direct them accordingly. Also a cost effective method of production need to be developed. The use of synchtron to bend the electrons and produce T-rays is under research. There are still concerns of cost and cooling of the rays, and the size which is important. In addition to these, creation of a continuous wave of T-rays is a challenge the scientists are facing as when T-rays were generated in pulses, it was seen that the bandwidth decreases with distance.
So, how can this be done? Experiments are going on to see whether using two infra red laser machines can be used. The rays produced by the two machines combine to produce a T-ray. A new machine with indium-gallium-arsenide is under consideration.

Also a new technology called Quantum Cascade laser was developed in 1994, which produced rays even in the terahertz range. The wavelengths produced were directly related to the thickness of the semiconductor, which was the reason for success of these lasers. The working of the laser is as follows. An electron is put into the machine which goes to a level and shake up the protons, then fall into another level, emitting phonons. This cycle is repeated and a ray of phonons are produced.

Once the item is detected, a reflection image has to be produced as well. Experiments are going on to produce a detector to create images which can be easily captured by a video camera and reproduced.

There are defects in this new technology as well. But the positive factors are more than the negative factors, so this new technology would be of real help in detecting a lot of security threats.

By Amit Samantaray


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