We know from physics that it is particularly difficult to pass light through a hole smaller than half the wavelength of the light used. With the help of fellow scientists, researchers at Delft University of Technology have managed to provide insight into this process by conducting measurements using what is known as Terahertz radiation (THz radiation). This is far-infrared light with an approximate frequency of 1012 Hz. This type of radiation allows the researchers to measure the force of the penetrating light’s electrical field near the hole and not, as is usual, the intensity of the penetrating light. The electrical field’s values reveal much more about how light behaves in such situations than intensity can. Measurement of the strength of the electrical field is done with great precision by measuring the refractive-index of a crystal near the hole using a laser beam. The crystal’s refractive index varies (very slightly) when in a variable electrical field. By measuring the variations in the refractive index, conclusions can be drawn on the strength of the light’s electrical field near the hole.

Bouwkamp
‘This process has never been mapped properly, mainly because the technology was not available to do so,’ says Planken. The experiments largely confirm, for the first time, what is known as the Bouwkamp model, named after a Dutch researcher who worked at Philips and who in 1950 created a theoretical model for the way in which light passes through small holes. For instance, the strength of the electrical field, as predicted by Bouwkamp, is greatest at the edge of the holes and the field’s strength indeed decreases in with decreasing frequency of the THz light used. In their experiments, the researchers also discovered that even if the hole is up to fifty times smaller than the wavelength used, sufficient light can pass through to allow measurements near the hole; an extremely difficult task using other methods. This technique has also enabled the researchers to record the entire process, allowing them to observe, slowed down a thousand billion (1012) times, how the light exits the hole and subsequently how the light waves move outwards in the same way as ring-shaped ripples caused by a stone thrown into a pond.

Applications
The findings of Planken and his colleagues are not just significant from the point of view of fundamental science. They can help develop the use of Terahertz microscopy (THz). In the long term, Planken wishes to use the tiny holes as an improved source of THz light. The smaller these source holes become, the sharper the images that can be created using this technique and the easier it will be to measure small quantities of substances.

Terahertz radiation (with a frequency of about 1012 Hz) is a type of electromagnetic radiation which is increasingly used to create images. After all, many materials, such as paper, plastics and clothing, are transparent to THz radiation, while they block visible light.

Terahertz microscopes do not yet provide such sharp images. The development of stronger and smaller sources and more sensitive detectors will improve the viability of creating images of, for example, biological cells using THz radiation.

For images and movies, please visit http://www.optica.tudelft.nl/research/thz/THzprojects/hole.asp

In the past, the paths of laser physicists and high-energy-particle physicists rarely met. But times are changing. The extreme fields produced by emerging high-intensity lasers hold increasing promise as a means of producing high-energy particle beams. On page 390 of this issue [1], Serge Bielawski and colleagues describe the ability to coherently control the radiative behaviour of the electrons in the storage ring of a conventional particle accelerator with a pulsed laser, and in doing so demonstrate a bright, tunable source of radiation in the difficult-to-reach terahertz region of the electromagnetic spectrum. The result further widens the potential of existing accelerator facilities as sources of useful radiation.

The principle behind the authors’ demonstration is essentially the same as that used in a conventional radio transmitter. When an charge (q) is driven to oscillate back and forth — such as up and down the length of a radio antenna — it will radiate with a power given by the Larmor equation. Instead of using conventional electronics to drive the periodic oscillation of electrons in an antenna, the authors use a shaped laser pulse to modulate the charge density in an electron packet of a relativistic electron beam, so that when its path is bent by a simple dipole magnetic it radiates at a frequency determined by the modulation period (see Fig. 1).

Figure 1 : Generation of bright, tunable, narrowband, THz radiation by the interaction of a laser and a relativistic electron beam.
Injecting an appropriately shaped pulse into the undulator region of a conventional electron accelerator storage ring periodically modulates the longitudinal distribution of charge in a relativistic electron beam packet. Subsequent bending of the path of this packet causes the emission of radiation at wavelengths determined by the period of modulation. Tuning this period enables tuning of the subsequent radiation.
Full size image (25 KB)

The advantages of such an approach are manifold, the most potent being the relativistic enhancement to the power emitted by a beam of particles travelling at close to the speed of light. The relativistic correction to the Larmor equation2 includes the ratio of the energy of the particles in the beam to their rest mass raised to the power of four. For the beam of 600 MeV electrons (whose rest mass is 0.511 MeV) used by Bielawski et al., this enhances the radiant power (compared with non-relativistic electrons) by more than 12 orders of magnitude. Although this correction ignores the spectral distribution, this is exactly what is being tailored here.

In addition, the dependence of the non-relativistic Larmor equation on the square of the total charge enables further improvements in radiant power, as is exploited in conventional table-top THz sources [3, 4]. Although Bielwaski et al. did not achieve complete modulation of the electron bunch, there is no reason in principle why the entire bunch should not contribute. Future investigation should provide new insight into the collective behaviour of the electrons subject to ponderomotive forces in combined electric and magnetic fields. It is also worth remarking that the radiation that Bielawski et al. report is emitted as each electron executes approximately half a cycle, but the power radiated is independent of the acceleration time and would be a mixture of edge and dipole radiation. Further, the superposition of radiated fields from all the density modulations would change the spectral content as a function of angle in a unique way. This type of source can in principle be used with phase-detection techniques similar to those exploited by table-top sources[5].

But perhaps the most important advantage is the relatively straightforward way in which the frequency of the emitted THz radiation can be tuned, by simply changing the modulation period of the laser beam. The terahertz region of the electromagnetic spectrum is particularly difficult to generate — being too high in frequency to be reached by conventional electronics and too long in wavelength to be reached by most optical sources. This underexploited region offers enormous potential for discovery and for gaining an understanding of some of the fundamental mechanisms responsible for the behaviour of materials. Indeed, the evolution of terahertz techniques to study the dynamical quantum behaviour in materials has advanced very dramatically during the past decade, and will continue to do so with ultrafast table-top lasers, optical switches and phase-sensitive detectors [3, 4].

Table-top sources are adequate for most applications, and can produce high peak power6. However, there remain some regimes that can only be reached using large-scale facilities such as particle accelerators. Higher brightness and higher average-power terahertz sources are expected to have many important applications, from fundamental studies of linear and nonlinear dynamical processes in physics, chemistry, materials science and biology to real-time imaging applications relevant to non-destructive evaluation and useful in the security and medical fields [7]. The source of bright, narrowband, tunable THz radiation demonstrated could prove useful in this endeavour.

References

1. Bielawski, S. et al. Nature Phys. 4, 390–393 (2008).
2. Jackson, J. D. Classical Electrodynamics (Wiley, New York, 1975).
3. Orenstein, J. in Handbook of High Temperature Superconductivity: Theory and Experiment (eds Schrieffer, J. R. & Brooks. J. S.) Ch. 7 (Springer, Hamburg, 2007).
4. Cooke, D. G. et al. J. Appl. Phys. 103, 023710 (2008).
5. Shen, Y. et al. Phys. Rev. Lett. 99, 043901 (2007).
6. Yeh, K.-L., Hoffmann, M. C., Hebling, J. & Nelson, K. A. Appl. Phys. Lett. 90, 171121 (2007).
7. Tonouchi, M. Nature Photon. 1, 97–105 (2007).

Source: Nature Physics.

The team incorporated semiconducting materials in critical regions of tiny elements – in this case metallic split-ring resonators – that interact with light in order to tune metamaterials beyond their fixed point on the electromagnetic spectrum, an advance that opens these novel devices to a broader array of uses, according to findings published in the online version of the journal Nature Photonics.

“Metamaterials no longer need to be constructed only out of metallic components,” said Boston College Physicist Willie J. Padilla, the project leader. “What we’ve shown is that one can take the exotic properties of metamaterials and combine them with the unique prosperities of natural materials to form a hybrid that yields superior performance.”

Padilla and BC graduate student David Shrekenhamer, along with Hou-Tong Chen, John F. O’Hara, Abul K. Azad and Antoinette J. Taylor of Los Alamos National Laboratory, and Boston University’s Richard D. Averitt assembled a single layer of metamaterial and semiconductor that allowed the team to tune terahertz resonance across a range of frequencies in the far-infrared spectrum.

The team’s first-generation device achieved 20 percent tuning of the terahertz resonance to lower frequencies – those in the far-infrared region –addressing the critical issue of narrow band response typical of all metamaterial designs to date.

Constructed on the micron-scale, metamaterials are composites that use unique metallic contours in order to produce responses to light waves, giving each metamaterial its own unique properties beyond the elements of the actual materials in use.

