Tiny transmitter sets frequency record: Revolutionary terahertz transmitter developed

ScienceDaily (Jan. 13, 2012) — A terahertz transmitter developed at the TU Darmstadt has generated the highest frequency ever attained by a microelectronic device. The innovative device is also minuscule and operates at room temperature, which could lead to it paving the way for new applications in, e.g., nondestructive testing or medical diagnostics.

Although terahertz (THz) electromagnetic radiation, which has wavelengths ranging from 0.1 mm and 1 mm, penetrates common materials, such as plastics, paper, fabrics, or ceramics, allows, e.g., nondestructively testing workpieces, analyzing processes occurring in engine combustion chambers while engines are running, inspecting packages and letters for hazardous biological substances without need for opening them, it has yet to establish a reputation for itself in scientific and engineering fields. One of the hindrances involved was that, until now, transmitters and receivers operating at THz?frequencies were bulky and very expensive.

However, that situation might soon be reversed, since a team of physicists and engineers led by Dr. Michael Feiginov at the TU?Darmstadt's Institute for Microwave Technology and Photonics has developed a resonance tunnel diode (RTD) for generating terahertz electromag­netic radiation that takes up less than a square millimeter and may be produced using more or less conventional semiconductor-device fabrication technologies. Furthermore, their innovative transmitter has set a new frequency record, 1.111 THz, for microelectronic devices.

The highest frequency ever generated by an active semiconductor device

Feiginov, a physicist, noted, that, "That is the highest frequency ever generated by an active semiconductor device." He was also able to theoretically prove that a minuscule transmitter, like that developed by his group, should be capable of generating much higher frequencies extending up to 3 THz. As Feiginov, who intends to continue pursuing development work on the transmitter over the coming years until generation of such higher frequencies has been achieved, went on to say, "That was formerly regarded as impossible by those involved in terahertz research." Achieving such higher frequencies would allow attaining better spatial resolutions, i.e., recognizing finer details, employing terahertz electromagnetic radiation in materials testing and analysis than would be possible at lower frequencies.

That the RTD his group has developed operates at room temperature makes it even more attractive for use in engineering applications. He further commented that, "It might, for example, be utilized in spectroscopic analyses of molecules that have transitions falling within the THz?range." According to Feiginov, that would mean that substances that have thus far escaped spectroscopic analysis in the THz?range could be investigated employing that widely practiced, scientific method, which would be of great benefit in various fields, among them medicine, where it might, e.g., allow distinguishing diseased body tissues from healthy body tissues in vivo. Since active semiconductor devices, such as the THz?transmitter developed by the TU?Darmstadt group, represent the heart of modern informatics and telecommunications technologies, as well as all sorts of electronic equipment, Feiginov presumes that the device developed by his group will prove useful in many other application areas that cannot readily be foreseen at this stage. As he put it, "Extracting higher frequencies from the device would lead to new applications, or application areas, in the fields of computers, mobile telephones, and other types of electronic equipment."

In the course of miniaturizing their new device, the group of TU?Darmstadt researchers spent the past few years taking microelectronics close to the limits of the technically feasible. The heart of their RTD is a dual-barrier structure, within which a quantum well (QW) is embedded. A QW is a very thin layer of indium-gallium arsenide semiconductor sandwiched between a pair of ultrathin barrier layers of aluminum-arsenide semiconductor. Every one of those layers is just one nanometer to a few nanometers thin. This dual-barrier structure, plus a quantum-mechanical effect, provides that electromagnetic waves generated within a terahertz oscillator will be repeatedly amplified, rather than attenuated, which means that the oscillator will emit continuous-wave electromagnetic radiation at terahertz frequencies. The group of TU?Darmstadt researchers collaborated with ACST GmbH, a local fabricator of microelectronic circuit components, in producing their diode.

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The above story is reprinted from materials provided by Technische Universit?t Darmstadt, via AlphaGalileo.

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Journal Reference:

Michael Feiginov, Cezary Sydlo, Oleg Cojocari, Peter Meissner. Resonant-tunnelling-diode oscillators operating at frequencies above 1.1?THz. Applied Physics Letters, 2011; 99 (23): 233506 DOI: 10.1063/1.3667191

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New revolutionary material can be worked like glass

ScienceDaily (Nov. 18, 2011) — A common feature of sailboards, aircraft and electronic circuits is that they all contain resins used for their lightness, strength and resistance. However, once cured, these resins can no longer be reshaped. Only certain inorganic compounds, including glass, offered this possibility until now. Combining such properties in a single material seemed impossible until a team led by Ludwik Leibler, CNRS researcher at the Laboratoire "Matière Molle et Chimie" (CNRS/ESPCI ParisTech), developed a new class of compounds capable of this remarkable feat. Repairable and recyclable, this novel material can be shaped at will and in a reversible manner at high temperature.

