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Topic: Terahertz

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	Terahertz waves penetrate the world of imaging - optics.org
		Terahertz waves are electromagnetic waves that have a frequency of between 100 GHz and 30 THz and lie between the infrared and microwave parts of the spectrum.
		To date, terahertz waves are usually generated by illuminating a piece of semiconductor, such as gallium arsenide, with femtosecond pulses from a solid-state laser such as a Ti:sapphire laser.
		Coherent detection of the pulses is achieved by illuminating a second crystal with both the terahertz pulses and a portion of the visible femtosecond pulses that is split off from the original beam and has undergone a suitable time delay.
	optics.org /articles/ole/7/9/5/1 (1788 words)

	Time-resolved Terahertz spectroscopy
		Because the wavelength of terahertz radiation is much longer than that of visible light, it is not possible to create narrow beams such as those from a laser.
		Instead, the terahertz beam, which has a diameter of 2 mm at the point where it is generated, diverges strongly, and a large mirror is needed to capture all the radiation.
		In time-resolved terahertz spectroscopy, the terahertz pulses described above are used as probe pulses to probe the state of a sample after excitation by a pump pulse of visible light.
	www.chemphys.lu.se /kfresearch/fac-trts.html (1019 words)

	Handheld terahertz wand to unmask terrorists - 12 July 2004 - New Scientist (Site not responding. Last check: 2007-11-03)
		But using terahertz radiation to produce X-ray-like images of passengers is likely to be unacceptable for routine use, as it will allow security staff to see the people they are scanning as if they were naked.
		Terahertz waves occupy a relatively unexplored part of the electromagnetic spectrum between microwaves and infrared.
		By sending short pulses of terahertz waves at a person and recording what is reflected it is possible to image the materials hidden next to the body (New Scientist print edition, 14 September 2002).
	www.newscientist.com /article.ns?id=dn6118 (493 words)

	ESA Portal - Space camera blazes new terahertz trails
		Terahertz waves occupy a portion of the spectrum between infrared and microwaves, from 10¹¹ to 10¹³ Hertz.
		The main advantage of a terahertz imager is that it does not emit any radiation; it is a passive camera capturing pictures of the natural terahertz rays emitted by almost everything, including people, rocks, water, trees and stars.
		In space astronomy, observing terahertz frequencies could provide answers to some key questions on how galaxies were formed in the early universe, and how stars form, and have been forming, throughout the history of the universe.
	www.esa.int /export/esaCP/SEMZ1R1A6BD_index_0.html (1628 words)

	UVA LABORATORY FOR TERAHERTZ SCIENCE
		The terahertz region of the electromagnetic spectrum encompasses wavelengths of 0.01 to 1.0 millimeter.
		Terahertz technologies enable a diverse set of investigations in local laboratories, at national laboratories and observatories, and in aircraft and spacecraft.
		It is exploring terahertz spectroscopy as a means of studying critical problems in the dynamics of biological systems, such as the geometry of protein folding.
	www.astro.virginia.edu /class/oconnell/LTS (867 words)

	Terahertz radiation: applications and sources - The Industrial Physicist
		CW terahertz technology has long interested astronomers because “approximately one-half of the total luminosity and 98% of the photons emitted since the Big Bang fall into the submillimeter and far-infrared,”; says Peter Siegel of the Jet Propulsion Laboratory (Pasadena, CA), and CW THz sources can be used to help study these photons.
		The terahertz pulse is distorted by selective absorption as it passes through a sample, causing delays in its arrival time at the detector.
		Although the practical application of terahertz radiation is in its infancy, the recent availability of reliable sources in the 0.3- to 5-THz range may have a wide-ranging impact on science, industry, and medicine.
	www.aip.org /tip/INPHFA/vol-9/iss-4/p27.html (2034 words)