Within the past decade, researchers have sought ways to significantly expand the range of material responses to waves of electromagnetic radiation – classified by increasing frequency as radio waves, microwaves, terahertz radiation, infrared radiation, visible light, ultraviolet radiation, X-rays and gamma rays. Numerous novel effects have been demonstrated that defy accepted electromagnetic principles.

“Metamaterials demonstrated negative refractive index and up until that point the commonly held belief was that only a positive index was possible,” said Padilla. “Metamaterials gave us access to new regimes of electromagnetic response that you could not get from normal materials.”

Prior research has shown that because they rely on light-driven resonance, metamaterials experience frequency dispersion and narrow bandwidth operation where the centre frequency is fixed based on the geometry and dimensions of the elements comprising the metamaterial composite. The team believes that the creation of a material that addresses the narrow bandwidth limitations can advance the use of metamaterials.

Enormous efforts have focused on the search for materials that could respond to terahertz radiation, a scientific quest to find the building blocks for devices that could take advantage of the frequency for imaging and other applications.

Potential applications could lie in medical imaging or security screening, said Padilla. Materials undetectable through x-ray scans – such as chemicals, biological agents, and certain explosives – can provide a unique “fingerprint” when struck by radiation in the far-infrared spectrum. Metamaterials like the one developed by the research team will facilitate future devices operating at the terahertz frequency.

In addition to imaging and screening, researchers and high-tech companies are probing the use of terahertz in switches, modulators, lenses, detectors, high bit-rate communications, secure communications, the detection of chemical and biological agents, and characterization of explosives, according to Los Alamos National Laboratory.

Links:

Nature Photonics Article

Source: Boston College & PhysOrg.com

The NIST terahertz imaging system reveals slight temperature differences, as shown in this post-processed image. The color scale ranges from blue indicating 301 K or 28.75 degrees C, to red indicating 302.5 K or 29.35 degrees C. The image was made of the test scene shown in the photo, a room-temperature ring on top of a warmer absorber material. Quantitative analysis shows the current system can distinguish structures with dimensions as small as 4 millimeters, to be significantly improved in the future. Credit: NIST

Terahertz radiation falls between microwaves and infrared radiation on the electromagnetic spectrum, with frequencies from about 300 million cycles per second to about 3 trillion cycles per second. Biological and chemical samples naturally emit characteristic signatures of terahertz radiation, but detecting and measuring them is a unique challenge because the signals are weak and absorbed rapidly by the atmosphere.

The NIST prototype imager, described in detail for the first time in a new paper, uses an exquisitely sensitive superconducting detector combined with microelectronics and optics technologies to operate in the terahertz range. The NIST system has its best resolution centered around a frequency of 850 gigahertz, a “transmission window” where terahertz signals can pass through the atmosphere. The system can detect temperature differences smaller than half a degree Celsius, which helps to differentiate between, for example, tumors and healthy tissue.

The heart of the system is a tiny device that measures incoming terahertz radiation by mixing it with a stable internal terahertz signal. This mixing occurs in a thin-film superconductor, which changes temperature upon the arrival of even a minute amount of radiation energy. The slight frequency difference between the two original terahertz signals produces a more easily detected microwave frequency signal.

NIST developed the device and antenna, combined with an amplifier on a chip smaller than a penny, in collaboration with the University of Massachusetts. Called a hot electon bolometer (HEB), the technology is sensitive enough to detect the weak terahertz signals naturally emitted by samples, eliminating the need to generate terahertz radiation to actively illuminate the samples. This greatly reduces complexity and minimizes safety concerns. In addition, the NIST “mixer” system delivers more information by detecting both the magnitude and phase (the point where each individual wave begins) of the radiation.

Because passively emitted signals are so weak, the current system takes about 20 minutes to make a single 40 x 40 pixel image. NIST researchers are working on an improved version that will scan faster and operate at two frequencies at once. Future systems also should be able to achieve better spatial resolution.

Citation: E. Gerecht, D. Gu, L. You and S. Yngvesson. Passive heterodyne hot electron bolometer imager operating at 850 GHz. Forthcoming in IEEE Transactions on Microwave Theory and Techniques.

Source: National Institute of Standards and Technology and PhysOrg.com

“We have taken a first step to making circuits that can harness or guide terahertz radiation,” says Ajay Nahata, study leader and associate professor of electrical and computer engineering. “Eventually—in a minimum of 10 years—this will allow the development of superfast circuits, computers and communications.”

Electricity is carried through metal wires. Light used for communication is transmitted through fiberoptic cables and split into different colors or “channels” of information using devices called waveguides. In a study to be published Friday, April 18 in the online journal Optics Express, Nahata and colleagues report they designed stainless steel foil sheets with patterns of perforations that successfully served as wire-like waveguides to transmit, bend, split or combine terahertz radiation.

“A waveguide is something that allows you to transport electromagnetic radiation from one point to another point, or distribute it across a circuit,” Nahata says.

If terahertz radiation is to be used in computing and communication, it not only must be transmitted from one device to another, “but you have to process it,” he adds. “This is where terahertz circuits are important. The long-term goal is to develop capabilities to create circuits that run faster than modern-day electronic circuits so we can have faster computers and faster data transfer via the Internet.”

Nahata conducted the study with two doctoral students in electrical and computer engineering: Wenqi Zhu and Amit Agrawal.

Developing terahertz technology

The electromagnetic spectrum, which ranges from high to low frequencies (or short to long wavelengths), includes: gamma rays, x-rays, ultraviolet light, visible light (violet, blue, green, yellow, orange and red), infrared light (including radiant heat and terahertz radiation), microwaves, FM radio waves, television, short wave and AM radio.

Fiber optic phone and data lines now use near-infrared light and some visible light. The only part of the spectrum not now used for communications or other practical purposes is terahertz-frequency or far-infrared radiation—also nicknamed T-rays—located on the spectrum between mid-infrared and microwaves.

With so much of the spectrum clogged by existing communications, engineers would like to harness terahertz frequencies for communication, much faster computing and even for anti-terrorism scanners and sensors able to detect biological, chemical or other weapons. Nahata says the new study is relevant mainly to computers that would use terahertz radiation to run at speeds much faster than current computers.

In March 2007, Nahata, Agrawal and others published a study in the journal Nature showing it was possible to control a signal of terahertz radiation using thin stainless steel foils perforated with round holes arranged in semi-regular patterns.

This February, British researchers reported they used computer simulations and some experiments to show that indentations punched across an entire sheet of copper-clad polymer could hold terahertz radiation close to the sheet’s surface. That led them to conclude the far-infrared light could be guided along such a material’s surface.

But the London researchers did not actually manipulate the direction the terahertz radiation moved, such as by bending or splitting it.

“We have demonstrated the ability to do this, which is a necessary requirement for making terahertz guided-wave circuits,” Nahata says.

Circuits: from electrical to optical to terahertz

Wires act as waveguides for electricity. Wires connect active devices such as transistors, which switch or adjust the electric signal. That is the basis for how computers work today. An electronic integrated circuit is a computer processor made of wires, transistors, resistors and capacitors on a semiconductor chip made of silicon.

In optical communications, the waveguides carry laser-generated light in fiber optic cables and lines etched or deposited on an insulator or semiconductor surface. Nahata says photonic integrated circuits now are used for phone and Internet communications, mainly for combining or “multiplexing” different colors or channels of light entering a fiber-optic cable and separating or “demultiplexing” the different wavelengths exiting the cable.

“Electronic circuits today work at gigahertz frequencies—billions of cycles per second. Electronic devices like a computer chip can operate at gigahertz,” Nahata says. “What people would like to do is develop capabilities to transport and manipulate data at terahertz frequencies [trillions of hertz.] It’s a speed issue. People want to be able to transfer data at higher speeds. People would like to download a movie in a few seconds.”

“In this study, we’ve demonstrated the first step toward making circuits that use terahertz radiation and ultimately might work at terahertz speeds,” or a thousand times faster than today’s gigahertz-speed computers, Nahata says.

Channeling, bending, splitting and coupling T-tays

“People have been working on terahertz waveguides for a decade,” he says. “We’ve shown how to make these waveguides on a flat surface so that you can make circuits just like electronic circuits on silicon chips.”

The researchers used pieces of stainless steel foil about 4 inches long, 1 inch wide and 625 μm thick, or 6.25 times the thickness of a human hair. They perforated the metal with rectangular holes, each measuring 500 μm (five human hair widths) by 50 μm (a half a hair width). The rectangular holes were arranged side by side in three different patterns to form “wires” for terahertz radiation:

* One line of rectangles that served as a “wire” and carried terahertz radiation.
* A line that becomes two lines—like the letter Y—to split the far-infrared light, similar to a splitter used to route a home cable TV signal to separate television sets.
* Two lines that curve close to each other in the middle—like an X where the two lines come close but don’t touch—so the radiation could be “coupled,” or moved from one line or “wire” to another.

