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A 2mm Silicon hyper-hemispherical lens is attached to the facet of the specially designed QCL to collimate the THz output.  (Source: Courtesy of the Capasso Lab, Harvard School of Engineering and Applied Sciences)
Harvard's new 5THz laser probably won't see itself used in any evil genius's plots, but it may help detect volatiles from the just plain evil.

Far-infrared or terahertz lasers can be extremely useful to all sorts of people and organizations. T-rays, able to penetrate a multitude of materials, can be used for such endeavors as medical imaging to detect tumors with no side effects, detecting cracks and irregularities in the space shuttles' seemingly super-delicate heat shield, or finding biological/chemical agents inside sealed packages.

One major drawback to date has been that a typical t-ray emitter must be cryogenically cooled to operate. The typical organic gas type THz laser is cooled to liquid helium temperature.

A newly developed, room-temperature t-ray laser by Harvard University may put the devices in the hands of "average" security, medical and safety engineers everywhere. The team, led by research associate Mikhail Belkin and the Robert L. Wallace Professor of Applied Physics and Vinton Hayes Senior Research Fellow in Electrical Engineering, Frederico Capasso -- with whom another group at Harvard recently showed their work in nanowire LEDs -- of Harvard's School of Engineering and Applied Sciences used a specially designed Quantum Cascade Laser (QCL) to produce the terahertz level beam.

To produce THz radiation from a mid-infrared laser device, the group designed a QCL that emits two frequencies of light concurrently. The THz radiation itself is created by difference-frequency generation inside the laser medium. Their emitter kicks out t-rays of a respectable 5THz at a few hundred nanowatts of power. Microwatts are achievable with commercially available thermoelectric coolers, says Belkin. "Further, there is the potential of increasing the terahertz output power to milliwatt levels by optimizing the semiconductor nanostructure of the active region and by improving the extraction efficiency of the terahertz radiation."

Not only is the Harvard t-ray laser operable at room-temperature, due to its construction process, it should lead to relatively inexpensive and mass-producible detection and imaging systems. Capasso explains, "Terahertz imaging and sensing is a very promising but relatively new technology that requires compact, portable and tunable sources to achieve widespread penetration. Our devices are an important first step in this direction. We believe our THz source has great development potential because the nanoscale material used was grown by Molecular Beam Epitaxy, a commercial and widely used thin film growth technique which 'spray paints' atoms on a surface one layer at a time."

The multi-university team's work, which includes Harvard, Texas A&M and the Institute of Quantum Electronics in Zurich, will be published in today's issue of Applied Physics Letters.



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This article is over a month old, voting and posting comments is disabled

By puffpio on 5/20/2008 12:22:09 AM , Rating: 1
terabytes of storage per disc?




By nomagic on 5/20/2008 12:52:36 AM , Rating: 2
If I have to guess, there will not be a next generation of optical discs. It will be replaced by something else such as holographic storage media.

However, if there is one more generation of optical disks, just imagine the possibility! Hundreds of hours of Hi-Def p0rn on one single disk...


By dflynchimp on 5/20/2008 5:13:01 AM , Rating: 3
quote:
Hundreds of hours of Hi-Def p0rn on one single disk...


That's a lot of eggs in one basket >.>


By amanojaku on 5/20/2008 1:21:28 AM , Rating: 5
If T-Rays were to be used for optical storage we would be taking a step backwards. Think megabytes of storage, if that. T-Rays (1mm-100µm) operate in between microwaves (1-300mm) and infrared(1mm-705nm.) That's MUCH larger than the wavelengths used by CDs (780nm) and DVDs (650nm.) Blu-Ray and HD-DVD both use blue lasers at 405nm. To get more storage density the wavelength needs to be less than 400nm.

The point behind T-Rays is that the larger wavelength allows for greater penetration of objects. The real benefit is that T-Rays are non-ionizing: they don't strip atoms of their elections. This means they shouldn't damage living tissue the way X-Rays can.

For easier reference:
mm > µm > nm > pm > fm


By MrJim on 5/20/2008 5:54:40 AM , Rating: 2
You gotta love the International System of Units.


By mezman on 5/21/2008 2:50:40 PM , Rating: 2
Yep.
quote:
The point behind T-Rays is that the larger wavelength allows for greater penetration of objects.


This is known as the Skin Effect.

http://en.wikipedia.org/wiki/Skin_effect

Simply put, the higher the frequency, the less deep the EM radiation will penetrate. This can be seen in practice by comparing how a turkey cooks in the oven (IR radiation with wavelengths in the nm to um range) and the microwave (Microwave radiation with wavelengths in the mm range).


mini Death Star?
By Diesel Donkey on 5/19/2008 11:04:40 PM , Rating: 3
I wonder if that hyper-hemispherical lens is based on the design for one of the Death Stars. It certainly seems possible since that design did originate a long, long time ago, and it was used for similar purposes.




RE: mini Death Star?
By 325hhee on 5/20/2008 10:14:21 AM , Rating: 2
No no, space temp is too cold, it's absolute zero, or colder, so the lazer wouldn't function, we need to take it one step at a time, like with tepid water temperatures, or pool water temp, or sea water temp. If we can get the lazer to work in sea water temps, we can then start mounting them onto sharks.

Just start from there :)


RE: mini Death Star?
By Smartless on 5/20/2008 2:35:21 PM , Rating: 2
And we will hold the world ransom for 1 Million Bajillion Dollars.


Title image change request.
By eetnoyer on 5/20/2008 6:28:01 AM , Rating: 2
I personally think the perfect fit for this article would be a tricorder scan. Seems like that's where this technology may be headed. More Star-Trek tech becoming reality.




RE: Title image change request.
By HVAC on 5/20/2008 10:13:20 AM , Rating: 2
I'm thinking that also.

Vary the output power to vary the depth of tissue penetration and, voila!, cheap subcutaneous imaging. Really cool if it can punch all the way through the human without cooking them.

Also, one could introduce marker drugs that target cancer cells for cheap quick go/nogo scans. Add specific wavelength ionizing tails to the drug and your laser could cook (destroy) the cancer cells, leaving healthy tissue alone. Radiation therapy with minimal side effects.


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