	Terahertz Imaging
		At one terahertz, each cycle is one picosecond, and the wavelength in free space is roughly 300µm.
		These waves, known as terahertz radiation, are in a waveband that is the overlap of what is normally regarded as microwave radiation and far-infrared light.
		However, recent technologies using terahertz radiation have been developed, which are intended for applications such as medical imaging and surveillance.
	pami.uwaterloo.ca /tizhoosh/terahertz_imaging.htm (175 words)

	RPI Center for Terahertz Research - About Us
		Using the relatively unexplored terahertz portion of the electromagnetic spectrum, they are creating innovative imaging and sensing technologies that hold enormous potential in biomedical imaging, genetics diagnostics, microelectronics, and the chemical and biological materials identification fields.
		Together, these researchers are overcoming significant challenges posed by the lack of understanding of the fundamental physics that underlie this large – and historically inaccessible – portion of the electromagnetic spectrum.
		Rensselaer's Center for Terahertz Research stands at the forefront of terahertz technology, a science still in its infancy yet expected to become one of the most promising research areas for transformational imaging in the 21st century.
	www.rpi.edu /terahertz/about_us.html (712 words)

	Terahertz Systems
		Terahertz frequencies correspond to the rotational energy level transitions of important molecules in biology and astrophysics.
		However, development of terahertz technologies is impeded or even prevented by the lack of standards and the inability to perform precise measurements to characterize noise, power, dielectric constants, and scattering parameters of systems and components operating at terahertz frequencies.
		Abstract: Terahertz frequencies are among the most underdeveloped of the electromagnetic spectra, even though their potential usefulness can have a major impact on many areas of life today.
	www.ieeeboston.org /edu05s/2005fall/terahertz_systems.htm (4044 words)

	ESA Portal - Improving Daily Life - Space camera blazes new terahertz trails
		However, terahertz waves are very interesting as they possess characteristics of both their neighbours: terahertz waves can pass easily through some solid materials, like walls and clothes, yet can be focused as light to create images of objects.
		Terahertz imaging is rapidly becoming recognised as a totally new diagnostic technique.
		Terahertz waves are also able to penetrate the uppermost layers of skin, making the early detection of skin cancers an interesting possibility.
	www.esa.int /export/esaCP/SEMZ1R1A6BD_Improving_2.html (1624 words)

	Terahertz breakthrough at BESSY (March 2003) - News - PhysicsWeb
		Terahertz radiation can be used in applications as diverse as biological imaging and the study of semiconductors.
		Terahertz radiation is found at the low-energy end of the spectrum and corresponds to wavelengths between about 1 mm and 15 microns.
		Wüestefeld and co-workers therefore adjusted the magnetic fields in the storage ring to produce a special “low-alpha” mode in which the length of the bunches was comparable with the wavelength of terahertz radiation.
	www.physicsweb.org /article/news/7/3/9 (332 words)

	SPACE.com -- First Image from Revolutionary T-ray Camera; Sees through Fog, Clothing and into Deep Space
		Low frequency versions of terahertz waves are known as millimeter waves, and they behave much like radio waves.
		At higher frequencies, the terahertz waves straddle the border between radio and optical emissions.
		Terahertz waves are unique because they can pass easily through some solid materials, yet they can also be focused as light to create images of objects behind the obscuring material.
	www.space.com /businesstechnology/technology/t-ray_camera_020613.html (831 words)

	Scientific Prospects for a Terahertz Telescope
		Further tracers of the WIM in the terahertz band are the Hydrogen alpha series recombination lines 19-18 at 1.040 THz, and 17-16 at 1.466 THz (Towle et al.
		A 3-meter terahertz telescope will be able to detect the 205 micron NII line in nearby galaxies, depending on the fraction of the emission that arises in a compact nuclear region.
		However, a 6-meter-class terahertz telescope equipped with a bolometer array camera (12'' resolution) would be required before we could effectively compete with existing cameras such as MAMBO on the IRAM 30-meter at 1.3 mm, SCUBA on the JCMT at 800 microns, and SHARC2 on the CSO at 350 microns.
	cfa-www.harvard.edu /srlab/secure/rxlabTerahertzScience.html (4042 words)