The straight pattern successfully carried terahertz radiation in a straight line. The other two patterns “changed the direction the terahertz radiation was moving” by splitting it or coupling it, Nahata says. The study showed the terahertz radiation was closely confined both vertically (within 1.69 mm of the foil’s surface) and horizontally (within 2 mm of the pattern of rectangles as it moved over them).

“All we’ve done is made the wires” for terahertz circuits, Nahata says. “Now the issue is how do we make devices [such as switches, transistors and modulators] at terahertz frequencies”

When terahertz radiation is fed into the stainless steel waveguides, it spans a range of frequencies. One frequency is guided across the steel surface. That frequency is determined by the size of perforations in the foil. The engineers chose a frequency they could generate and measure: about 0.3 Thz, or 300 GHz. Terahertz radiation is defined as ranging from 0.1 THz (or 100 GHz) to 10 THz.

The design of the waveguide means that it carries terahertz radiation in the form of surface plasma waves—also known as plasmons or plasmon polaritons—which are analogous to electrons in electrical devices or photons of light in optical devices. The surface plasma waves are waves of electromagnetic radiation at a terahertz frequency that are bound to the surface of the steel foil because they are interacting with moving electrons in the metal, Nahata says.

Source: Univ. of Utah, and R&D

TST accepts English manuscript ONLY, submitted in BOTH .PDF and .DOC format. As a free quarterly international journal (free submission, publication and downloading) so far, TST covers the major topics of THz academic research, novel devices and applications in various areas and so on. TST aims at building up a global platform for THz experts and researchers to have a better academic cc-operation and information exchanges.

TST sincerely invites manuscripts from THz experts and researchers all over the world.

Submission Email : tst@tstnetwork.org.

More Information: www.tstnetwork.org.

The terahertz regime lies between the far-infrared and microwave regions of the electromagnetic spectrum, between about 300 GHz to 10 THz. Such long-wave radiation is valued for its ability to penetrate objects that are opaque at visible and infrared frequencies, with the result that terahertz waves are becoming increasingly popular for imaging and spectroscopy applications.

Unfortunately, it has proved difficult to generate intense radiation in this regime because terahertz waves are too long for direct optical techniques but too short for electronic devices. Various indirect methods are now in use, such as firing a powerful laser beam at a nonlinear optical material, but these offer limited output powers.

Researchers have also experimented with producing terahertz radiation from synchrotron sources, where the nonlinear behaviour of relativistic electrons has been shown to generate coherent terahertz emission with an average power level of several tens of watts. These experiments have so far only produced broadband emission, but the French/Japanese team have now demonstrated that a laser-based technique can produce narrowband emission that can be tuned over a range of frequencies (Nature Physics doi:10.1038/nphys916).

“The set-up of spectroscopy studies is simpler with narrowband sources than with broadband emission, while the combination of narrowband, tunable and high-power emission offers some important advantages.” Serge Bielawski of the Lille University for Science and Technology told optics.org. “When it is used a pump light, one can selectively excite a particular molecular excitation mode. When it is used as a probe light, there is no need for filters and so there is no degradation in intensity.”

Synchrotron scheme
In the new scheme, a pulse from an 800 nm Ti:Sapphire laser is first sinusoidally modulated with a period in the picosecond range. This modulated pulse is then made to interact with an electron bunch produced by the UVSOR-II storage ring in Okazaki, Japan, which operates at 600 MeV and has a circumference of 53 m.

The effect of the laser pulse is to create a modulation in the energy distribution of the electrons. In the first stage of the experiment, the laser–electron interaction occurs in a periodic magnetic field that is tuned to the laser wavelength, which modulates the energy distribution of the electrons on the optical scale. Passing the electrons through a bending magnet then induces the charge-density modulation that is necessary for obtaining coherent terahertz emission.

“To achieve narrowband terahertz emission, the key point is that the emitted spectrum is the Fourier transform of the longitudinal charge density modulation,” explained Bielawski. “That’s why we decided to create laser pulses with a longitudinally sinusoidal modulation.”

The frequency of emission can be varied by simply adjusting the delay in a Michelson interferometer. In this experiment, the emission could be tuned between about 0.2 and 1.0 THz, the the team plan to redo the experiment at higher frequencies by using another beamline and different beam parameters. According to Bielawski, implementing the scheme on more advanced synchrotron sources would extend the tunability range to the multi-THz regime.

Route to hugher energies
The experiments revealed strong tunable terahertz emission when the laser pulse was modulated with a period of 1-2 ps. Terahertz pulses were produced with energies of a few nanojoules and a brilliance in the nJ/cm range – which is comparable to the performance of commercial terahertz sources – but Bielawski says that straightforward improvements to the optics would yield much better figures.

“The present feasibility study will be followed by a research programme to optimize the terahertz emission,” he said. “Increases by orders of magnitude are expected to be obtained by elementary optimizations of overlap, incident power and current density in the storage ring.”

One simple improvement will be to increase the energy of the incident laser pulses from about 150 µJ in the current work to 10–20 mJ. Experiments in more powerful synchrotron sources are also planned. According to Bielawski, the technique could also be used to probe the instabilities that emerge in electron bunches, which often leads to spontaneous bursts of terahertz emission. “We are interested in trying to ’seed’ these instabilities using modulated pulses, which would increase the amount of terahertz produced,” he said.

Source: Optics.org

Rome, April 9 - Italy is leading a European Union drive to produce medical and security scanning waves that could be a better and safer alternative to X-rays.

‘’T-waves could take over some of the jobs currently done by X-rays - but could do them more safely and more effectively,'’ Professor Aldo Di Carlo of Rome’s Tor Vergata University said. Di Carlo has kickstarted a four-year, four-million-euro EU project to boost the availability of Terahertz or T-waves.

‘’Up till now it has been very hard to get enough of these waves,'’ he said. There are currently only a handful of available T-wave sources, he noted, such as devices called Quantum Cascade Lasers (QCLs).

The Tor Vergata-led scheme aims to build a new machine to enhance these sources.

With the help of some of Italy’s top hi-tech firms, it aims to create a special booster called a Vacuum THz Amplifier.

New techniques such as ‘micromachining’ and nanotechnologies will be used to build the amplifier, Di Carlo said.

Once obtained, the waves could be used in many fields ranging from medicine to security, Di Carlo said.

With a spectrum between the microwaves used in cellphones and the infra-red waves in fiber-optic broadband cables, T-rays aren’t strong enough to pose health risks.

They could thus be a safe alternative to X-rays in identifying diseases like cancer, Di Carlo said.

‘’The great thing is that T-rays, unlike X-rays, aren’t sufficiently powerful to damage body tissue'’.

‘’They should be able to identify any anomalies earlier,'’ he added.

T-rays also have ‘’impressive'’ potential in the security field, the professor said. ‘’They can penetrate materials such as plastic, cardboard and paper and reveal concealed weapons and dangerous substances like drugs or explosive.

‘’Because they don’t pose the health risks that X-rays do, they could be used in crowded areas such as airport lobbies and not just in specific scanner sites'’. Di Carlo said THz radiation also had potential uses in space, biology and microscopy. Di Carlo’s OPTHER (Optically Driven Terahertz Amplifiers) project sets out ‘’to give Europe a top role in the field,'’ according to its website, www.opther.eu.

The OPTHER consortium brings together six partners.

Tor Vergata is working with the Technical University of Denmark and the French National Research Council.

It has three industrial partners, THALES Research & Technology and THALES Electron Devices from France, and SELEX-SI from Italy.

Experts at the Hebrew University of Jerusalem say that the shape of sweat ducts, the tiny tubes that connect sweat glands to the outside of the skin, is similar to that of some antennas.

According to them, the wavelength at which human sweat glands interact falls in the sub-terahertz (T-ray) range, which has recently been used in a variety of other applications, from uncovering hidden artwork to finding concealed weapons.

While sweating does not produce T-rays, sweat production changes the wavelength that is bounced back off the sweat duct antenna.

Designing a machine capable enough to measure these wavelengths, surmise the researchers, it may be calculated how much and where a person is sweating.

The researchers have also shown that monitoring the kinds of sweating based on where a person is sweating - such as on the forehead or on the chest and back - may make it possible to measure blood pressure and pulse rate remotely.

Currently, the only way to measure blood pressure is by using an inflatable pressure cuff or a surgically implanted monitor, and the only way to measure sweat is through a cumbersome process that uses electrodes on a small portion of skin.

The researchers say that the new method can do both remotely and constantly.