And, quite surprisingly, it also retains certain properties specific to organic resins and rubbers: it is light, insoluble and difficult to break. Inexpensive and easy to produce, this material could be used in numerous industrial applications, particularly in the automobile, aeronautics, building, electronics and leisure sectors. This work is published on 18 November 2011 in Science.

Replacing metals by lighter but just as efficient materials is a necessity for numerous industries, such as aeronautics, car manufacturing, building, electronics and sports industry. Due to their exceptional mechanical strength and thermal and chemical resistance, composite materials based on thermosetting resins are currently the most suitable. However, such resins must be cured in situ, using from the outset the definitive shape of the part to be produced. In fact, once these resins have hardened, welding and repair become impossible. In addition, even when hot, it is impossible to reshape parts in the manner of a blacksmith or glassmaker.

This is because glass (inorganic silica) is a unique material: once heated, it changes from a solid to a liquid state in a very progressive manner (glass transition), which means it can be shaped as required without using molds. Conceiving highly resistant materials that can be repaired and are infinitely malleable, like glass, is a real challenge both in economic and ecological terms. It requires a material that is capable of flowing when hot, while being insoluble and neither as brittle nor as "heavy" as glass.

From ingredients that are currently available and used in industry (epoxy resins, hardeners, catalysts, etc.), researchers from the Laboratoire "Matière Molle et Chimie" (CNRS/ESPCI ParisTech) developed a novel organic material made of a molecular network with original properties: under the action of heat, this network is capable of reorganizing itself without altering the number of cross-links between its atoms. This novel material goes from the liquid to the solid state or vice versa, just like glass. Until now, only silica and some inorganic compounds were known to show this type of behavior. The material thus acts like purely organic silica. It is insoluble even when heated above its glass transition temperature.

Remarkably, at room temperature, it resembles either hard or soft elastic solids, depending on the chosen composition. In both cases, it has the same characteristics as thermosetting resins and rubbers currently used in industry, namely lightness, resistance and insolubility. Most importantly, it has a significant advantage over the latter as it is reshapeable at will and can be repaired and recycled under the action of heat. This property means it can undergo transformations using methods that cannot be envisaged either for thermosetting resins or for conventional plastic materials. In particular, it makes it possible to produce shapes that are difficult or even impossible to obtain by molding or for which making a mold is too expensive for the envisaged purpose.

Used as the basis of composites, this new material could therefore favorably compete with metals and find extensive applications in sectors as diverse as electronics, car manufacturing, construction, aeronautics or printing. In addition to these applications, these results shed unexpected light on a fundamental problem: the physics of glass transition.

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The above story is reprinted from materials provided by CNRS (Délégation Paris Michel-Ange).

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Journal Reference:

D. Montarnal, M. Capelot, F. Tournilhac, L. Leibler. Silica-Like Malleable Materials from Permanent Organic Networks. Science, 2011; 334 (6058): 965 DOI: 10.1126/science.1212648

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The revolutionary wave disc generator combustion engine

 The mid-term future for fuel efficient vehicles with useful range is likely a hybrid solution of electric motors powered by batteries, topped up by a fuel-burning generator. Dr. Norbert Müller at Michigan State, backed by $2.5 million from the US Government, aims to make that last part of the equation a much more compact and efficient proposition with a revolutionary new form of combustion engine.

The culmination of years of research, the latest version is in the form of a spinning metal disc with precisely-calculated radial channels. Fuel/air mixture enters via the central hub and travels outwards. As the disc spins the channel exit becomes closed off causing a back-shock. Because the inlet port is now closed off to the channel this causes compression (like a piston) and the fuel/air mixture is then ignited. The expansion of the explosion powers the wheel, opening the channel once more to the inlet and outlet ports. The exhaust gas is ejected and fuel/air is sucked in to repeat the process - at very high speed naturally.

This elegant design does away with many of the moving parts and circulatory systems of conventional combustion engines that lower their fuel-use efficiency, typically 15%. Dr. Müller is obtaining efficiencies of 60% with the wave disc design and of course the weight of the engine is greatly reduced.

"Our goal is to enable hyper-efficient hybrid vehicles to meet consumer needs for a 500mile driving range, lower vehicle prices, full-size utility, improved highway performance and very low operating costs," says Müller. "The WDG (Wave Disc Generator) also can reduce carbon dioxide emissions by as much as 95% in comparison to modern internal combustion engine vehicles."

While the team's focus is very much on automotive use, for obvious reasons, there is clearly potential for the creation of very compact and efficient electricity generators that would sell in vast numbers across the world. For the moment however this all still in the research phase and we have to take the team's claims of potential emissions reduction on trust.

A "car-sized" 25 kW (33.5 hp) version of the working prototype is due by the end of the year with further funding required after February 2012. We hope Dr. Müller and his team get the money they need to bring this elegant solution to a pressing need to market as soon as possible.

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