	Terahertz for Imaging
		But terahertz isn't harmful to humans the way X-rays are because they emit at lower energy levels.
		A terahertz device might be used to determine different types of pollutants in the environment and it may be possible to test surrounding air for bacteria like anthrax.
		Research is preliminary and the terahertz device is still being tested, but its possibilities are endless.
	www.annieappleseedproject.org /terforim.html (632 words)

	Airports test terahertz imaging - optics.org
		This means that a terahertz imaging system can potentially reveal the presence of concealed objects such as knives and guns and also smuggled items such as narcotics, alcohol and money.
		He says that the big advantage of their detector technology is that it is passive, meaning that no illumination source of terahertz waves is required.
		A Cambridge-based start-up Teraview is also developing active terahertz spectroscopy systems for the use in pharmaceuticals industry and medical fields.
	optics.org /articles/news/11/7/15/1/terahertz (435 words)

	TeraView
		The ‘terahertz gap’ – where until recently bright sources of light and sensitive means of detection did not exist – encompasses frequencies invisible to the naked eye in the electromagnetic spectrum, lying between microwave and infrared.
		Terahertz technology also produces faster results than X-ray and in the pharma industry enables non-destructive, internal, chemical analysis of tablets, capsules and other dosage forms.
		Moreover, the non-ionizing properties of Terahertz radiation and the relatively low power levels used indicate that it is safe.
	www.teraview.co.uk /terahertz.asp (243 words)

	Terahertz Imaging May Reduce Breast Cancer Surgeries
		Researchers used light waves in a newly explored region of the electromagnetic spectrum--the terahertz region--to examine excised breast tissue and determine if the removed tissue margins were clear of cancer, with good results.
		For the first time, however, terahertz imaging has the potential to eliminate the need for subsequent procedures by allowing the surgeon to analyze tissue samples during the initial excision procedure.
		Terahertz light is located between the infrared and microwave portions of the electromagnetic spectrum.
	www.medicalnewstoday.com /medicalnews.php?newsid=42279 (675 words)

	RPI Center for Terahertz Research - THz Solid-State Electronics
		The terahertz range – which lies between the frequency ranges of electronic and photonic devices – is often referred to as the "terahertz gap" because of the lack of both high-power, low-cost, portable room temperature THz radiation sources and efficient detectors to collect and record those signals.
		The upper frequency limit of transistors operating in conventional regimes is limited by the transit time of carriers under the gate, for a field effect transistor, or across the base and collector depletion region, for a bipolar junction transistor.
		On the other hand, since the quanta of terahertz radiation are much smaller than the thermal energy at room or even at liquid nitrogen temperatures, photonic devices using interband or intersubband transitions have to operate at cryogenic temperatures.
	www.rpi.edu /terahertz/res_solid_state.html (420 words)

	Superhuman vision – seeing with terahertz
		Terahertz waves, invisible to the naked eye, are being used to provide 'superhuman vision'.
		Terahertz waves lie between the highest radio frequencies and the far infrared representing the last unexplored frontier of the radio and light wave spectrum.
		The Glasgow group develop devices that allow the terahertz waves to be deftly manipulated, often in collaboration with developers of terahertz imaging and spectroscopy systems.
	www.royalsoc.ac.uk /exhibit.asp?id=4661 (481 words)

	Terahertz Imaging and Spectroscopy
		The part of the electromagnetic spectrum between millimeter waves and far infrared is referred to as terahertz radiation or T-rays.
		Such a source can be used for high resolution remote subsurface imaging, with spatial and depth resolution better than 1 mm, enabling differentiation of mines from other similar size objects, and is therefore a candidate to augment ground penetrating radar as a means of mine detection.
		APL has initiated a program to develop a sensor for mine detection using an ultra-fast-laser based terahertz system, with the objectives to determine the best THz source, the imaging capabilities, propagation and penetration in soil under different environmental conditions, and spectroscopy of different explosives.
	www.jhuapl.edu /areas/sciencetech/SensorTechnology/TerahertzImaging.asp (306 words)