“This could open up a whole new area of research,” Discovery News quoted James Wolff, a doctor at Emerson Hospital in Concord, Massachusetts, who was not associated with the study.

As to how useful such a system can be for conducting lie detection tests, the researchers said that trained professionals could evade polygraphs made on the basis of their physiological responses like faster pulse, higher blood pressure, and increased sweating; however, if a person does not know they are being constantly tested, the new method could be more effective.

Jonathan Marks, a professor of bioethics at Pennsylvania State University, said that lie detection using this method would still have problems with accuracy, as a people anxious over something else at the time of tests could trigger a false positive.

“There are concerns about people’s privacy. Is there a justification for screening people en masse for physiological data? Where would you do this?” said Marks.

Source: NewKerala

Radio sweat gland — 90 GHz

The perils of perspiration

Sweat ducts in human skin act like an array of tiny antennas that pick up radiation at specific frequencies, according to researchers. The finding might one day be used in medical and security technologies to assess a person’s mental state from a distance.

A team of researchers in Israel has shown that sweat ducts pick up radiation at frequencies of about 100 gigahertz — the so-called extremely high frequency or EHF range, lying between microwaves and terahertz radiation. The antenna behaviour is all down to the ducts’ curious shape: they thread through the epidermis as regular helices. Filled with electrically conductive sweat, these channels act rather like coils of wire that absorb radiation across the millimetre and sub-millimetre wavelength band.

Yuri Feldman of the Hebrew University of Jerusalem and his colleagues directed a beam of EHF radiation onto the skin of the palms of subjects who had been jogging for 20 minutes, and measured the radiation that was reflected back. They found a strong band of absorption that was not seen before exercise. This absorption gradually disappeared as the subjects rested after jogging (Y. Feldman et al. Phys. Rev. Lett. 100, 128102; 2008). The researchers also found that the reflection signals were proportional to blood pressure and pulse rate — known indicators of physiological stress leading to sweating.

And when the researchers suppressed palm sweating with a synthetic compound that mimics the paralysis of snake venom, inactivating the sweat glands, they found that EHF absorption during exercise was markedly reduced.

The helical antenna array makes skin a kind of biological metamaterial, Feldman’s group says, in which the material’s response to electromagnetic radiation is determined by structure rather than composition. Metamaterials made from arrays of tiny electrical circuits are being explored for applications ranging from super-lenses to invisibility shields. “Nature has done what is being attempted extensively today in nanophotonics,” Feldman says. “This effect might be used for biomedical and homeland-security applications.”

Sweating hands have been used in lie detection, but using physiological parameters in ‘polygraph’ lie detectors is controversial and was strongly criticized in a 2002 report by the US National Academy of Sciences. “Perspiration is related to increases in emotional arousal,” says Paul Ekman, a psychologist in Oakland, California, and an author of the academy’s report. But he adds that “it can be the consequence of many different mental processes” — not only lying.

So far, Feldman and his colleagues are cautious about whether the idea will work at all, let alone how it might be applied. For example, they need to find the distance at which a meaningful signal can be detected and how long it takes for the signal to register changes in the biometric parameters. “We are just starting our journey in these uncharted waters,” says Feldman.

Source: Nature News

Durham Photonics, developers of advanced imaging software in biomedicine and bioscience, says the £95,000 grant, awarded by One NorthEast, will enable it to recruit a full-time scientific team as well as to begin feasibility studies on imaging systems.

A University of Durham spin-out, Durham Photonics was established in June 2007 and is based in the university’s laboratories and Enterprise Incubator.

Its first product, a terahertz microscope, will be the first of its kind to reach market and is able to help scientists analyse cells to help separate healthy from unhealthy ones.

This will have help scientists in the field of biomedicine, nanomedicine and nanotechnology and assist in the fight against cancer.

The terhaertz microscope does not cause damage when examining cells, unlike the normal X-ray, and therefore has great potential to look at living things.

Dr Amanda McMurray, managing director at Durham Photonics said: “This grant will enable us to further our development through additional research and to recruit new expertise. This is the first microscope of its kind in the world and we expect to be able to bring it to market within a few years.”

Durham Photonics eventually hope to establish a manufacturing facility here in the North East employing up to 30 people.

Dr McMurray added: “Cenamps has supported the company since foundation and we continue to benefit from their input as well as that of other stakeholders. Outside investment remains imperative if we are to continue to excel in such an innovative field.”

Durham Photonics has benefited from Cenamps’ BioNano Regional Research Programme, which funded research in the Photonics Materials Institute that underpinned the terahertz microscope. The programme, run by Cenamps and funded by One NorthEast, aimed to accelerate the development and exploitation of cutting edge ideas.

Everybody knows microwaves – but what are terahertz waves? These higher-frequency waves are a real jack-of-all-trades. They can help to detect explosives or drugs without having to open a suitcase or search through items of clothing. They can reveal which substances are flowing through plastic tubes. Doctors even hope that these waves will enable them to identify skin cancer without having to perform a biopsy.

In the electromagnetic spectrum, terahertz waves are to be found between infrared radiation and microwaves. They can penetrate wood, ceramics, paper, plastic or fabrics and are not harmful to humans. On the other hand, they cannot pass through metal. This makes them a universal tool: They change when passing through gases, solid materials or liquids. Each substance leaves its specific fingerprint, be it explosives or water, heroin or blood.

So far, however, the technology has not made a breakthrough, as it is expensive and time-consuming to build the required transmitters and receivers. Now researchers at the Fraunhofer Institute for Physical Measurement Techniques IPM are making the devices mobile. To generate terahertz waves, the scientists use a femtosecond laser which emits extremely short flashes of infrared light. To illustrate: In one femtosecond, a ray of light moves forward by about the width of a hair. The pulsed light is directed at a semiconductor, where it excites electrons which then emit terahertz waves. In conventional equipment, the laser light moves freely through the room, which makes measurement inflexible and susceptible to vibrations.

The Fraunhofer experts have taken a different approach, guiding the light through a glass fiber of a type similar to that used for transmitting data. “Our fiber-based system is so robust that we can simply plug it into a standard 240-volt socket,” says IPM expert Joachim Jonuscheit. This is not the only benefit: Until now the equipment has required a shock-proof base so that measurements are not falsified by vibrations. With the beam path inside a glass fiber, this is no longer necessary.

The advantages are obvious: The transmitters and receivers, which are about the size of beverage cans, are now attached to a flexible cable and can be positioned wherever desired. Since vibrations are no longer a problem, the device can even be deployed on the factory floor with fork-lift trucks driving around and heavy machinery vibrating. No inspection point is too difficult to access, as the glass fiber cables can bridge distances up to 25 meters.

Source: PhysOrg.com

Linfield claims that his team has created the highest operating temperature for a terahertz quantum cascade laser. That may sound strange, but makes sense if you consider the fact that these lasers only work at temperatures of minus 100° Celsius. A room-temperature laser is still science fiction, but the scientists said they have found a way to increase “the laser’s operating temperature by nearly ten degrees”.

“The potential uses for terahertz technology are huge, but at the moment they are limited to niche applications in, for example, the pharmaceutical industry and astronomy, as the current systems on the market are expensive and physically quite large. The availability of cheap, compact systems would open up a wide range of opportunities in fields including industrial process monitoring, atmospheric science, and medicine,” Linfield said.

Source: TG Daily

The research, carried out in collaboration with the group of Professor Frederico Capasso at Harvard University, and supported by the Engineering and Physical Sciences Research Council (EPSRC) is published in Optics Express ( Vol. 16, Issue 5, pp. 3242-3248).

However, thus far it has been extremely difficult here to produce and transmit enough transmitting power.

That could change now. Engineers and physicists of the Terahertz Communications Lab in Braunschweig, a cooperation of the Physikalisch-Technische Bundesanstalt (PTB) and the Technische Universität Braunschweig, have now - worldwide for the first time - successfully transmitted a video signal at a frequency of 300 GHz, over a distance of more than 22 meters, and have thus demonstrated that the transmission of user data is possible with terahertz waves.

Terahertz radiation is generally non-ionizing, and is also not expected to damage tissues and DNA - an issue which may make it more acceptable to people who are concerned about radiation and health effects.

Source: Cellular News.

“We are developing a revolutionary process that will enable large-scale production of 1µm to 5µm, single-crystal, thin-film pyroelectric detectors,” said Sri Sriram, president of SRICO. “We anticipate an order of magnitude increase in detector performance over the current technology,” In addition, these devices will operate at room temperature, a major improvement over conventional high-sensitivity sensor solutions, like microbolometers, that typically require bulky, costly cryogenic cooling systems. “Room-temperature operation is critical,” Sriram continued. “Not only does it provide greater design flexibility, it helps open the door to a full range of portable THz applications, from medical instrumentation to bomb-detection devices.”

