Terahertz Imaging Goes The Distance

MILTECH

Illustration only

by Staff Writers
Baltimore MD (SPX) Apr 30, 2007
Terahertz (THz) radiation, or far-infrared light, is potentially very useful for security applications, as it can penetrate clothing and other materials to provide images of concealed weapons, drugs, or other objects. However, THz scanners must usually be very close to the objects they are imaging.

Doubts have lingered over whether it is possible to use THz waves to image objects that are far away, because water vapor in air absorbs THz radiation so strongly that most of it never reaches the object to be imaged.

At the upcoming CLEO/QELS meeting in Baltimore, an MIT-Sandia team will demonstrate the first real-time THz imaging system that obtains images from 25 meters away. The technique takes advantage of the fact that there are a few "windows," or frequency ranges, of the terahertz spectrum that do not absorb water very strongly.

The MIT-Sandia group designed a special, semiconductor-based device known as a "quantum cascade laser" that delivers light in one of these windows (specifically, around 4.9 THz). They shine this light through a thin target with low water content (for example, a dried seed pod), and a detector on the other side of the sample records an image.

A cryorefrigerator maintains the laser at a temperature of 30 Kelvin, where it produces 17 milliwatts of power (as opposed to the microwatts of power typical of pulsed terahertz sources) in order to provide enough terahertz radiation to obtain a decent image. Increasing the power of the lasers and sensitivity of the detectors can potentially enable imaging of thicker objects or imaging of the reflected light, which would be more practical for security applications.

In addition, the development of high-operating-temperature quantum cascade lasers, which operate without the use of cryogenic materials, may also increase the availability of this approach. In the closer term, however, this approach may enable sensing of chemical residues or contaminants in the air.

Email This Article

MILTECH

Radio Controlled Toys Serious Threat To Security Says NATO Official

Moscow (RIA Novosti) Apr 27, 2007
NATO is concerned by the easy access to drone technology in the world, which is in particular used in radio controlled toys, a NATO deputy assistant secretary general said Thursday.

SUPERPOWERS Japan Launches Study On Collective Defence Abe Sees More Assertive Japan Across Entire World Russia Downbeat Ahead Of NATO Talks Royal Navy's Shame	NUKEWARS South Korea Wants Talks With North Korea On Opening Rail Link A Money Laundromat For Nukes Keeps It All That Much Cleaner Iran Stymies Nuclear Non-Proliferation Meeting Mutual Destruction Danger In US Anti-Missile Plan Says Putin
MISSILE NEWS US Army Awards Raytheon Major Patriot Engineering Services Contract Lockheed Martin Concludes Phase II Tests Of Guided MLRS Unitary Rocket Raytheon And US Navy Team For Standard Missile Improvements Taiwan Extends Range Of Cruise Missile	MISSILE DEFENSE Bush Woos Russia On Missile Defense Bush Should Bet On KEI Successful Intercept Claimed In US Missile Defense Test NATO Wants Clarification About Russian Treaty Freeze
AEROSPACE Australia Fears Jet Flight Guilt Could Hit Tourism Nondestructive Testing Keeps Bagram Aircraft Flying New FAA Oceanic Air Traffic System Designed By Lockheed Martin Fully Operational NASA Seeks New Research Proposals	UAV NEWS L-3 Communications Buys Geneva Aerospace And More Boeing-Insitu ScanEagle UAV Logs 1000 Combat Flight Hours With Australian Army Air Force Official Testifies On UAV Executive Agent Issue Maiden Flight Killer Bee UAV
IRAQ WARS US Death Rate Falls In Iraq US Concerned About Iraqi Purge Petraeus Pledges To Assess Surge Democrats Authorize Subpoena For Rice	MILTECH Terahertz Imaging Goes The Distance Radio Controlled Toys Serious Threat To Security Says NATO Official Battlefield Technology Key To Atlantic Strike V Seabees Build Modular Protected Billeting For Warfighters

The content herein, unless otherwise known to be public domain, are Copyright 1995-2006 - SpaceDaily.AFP and UPI Wire Stories are copyright Agence France-Presse and United Press International. ESA PortalReports are copyright European Space Agency. All NASA sourced material is public domain. Additionalcopyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by SpaceDaily on any Web page published or hosted by SpaceDaily. Privacy Statement