	NJIT physicist sees terahertz imaging as ultimate defense against terrorism
		Since 1995, Terahertz imaging has grown in importance as new and sophisticated devices and equipment have empowered scientists to understand its potential.
		When a Terahertz system is used correctly, people can see through concealing barriers such as packaging, corrugated cardboard, walls, clothing, shoes, book bags, pill coatings, etc. in order to probe for concealed or falsified materials.
		Terahertz radiation also poses minimal or no health risk to either the person being scanned or the THz system operator.
	www.eurekalert.org /pub_releases/2005-10/njio-nps103105.php (621 words)

	Tailored Terahertz Pulses from a Laser-Modulated Electron Beam
		Researchers at the ALS have demonstrated a new method to generate tunable, coherent, broadband terahertz radiation from a relativistic electron beam modulated by a femtosecond laser.
		The reason for this "terahertz gap" has been the scarcity of intense broadband sources of radiation in the terahertz frequency range.
		The earlier demonstration of femtoslicing at the ALS as a source of ultrafast x rays showed that we can manipulate the distribution of an electron beam using a short-pulse laser on a time scale of several hundred femtoseconds.
	www.als.lbl.gov /als/science/sci_archive/135terahertz.html (1052 words)

	EETimes.com - Waveguide principle found for terahertz imaging
		While performing experiments designed to enhance the focusing of terahertz waves, Daniel Mittleman and Kanglin Wang found that a simple wire about 6 mm in diameter is all that is needed to form the terahertz waveguides critical to the technique.
		Terahertz imaging made national headlines in the wake of the 9/11 attacks as a new approach for detecting explosives and nonmetal lethal devices.
		Terahertz fields with wavelengths longer than infrared radiation but shorter than radio frequencies are sensitive to a range of materials denser than clothing but not as dense as bone or metal, which can be picked up with X-rays.
	www.eetimes.com /showArticle.jhtml?articleID=54200109 (866 words)

	What is terahertz? - a definition from Whatis.com - see also: THz
		The terahertz is used as an indicator of the frequency of infrared (IR), visible, and ultraviolet (UV) radiation.
		The terahertz is not commonly used in computer and wireless technology, although it is possible that a microprocessor with a clock speed of 1 THz might someday be developed.
		At present, the terahertz is of interest primarily to physicists and astronomers.
	searchnetworking.techtarget.com /sDefinition/0,,sid7_gci752929,00.html (239 words)

	Oxford Terahertz Photonics Group (Site not responding. Last check: 2007-11-03)
		The Oxford Terahertz Photonics Group is a research group within the sub-department of Condensed Matter Physics, which is part of the sub-faculty of Physics at the University of Oxford.
		We have developed a terahertz radiation detector that measures both the amplitude and the polarization of an electric field pulse as a function of time.
		Terahertz (THz) emission from arsenic-ion implanted GaAs surfaces is studied via experiment and a three-dimensional carrier dynamics simulation.
	www-thz.physics.ox.ac.uk /thzhome.html (396 words)

	Terahertz rays beam past hype \| Technology \| Guardian Unlimited Technology
		His compact terahertz laser, which works like an x-ray but without the health risks, can see through thin layers and even identify what is underneath.
		Terahertz frequencies lie between microwaves at the low end, and the infrared end of the visible spectrum at the top end.
		Seven years ago, "terahertz rays" were touted as a replacement for dental x-rays, but they have yet to make it into your dentist's surgery.
	technology.guardian.co.uk /weekly/story/0,,1771607,00.html (965 words)

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