Spectrum Detector will focus its efforts on manufacturability. “What we bring to the table is the know-how to make these devices cost effective and easy to produce – while maintaining the utmost in quality and performance,” said Don Dooley, president of Spectrum Detector. “In today’s market, the most advanced thin-film detectors one can specify are typically 25µm thick– and these have to be hand crafted, one by one. In contrast, we anticipate our new manufacturing processes will allow semi-automated fabrication of up to 100 devices per substrate – even when fabricating devices as thin as 1µm to 5µm.”

The T5000 camera, created by a company called ThruVision, uses what it calls “passive imaging technology” to identify objects by the natural electromagnetic rays–known as Terahertz or T-rays–that they emit.

The high-powered camera can detect hidden objects from up to 80 feet away and is effective even when people are moving. It does not reveal physical body details and the screening is harmless, the company says.

The technology, which has military and civilian applications and could be used in crowded airports, shopping malls or sporting events, will be unveiled at a scientific development exhibition sponsored by Britain’s Home Office on Wednesday and Thursday.

“Acts of terrorism have shaken the world in recent years and security precautions have been tightened globally,” said Clive Beattie, the chief executive of ThruVision. “The ability to see both metallic and nonmetallic items on people out to 25 meters is certainly a key capability that will enhance any comprehensive security system.”

While the technology may enhance detection, it may also increase concerns that Britain is becoming a surveillance society, with hundreds of thousands of closed-circuit television cameras already monitoring people countrywide every day.

ThruVision came up with the technology for the T5000 in collaboration with the European Space Agency and from studying research by astronomers into dying stars.

The technology works on the basis that all people and objects emit low levels of electromagnetic radiation. Terahertz rays lie somewhere between infrared and microwaves on the electromagnetic spectrum and travel through clouds and walls.

Depending on the material, the signature of the wave is different, so that explosives can be distinguished from a block of clay and cocaine is different from a bag of flour.

Source: Reuters via News.com.

Also see CBS News story on this camera, including a video report.

Harmless electromagnetic radiation beams could replace X-rays at airport security posts, enabling passengers to pass inspection quickly without shedding shoes, belts and pocket change.

T-rays, or terahertz radiation, penetrate clothing and some other materials but they don’t go through metals or travel deeply inside the human body. While X-rays work by penetrating human tissue and other materials, creating images, T-rays create molecular “fingerprints” of materials they encounter. In theory T-rays should identify explosives carried in a piece of luggage.

And T-rays, like radio waves and visible light, pose no human health risk because they don’t ionize materials they encounter, as X-rays do.

Scientists use T-rays in research, but they have been limited mostly to laboratory settings because there has been no way to generate them cheaply. A research team at Argonne National Laboratory recently raised hopes for commercial applications by successfully generating T-rays from tiny crystals of high-temperature superconductors.

“There’s been a race,” said Ken Gray, an Argonne scientist. Large groups of T-ray researchers in Japan and Germany were astonished in October when they learned of Argonne’s success, Gray said.

Although only a tiny speck barely large enough to see, the layered crystal Argonne scientists used to generate T-rays is much larger than what their international competitors were using, said Wai-Kwong Kwok, another member of the Argonne team.

“The prediction was that you wouldn’t get T-ray emissions from larger crystals,” Kwok said. “We looked at the theories and wondered why was it not working?”

The key to their success, said Ulrich Welp of Argonne’s materials science team, is tiny cavities in the crystals that generate T-rays when weak alternating electric current passes through them. The scientists shaped and arranged the cavities so the oscillations generated by the current would synchronize and amplify one another.

“That’s been the challenge all along,” Welp said. “If one junction oscillates up while another junction oscillates down, they’ll cancel each other out and you won’t get anything.”

Their discovery drew interest from commercial firms and the Department of Defense, said Welp. Besides raising T-ray output, the team needs to find a way to tune the rays to different terahertz frequencies, giving them the ability to identify a variety of materials.

Potential commercial partners and the military “would like a demonstration. They’d like us to identify explosives,” said Gray. “We’re not there yet, but we’re exploring several avenues to get us there.”

If the researchers can show that T-rays identify explosives and attract hoped-for federal grants and private investment, the technology could be ready for commercialization in three to five years, Welp said.

The Argonne researchers have applied for a patent on their discovery and are working to improve the device’s efficiency. The scientists know they are getting only a fraction of the potential T-ray energy the crystal can produce.

Using T-rays at airport security stations raises some privacy issues for people concerned that the technology might be used to look through a person’s clothing, undressing them visually, but Gray said that is not easily done.

“Your imagination does a much better job,” he said.

More likely the equipment would use T-rays to feed information into a computer for analysis. Most passengers would pass through an inspection quickly and a few would be singled out by the computer for closer inspection by a human. Such inspections could be triggered, for example, if a tube of toothpaste a passenger carried had a molecular fingerprint similar to an explosive’s.

Metal detectors and X-ray machines along with humans looking at images of every piece of luggage in search of suspicious materials would be phased out if T-rays can meet their potential.

Costs are difficult to estimate so early in the process, but the scientists said T-ray-based technology would cost less than today’s X-ray-based equipment because the underlying solid-state technology is cheaper to produce.

If they can be generated as cheaply as the Argonne researchers predict, T-rays would probably be applied to products beyond security systems. They might be used to diagnose certain kinds of skin cancer and used in dental offices to identify tooth decay, replacing X-rays in some cases.

———-

jvan@tribune.com

- - -

About T-rays, terahertz radiation

- T-rays are a safe form of electromagnetic radiation. They do not have sufficient energy to cause cellular damage that can lead to cancer.

- The rays do not penetrate through metal but do penetrate materials such as leather, fabric and paper.

- Unlike X-rays, T-rays should be able to identify a wider range of hazardous materials, such as explosives and illegal substances.

Source: The Chicago Tribune.

The DOTFIVE project, which is being led by STMicroelectronics, hopes to develop the devices needed for future millimeter wave and terahertz communication, radar, imaging and sensing applications.

The three year DOTFIVE project is worth €14.75million, with €9.7m coming from the EC. This makes it the largest ‘More than Moore’ nanoelectronics project running within the EU’s Framework Programme 7.

DOTFIVE is aiming to establish a leadership position for the European semiconductor industry in the area of SiGe heterojunction bipolar transistors (HBTs) for millimeter wave applications. “With this ambitious project,” said Gilles Thomas, DOTFIVE project coordinator and STMicroelectronics R&D Cooperative Programs Manager, “Europe is getting ahead of the rf roadmap defined in ITRS, strengthening its position in an area where the whole ecosystem is already strong.”

Emerging high volume millimeter wave applications include 77GHz automotive radar applications and 60GHz wireless lan systems. In addition to these evolving markets, DOTFIVE technology sets out to be a key enabler for imaging systems with applications in the security, medical and scientific sectors.

Current SiGe HBTs have a maximum operating frequency of 300GHz at room temperature. DOTFIVE is looking to boost this to 500GHz, previously thought to require III-V compound semiconductors.

The project involves 15 partners from industry and academia in five countries. Infineon and STMicroelectronics are joined by research institutes IMEC and IHP. Meanwhile, XMOD Technologies and GWT-TUD will provide parameter extraction and rf device modeling expertise. Academic partners include the Johannes Kepler University of Linz, ENSEIRB, Paris-Sud University, Technical University of Dresden, Bundeswehr University, University of Siegen and the University of Naples.

Source: New Electronics.

More about DOTFIVE.

The “Clear Prize” was announced by Clear, of New York, US – a firm that already offers quicker checkpoint services at airports for a fee.

“We’re looking at moving things that are conceptual or in the lab to things that we can deploy,” says company CTO Jason Slibeck.

The cash prize will go to any individual, company or institution that can get customers through airport security 15% faster, at a cost of less than 25 cents per passenger, using technology or processes that will be approved by the Transportation Security Administration (TSA). If passengers do not need to remove their clothes or shoes, for example, it could speed up processing significantly.

Technology boost

Slibeck says that over 150 individuals, start-ups, defense contractors and universities have shown an interest in the prize, which was announced on 13 February. Novel screening technologies seem likely to emerge as key to faster processing, he adds.

One promising procedure is mass spectroscopy, which involves analysing the mass-charge ratio of ions on a swab sample taken from a passenger’s clothing or air collected from around them. The method can quickly spot traces of substances including explosives or drugs.

Another is terahertz scanning – passing low-energy electromagnetic waves through passengers and their clothing or by detecting differences in electromagnetic waves naturally emitted by the body and by concealed objects. By getting passengers to walk through a series of cameras that detect terahertz waves security agents can quickly tell whether they are concealing anything beneath their clothes.

Hidden cash

“If there is something disrupting the emissions, we see it,” says Gary Tryon of Brijot Imaging Systems, one of several companies to have developed such detection technology. Tryon says the technology can quickly spot plastics, glass, narcotics, explosives and even wads of cash hidden beneath clothing.

In December 2007, the company was awarded a contract worth more than $2 million by the UK government to install its electromagnetic detection systems at several UK airports and ports.

Tryon thinks the company could develop a screening process that would meet the requirements of Clear Prize, but says gaining TSA approval could be the hardest part for entrants. “It’s one thing to have a product that works,” Tyron says. “It’s another to get approval from government agencies.”

Source: New Scientist.

In the framework of the Agreement between the Government of Italy and the Government of Japan on cooperation in Science and Technology in the years 2008-2009, the Joint Committee of the Delegations of Japan and Italy selected eighteen significant bilateral projects in the priority areas of Basic Sciences (Physics, Chemistry, Mathematics, Biology), Life Sciences (including Health, Biotechnology, Agriculture), Space, Earth Science and Climate change, Energy, Information and Communication Technology, Robotics and Production Technologies, Nanosciences, Advanced Materials, Technologies applied to Cultural Heritage.

The project THz-ARTE “Terahertz Advanced Research TEchniques for non-invasive analysis in art conservation” jointly coordinated by the Department of Physical Technologies and New Materials at ENEAFrascati (Dr. Gian Piero Gallerano) and by the National Institute of Information and Communication Technology – Tokyo (Dr. Kaori Fukunaga), has been selected in the area of Technologies applied to Cultural Heritage.

The main objective of THz-ARTE is the demonstration of terahertz spectroscopy and reflective terahertz imaging as new non-destructive analysis tools of art objects, including paintings, murals, coloured or varnished sculpture and coloured furniture.

The project is addressing in particular:
- The comparison of different spectroscopic techniques in various frequency ranges from the near IR to the microwave region and the setup of a THz database for art materials;
- The investigation of hidden, stratified and plaster covered paintings by reflective THz imaging techniques that may lead to the identification of original layers;
- Research on ageing mechanism of art materials and proposals on accelerated ageing test of new materials for conservation.

The Japanese group at NICT has firstly applied THz spectroscopy to art analysis and has developed an open database of art materials with Tohoku University and RIKEN [see IEICE Electronic Express, 4 (2007) 258-263 and Researchers develop new method to expose art forgeries].

The ENEA-Frascati team has a long standing expertise in the development of THz sources, detectors and instrumentation. ENEA-Frascati operates two compact Free Electron Laser sources covering the spectral range from 90 to 150 GHz and from 0.4 to 0.7 THz respectively. The ENEA team is employing these sources together with far infrared gas lasers and solid state oscillators to perform reflective THz imaging on a variety of samples in the biological, environmental and art conservation fields with sub-wavelength resolution [Proceedings of the IEEE - 95, No. 8 (2007) 1666-1678].

The collaboration is strengthened by the participation of Ing. Maurizio Seracini of Editech, Florence, a scientist with over 30 years expertise in the field of non-invasive diagnostics of fine arts, who will contribute with the preparation of samples and with the choice of sites for on-field measurements.

Preliminary measurements on non-invasive diagnostics for multilayered art objects have been conducted at ENEA-Frascati in collaboration with NICT utilizing a reflective imaging set-up at 150
GHz capable of characterising small area (5 x 5 cm²) samples with 0.2 mm spatial resolution [Proc. of the IRMMW-THz2005, art.no. 1572505 (2005) 255-256].

Results on the imaging of painting covered by gesso have been reported at the “Workshop on Infrared spectroscopy and microscopy” WIRMS-2007 held at Awaji Island – Japan in September 2007.

“We have created a metamaterial that guides terahertz radiation close to the surface in a surface wave,” researcher Dr Stephan Maier said.

Visible light can already be trapped as surface plasmon polaritons (SSPs) on a surface because, said Maier, the plasmon frequency of gold, silver and copper is similar the frequency of visible light. He added that radio ground waves sticking to the Earth’s surface as Sommerfeld waves are SSPs on a grand scale.

“Red light at 600nm is trapped within 100 to 200nm of a gold surface enabling you to manipulate it,” he said. “Metals are easy to process and have low losses, so it would be very nice to do this with THz radiation and even microwaves.”

Working with the Universities of Bath, Madrid, and Zaragoza, the Imperial team has perforated a metal surface with rectangular pits to create the metamaterial with a suitable plasmon frequency to trap 1THz radiation. “The trick with metamaterials is that the surface layer looks to the radiation as it has an effective plasma frequency of 1THz just controlled by geometry.

Without the pits, 1THz radiation is loosely confined to the first 20mm above the metal. With appropriate pits this drops to a fraction of 1mm. “It would be nice to increase this further by 10 times,” said Maier. “To do this we will have to fill the holes with a high refractive index material such as silicon.”

Now the technique has been proven by experiment, the universities intend to manipulate the radiation by varying the pit size across the surface. Waveguides are one target and “we should be able to construct a two-dimensional lens that will concentrate THZ radiation passing across a sheet around one point on that sheet”, said Maier.

THz spectrometry is a technique made possible by the recent invention of practical compact THz sources and detectors. Such a lens could increase the sensitivity of THz spectrometry on molecules dropped onto the surface.

For this kind of analysis, the surface will also need more bandwidth. “Our metamaterial gives good confinement over a very narrow frequency band,” said Maier. “We need a couple of THz and are looking at ways, but I can’t comment on them at the moment.”

Source: Electronics Weekly.

Successful application development of this in-process cure monitoring technique will substantially reduce costs relative to the current methods utilized, which are contact in nature. As a result, the current method can only identify a bad coating after completion which would then require substantial scrap and rework in order to produce good parts. Since the terahertz (THz) method would monitor the process in real time, allowing for process adjustments, it has the potential to materially reduce scrap and rework and thus improve productivity in the production of the next generation of fighter jets. Picometrix has partnered with Northrup Grumman in order to accelerate their adoption of this technique once developed. Northrup Grumman has the prime contract to produce up to $100 trillion of the next generation fighter jets for the Air Force through 2050.

Upon a successful completion of Phase II, the THz specialty coating monitoring inspection system will provide the Air Force a highly capable, in-process, non-contact and accurate method for measuring the thickness and cure state of coatings such as polyurethanes used in aircraft. The proposed system will not only be able to monitor the specialty coatings of interest to the Air Force, but also other coatings of interest to the Army and Navy. In addition, the method could be applicable for monitoring and inspecting coatings and paints applied in industrial settings, such as automobile manufacturing.

Once completed, the system will consist of the T-Ray™ 4000 control unit which is connected to a miniature terahertz transceiver via a flexible umbilical up to 100 meters in length mounted onto an existing robot arm within a paint booth. The fiber-optic coupled THz technology employed is well suited to the application, as the sensors are small, light weight and freely positionable. A hand-held version that would allow measurement on cured coatings without the robot is also planned.

“This specialty coating application is another example of the extensive list of NDT markets for our terahertz technology. Our T-Ray™ 4000 system platform is ideally suited for on-line, real time applications that address difficult and high value-added NDT challenges,” commented Richard (Rick) Kurtz, CEO of API.

The research shows that these T-rays, electromagnetic waves in the far infrared part of the electromagnetic spectrum that have a wavelength 500 times longer than visible light, can be guided along the surface of a specially designed material, known as a metamaterial. Being able to control T-rays in this way is essential if this type of radiation is to be used in many real world applications.

Researchers believe one of the areas with the most potential to use T-rays is security sensing and scanning, because many of the molecules in explosives and biological agents like anthrax strongly absorb this radiation. If T-rays are tightly confined on surfaces in contact with such molecules then the detection sensitivity is greatly increased.

Simple metallic surfaces have been used to control T-ray propagation before, but these only weakly guide the radiation, which extends as a weak field many centimetres above the surface of the material, thus rendering it less effective for sensing. The new study has now shown that a metamaterial surface draws T-rays close to it, creating a very strong field less than a millimetre above the surface. This greatly enhances the absorption by molecules on the surface making highly effective sensing techniques possible.

The study was performed by a team of UK and Spanish physicists led in the UK by Dr Stefan Maier from Imperial College London’s Department of Physics, and Dr Steve Andrews of the University of Bath. Dr Maier explains why their metamaterial design is so important:

“T-rays have the potential to revolutionise security screening for dangerous materials such as explosives. Until now it hasn’t been possible to exert the necessary control and guidance over pulses of this kind of radiation for it to have been usable in real world applications. We have shown with our material that it is possible to tightly guide T-rays along a metal sheet, possibly even around corners, increasing their suitability for a wide range of situations.”

A metamaterial is a man-made material with designed electromagnetic properties which are impossible for natural materials to possess. The metamaterial created for this new research consists of a metallic surface textured with a two-dimensional array of pits. The researchers chose the dimensions of the pits so that T-rays are drawn closely to them as they travel along the surface.

Dr Andrews says that although the results of their study are very promising, more work is needed to refine the technology before such surfaces can be used for sensing applications. “At the moment only a small number of the frequencies that make up a pulse of T-ray radiation are closely confined by our metamaterial. More sophisticated designs are needed in order to make sure that the whole pulse is affected by the surface structure, so that absorption features of molecules can be clearly identified.”

Dr Maier and Dr Andrews designed the metamaterial together with colleagues from Universities in Madrid and Zaragoza, with financial support from the US Air Force and the Royal Society. Their breakthrough is based on previous theoretical predictions obtained by the Spanish team together with Imperial’s Professor John Pendry, published in Science in 2004.

Authors: C. R. Williams, S. R. Andrews, S. A. Maier, A. I. Fernandez-Dominguez, L. Martin-Moreno, and F. J. Garcia-Vidal.

Journal article: ‘Highly confined guiding of terahertz surface plasmon-polaritons on structured metal surfaces’ Nature Photonics, Sunday 3 January 2008.

Source: Science Daily.

The Leeds team has secured a new grant of £2 million from the Engineering and Physical Sciences Research Council (EPSRC) to shed light on the changes in behaviour and properties of nano-scale systems within the least explored area of the electromagnetic spectrum, the terahertz region.

The combined expertise at Leeds will fuse two fundamental areas of science – nanoscience, which focuses on decreasing size, and high frequency science, which focuses on high speed electronics.

Project leader Dr John Cunningham of the School of Electronic and Electrical Engineering explains: “The dimensions of electronic devices have reduced so much that they can be literally a few atoms in size – but at this scale, they exhibit different properties than their larger scale counterparts. These properties can be directly revealed or even changed using radiation from the terahertz region of the spectrum. If we want to continue to provide ever-smaller electronic systems that work at ever-faster speeds, we must find new ways of enabling this development by understanding exactly how they work. It’s an exciting project for us because we’re bringing together two areas of fundamental science that have rarely been studied together.”

Technologies using the radiation from many regions of the electromagnetic spectrum are well developed: the use of radio waves, x-rays and microwaves are now second nature in modern life. But the terahertz region, often called the ‘Terahertz gap’ because of the lack of commercially available sources and detectors for this region, is considered to be the ‘final frontier’ in understanding the electromagnetic spectrum. The Leeds team believes that its unique properties could offer the gateway to the next generation of new nano-electronics.

Terahertz radiation is found in the electromagnetic spectrum between the microwave region (where satellite dishes and mobile phones work) and infra-red light, but ways to generate detect and analyse terahertz radiation are not as advanced as other imaging techniques.

The four-year project will develop new methods to examine and assess nanoscale electronic systems using terahertz radiation, Future applications may include the development of new nano-scale high-frequency electronic devices in areas such as sensing, imaging and spectroscopy, and ultimately in communications.

Source: University of Leeds

In terms of technological innovation, Mantis is the first ultrafast laser system to incorporate a 5 watt green pump laser based on monolithic OPSL (optically pumped semiconductor laser) technology rather than a traditional DPSS pump.

(OPSL technology has been widely used in demanding OEM applications such as bio-instrumentation for several years).

A major application for the Mantis is seeding short pulse amplifier/OPA systems to generate tunable high energy, sub-35 fs pulses for a wide range of pulse-probe experiments in physics and chemistry.

Typical examples include studies into molecular photodissociation dynamics and power hungry techniques such as fluorescence upconversion.

Another application area is THz spectroscopy and imaging.

Here the simple to use Mantis oscillator will generate a wider spectrum of THz radiation, because of the laser’s very short pulsewidth.

Source: Laboratory Talk

T-rays, pulses of terahertz radiation, could also illuminate penciled sketches under paintings on canvas without harming the artwork, the researchers say. Current methods of imaging underdrawings can’t detect certain art materials such as graphite or sanguine, a red chalk that some of the masters are believed to have used.

The team of researchers, which includes scientists at the Louvre Museum, Picometrix, LLC and U-M, used terahertz imaging to detect colored paints and a graphite drawing of a butterfly through 4 mm of plaster. They believe their technique is capable of seeing even deeper. A paper on the research is published in the February edition of Optics Communications.

In March, the scientists will take their equipment to France to help archaeologists examine a mural they discovered recently behind five layers of plaster in a 12th century church.

“It’s ideal that the method of evaluation for historical artifacts such as frescoes and mural paintings, which are typically an inherent part of a building’s infrastructure, be non-destructive, non-invasive, precise and applicable on site. Current technologies may satisfy one or more of these requirements, but we believe our new technique can satisfy all of them,” said John Whitaker, an author of the paper who is a research scientist and adjunct professor in the Department of Electrical Engineering and Computer Science at U-M.

Terahertz imaging can reveal depth and detail that other techniques cannot, Whitaker said. And it’s not potentially harmful like X-ray imaging because terahertz radiation is non-ionizing. Its rays don’t have enough energy to knock electrons off atoms, forming charged particles and causing damage, like X-rays do.

While terahertz radiation is all around us in nature, it has been difficult to produce in a lab because it falls between the capabilities of electronic devices and lasers.

“Terahertz is a strange range in the electromagnetic spectrum because it’s quasi-optical. It is light, but it isn’t,” said Bianca Jackson, first author of the paper who is a doctoral student in applied physics.

The device used for this research is a hybrid between electronics and lasers. It was developed by the Ann-Arbor based company Picometrix. It’s called the T-Ray™ system, and it uses pulses from an ultra-fast laser to excite a semiconductor antenna, which in turn emits pulses of terahertz radiation.

The rays permeate the plaster, and some reflect back when there is a change in the material. When they bounce back and how much energy they retain depends on the material they hit. Different colors of paint, or the presence of graphite, for example, cause tell-tale differences in the amount of energy in the returning waves. A receiver measures this energy, and the scientists can use the data to produce an image of what lies beneath, Jackson explained.

A similar device made by Picometrix is used routinely to examine the foam on the space shuttle’s fuel tanks for underlying damage, said Irl Duling, director of terahertz business development at Picometrix and an author of the paper. This paper discusses a new application, rather than a new device.

Gèrard Mourou, a U-M electrical engineering professor emeritus, said he believes this technique will be especially useful in Europe, where historic regime changes often resulted in artworks being plastered or painted over. This was common in places of worship, some of which switched from churches to mosques and vice versa over the centuries.

“In France alone, you have 100,000 churches,” Mourou said. “In many of these places, we know there is something hidden. It has already been written about. This is a quick way to find it.”

And Leonardo DaVinci’s “The Battle of Anghiari,” for example, is believed to lurk beneath other frescos at the Palazzo Vecchio in Florence, Italy, Mourou said.

The paper is called “Terahertz imaging for non-destructive evaluation of mural paintings.”

Source: University of Michigan

Teraview, which is headquartered in Cambridge, UK, and was a spin off from the Toshiba Cambridge Research Laboratory in April 2001, developed its online system based on its terahertz technology to carry out high speed measurements of the thickness of the coating of tablets, and recently won an important endorsement from the US Food and Drug Administration.

Pharmaceutical companies are forever striving to increase their quality. In the production of tablets quality checks are carried out routinely during the process and batches are closely inspected and sampled against any problems. This can be quite an intensive process but it is still absolutely essential to maintain the expected quality standards.

Teraview’s system can also be used to measure other characteristics of the tablet such as core density, or delamination (other studies published in conjunction with the FDA have suggested that terahertz systems could replace wet dissolution testing).

Now, Teraview in conjunction with its partners have carried out “successful proof of principle for high speed measurements of coating thickness on tablets applicable to on-line tablet inspection”.

Dr Don Arnone, chief executive of TeraView, commented: “This study is exciting news for our pharmaceutical customers. It enables us to provide Terahertz solutions to address their business issues from early stage product development all the way through to assuring product performance during manufacture. It is also good news for the company because it has the potential to expand our footprint in the pharmaceutical manufacturing market in the future.”

So how does it work?

The terahertz system works by using a series of spectroscopic sensors operating in the terahertz spectrum of electromagnetic radiation that is between visible light and radio waves. The sensors have proven that they can be used to measure both quickly and accurately the coating thickness of tablets that are in rapid motion in a coating vessel.

This leads to the next stage where the terahertz sensors could be used to control the tablet coating/production process using simple feedback systems. Clearly it would be useful to have accurate and rapid sensors to control continuous processing systems.

The pharmaceutical industry is becoming interested in continuous processing as has been seen recently with the Massachusetts Institute of Technology (MIT)/Novartis link up worth $65 million to MIT to develop a continuous manufacturing pharmaceutical facility (announced in September 2007).

Teraview has already shown in numerous studies with the FDA and several large pharmaceutical companies that the terahertz system can provide structural and chemical information on the tablet and capsule contents that cannot be attained by commonly used techniques. The technology appears now to be maturing to a state where it can be widely adopted.

Source: LabTechnologist.com

More about TeraView.

It also means microchips that communicate wirelessly, and – a bit down the road – medical imaging technology much more precise and cheaper, at the terahertz level.

That’s terahertz.

Imagine you want to wirelessly transfer a high definition movie from your Apple TV to you mobile device. Sounds like it might take forever, but according to Adam Renstchler, director of business development for Phiar, it wouldn’t if using gadgets equipped with this new radio technology.

“If I have a radio that’s fast enough to that,” he said, “then my calendar and my contacts will be super fast.”

The signal would travel on the 60 GHz unlicensed spectrum, a frequency previously unusable without the technology to access it. Unlike the 700 MHz spectrum major players like Google, Verizon, and AT&T are vying for because of its ability to penetrate walls, mountains, trees – whatever – this spectrum won’t even penetrate the next room. The idea then, is that whatever wireless activity you’re doing in one room won’t interfere the signal in another room.

It could also make a digital-theft-wary Hollywood very happy as well, as tt also means your wireless Internet setup won’t bleed out into your neighbor’s house. Then again, if you wanted it to bleed into the next room, it wouldn’t.

Nonetheless, Renstchler says Phiar has entered a joint development agreement with Motorola, and with a European company yet to be announced. Similar technology, galleon-arsenide diodes, was previously only deployed on satellites. Renstchler says Phiar’s diode beat it in millimeter wave detection, making it a class above satellite technology for five times cheaper.

This is where it starts to get complicated, so if you’d like to bail, I won’t be offended.

Renstchler hearkens back to the first introduction of semiconductors, when vacuum tubes were still superior. Over a short period time, obviously, that changed. He says we’re at the same point in history with amorphous thin film technology that works via the principle of quantum tunneling, as only diodes are possible now, and transistors are years down the road. Instead of hazarding a less-than-stellar explanation, check out Phiar’s website for visual and textual explanations of quantum tunneling.

This method allows for radio reception as lightweight and low power as an old-fashioned crystal radio, yet it much more information can be sent and received. Because the technology is thin and amorphous, it allows analog electronics to be built on silicon-based digital CMOS chips. Think of it as a very small antenna placed right on the microchip. But the technology takes it beyond the physical limits of semiconductors.

Renstchler says you could throw these chips into a bag, and they would be able to communicate and wirelessly configure themselves.

Many of the applications, including the development of these chips are still years from completion, and the Federal Communications Commission doesn’t even have existing regulation for the frequencies they operate on. “The inherent physics of our devices will allows us to build radios that will have carrier frequencies at 1-2 terahertz.”

The FCC regulates up to 275 GHz. “So we’re in the Wild West in sub-millimeter frequencies.”

Phiar will be selling its first commercial product in 2009.

Source: WebProNews.

The work has implications for the future development of ultra-high frequency transistors and wiring in electronic circuits - and academics say their findings have singled graphene out as the “best possible” material for electronic applications.

With a high electronic quality - measured at around 200,000 cm2/Vs and more than 100 times higher than for silicon - researchers believe graphene has the potential to improve upon the capabilities of current semiconductors and open up exciting new possibilities. These include ultra-high frequency detectors required for full-body security scanners, which would make people transparent by operating at terahertz (THz) frequencies.

The research is reported in the latest issue of the American Physical Society’s journal Physical Review Letters, and has been carried out in conjunction with The Institute for Microelectronics Technology in Russia, The University of Nijmegen in the Netherlands and The Department of Physics at Michigan Technological University in the United States.

“The search is on for materials with higher electronic quality or intrinsic mobility, which should improve the existing applications and open up new ones,” said Professor Andre Geim, one of the paper’s authors and director of The University of Manchester’s Centre for Mesoscience and Nanotechnology.

“Graphene exhibits the highest electronic quality among all known materials - higher than copper, gold, silicon, gallium arsenide, carbon nanotubes, and anything we know. It is the only material where electrons at room temperature can move thousands of interatomic distances without scattering.

“We knew that it could be a long distances and longer than for silicon, but before our latest work we did not know, nor expected, that graphene could beat carbon nanotubes or the record holder Indium antimonide (InSb). Our work singles it out as the best possible material for electronic applications.

“Our findings mean it is worth investing even more effort to develop the material into viable products.

“Neither graphene nor carbon nanotubes can hope to compete with silicon for about another 20 years. The advantage of graphene is that it still holds a lot of promise, which must be investigated.

“The major problems for nanotubes do not exist for graphene. It does have its own problems but they seem doable at least, unlike those for nanotubes, which seemed impossible a few years ago and remain impossible now.

“Whatever comes out as applications, the physics is extremely rich and one can be sure that graphene is here to stay as long as silicon or gallium arsenide, with many more interesting effects to be found. Higher mobility will be a powerful facilitator.”

Geim believes graphene-based devices like chemical gas sensors and THz sources and detectors could begin to materialise within three to five years.

Prof Geim added: “Our work puts fundamental limits on what can be potentially done by using graphene. Previously, researchers speculated that the sky was the limit for graphene’s electronic quality. Now we know this limit accurately enough. It is not endless but sky-high.”

A recent invention to come out of CREOL is a pair of special goggles that let people see through clothing, plastic, ceramics, wood and paper, said Matthew Weed, a graduate research assistant at CREOL. The heat-sensitive goggles can also detect human bodies and animals through walls and at night.

“What we do is make the things that they can do on TV easier or better,” Weed said.

The goggles use infrared frequency waves to detect motion of anything giving off heat. Images appear green through the goggles.

Weed said that defense research groups in CREOL are working on improving this technology, which has already been used by the military and government.

Researchers are also working with another type of frequency known as terahertz, or T-rays.

Because of their short wavelengths, T-rays, frequency units equal to one trillion hertz, can pass through most materials except metal and water.

Amitabh Ghoshal, a graduate research assistant at CREOL, said that the use of T-ray imaging may soon be used to detect weapons hidden underneath clothing.

He noted that ceramic guns have recently become available that are undetectable by standard metal detectors.

But because the ceramic guns are so dense, T-ray imaging devices can still detect them. The T-ray waves could detect any solid object under a person’s clothing and then produce the image back on a screen.

Weed added that researchers are working to develop large T-ray screens to view crowds of people and allow for more effective security in airports.

Ghoshal said that there would have to be some debate to determine if this kind of technology is an invasion of privacy.

“As far as I can tell, the privacy laws were written with ideas about privacy before this kind of technology was possible,” Ghoshal said. “It will probably take some debate exactly where this [kind of imaging technology] falls in the spectrum of private to public.”

Weed added that the low resolution of the T-ray images won’t expose too much of a person’s body.

“It’s not that we just see through their clothes and can see everything else,” Weed said. “It’s more like we see ghostly images of them that would show, brightly, something solid like a gun or a knife or a phone or a camera for that matter.”

T-rays can also be used to see through skin to detect abnormalities in the body.

According to the Rensselaer Polytechnic Institute’s Center for Terahertz Research Web site, T-rays offer advantages that conventional imaging technology, such as X-rays, does not. T-rays’ low energy levels allow for the imaging of human tissue without harmful radiation, making them safer than X-rays.

“If you look around you, optics permeates so many technologies,” said Jannick Rolland, associate professor of optics at CREOL.

Researchers at CREOL are working to create T-ray, laser-based imaging tools. Rolland said these devices will allow doctors to probe a skin lesion in a fraction of a second. The image will show any signs of early or advanced stages of cancer in the body, without having to actually cut a portion of skin off.

“Medicine of the future will move away from animal models and be able to operate on engineered tissue that can be probed with light, non-destructively, to study new drugs or vaccines,” Rolland said.

Source: Orlando Sentinel

The group, led by UCSB physicist Mark Sherwin, combined the talents of the UCSB scientists—physicists S. James Allen and Elliot Brown, molecular biologist Kevin W. Plaxco, biochemist Song-I Ha, experimental cosmologist Phil Lubin, and electrical engineer Mark Rodwell—and Louis Claude Brunel and Johan van Tol—scientists with the National Magnetic Field Laboratory at FSU—to better understand how proteins work in life processes.

“In orde