Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Lehigh researchers hone radiation source for THz devices

23.02.2004


Potential applications in medicine, remote sensing, imaging and satellite communications



A world that consumes information in gigabytes may one day find terahertz-sized solutions for some of its most pressing problems.

While one gigabyte is equal to one billion (109) bytes of information, a terahertz (THz) is a unit of electromagnetic-wave frequency equivalent to one trillion (1012) hertz, with one hertz equaling one cycle per second.


Terahertz (THz) frequencies, ranging from 0.1 to 10 THz, have potential applications in medicine, remote sensing, imaging and satellite communications, but are nonetheless one of the most under-utilized frequency ranges. That is because the THz range lies between the microwave frequency range and the near-infrared and optical frequency ranges, in which conventional semiconductor devices are usually operated.

Yujie J. Ding, professor of electrical and computer engineering and a member of Lehigh University’s Center for Optical Technologies, is working to solve challenges that must be overcome for THz devices to become readily accessible and cost-effective.

"We need a source to generate coherent THz waves and we need detectors," says Ding, a specialist in optoelectronics, nonlinear optics and quantum electronics.

"This is very challenging because the concepts that govern infrared light and visible light don’t work with THz."

Ding hopes to develop a compact THz radiation source with wide tunability in the wavelength range of 30 to 3,000 microns (a micron is equal one one-millionth of a meter). Several methods have been advanced by other researchers, but most have shortcomings. Free-electron lasers are bulky and costly. Ultrafast lasers generate very weak THz beams with low output powers and pulse energies.

Ding and his research group, which includes four Ph.D. candidates, one M.S. candidate and two post-doctoral researchers, have developed a method of focusing two high-frequency lasers to generate tunable and coherent THz waves in the range of 58 to 3540 microns.

In the Aug. 4 issue of Applied Physics Letters, Ding described his work in an article titled "Continuously tunable and coherent terahertz radiation by means of phase-matched difference-frequency generation (DFG) in zinc germanium phosphide ZnGeP2."

In the article, Ding reported a highest-output peak power seven orders of magnitude higher than any output power previously reported for a THz source. He also reported a tuning range of output wavelengths that was about five times wider than a range reported previously by researchers generating THz waves in ZnGeP2 using two carbon-dioxide laser lines.

Last year, Ding reported successful THz radiation using gallium-selenide crystals in an article titled "Efficient, tunable and coherent 0.18-5.27-THz source based on GaSe crystal," which was published Aug. 15, 2002, in the journal Optics Letters.

A properly tuned source emitting THz frequencies, says Ding, would be ideally suited for imaging, spectroscopy and medical diagnostics, including cancer detection and, potentially, gene therapy.

Because vibrations of DNA and RNA chains resonate in THz, Ding says, "with a proper THz radiation source, you can tune across the resonances and sense very slight changes of the atomic chain arrangement."

Cancer cells, especially melanoma tissues, also vibrate in THz, says Ding, and lend themselves to early detection by doctors equipped with THz devices.

THz devices are also promising for homeland security tasks such as detecting the presence of toxic and semitoxic gases, says Ding. When subjected to THz waves, he says, gaseous materials reveal a limited number of sharp peaks that form a distinct pattern like a fingerprint. When the same material is subjected to the much shorter visible or mid-infrared light waves, the peaks that are revealed are too congested to show an observable pattern. Ding has already performed experiments on water vapor using THz waves at Lehigh.

Ding’s next challenge is to scale down his THz radiation device, which now approaches a large shoe box in size. His ultimate goal is to fit 10 arrays, each equipped with an emitter, a detector and photonic bandgap crystals, and each measuring millimeters in size, onto one computer chip wafer of standard dimensions.

To miniaturize his THz device, Ding is using nanostructure quantum dots and including photonic bandgap crystals that act as a special waveguide by tightly focusing the THz beam on a particular detector. The result is a more sensitive detecting tool that detects the presence of a specific toxic chemical when that chemical blocks part of the THz beam. "Without the photonic bandgap crystals, the beam will diverge," says Ding.

Kurt Pfitzer | EurekAlert!
Further information:
http://www.lehigh.edu/

More articles from Physics and Astronomy:

nachricht New survey hints at exotic origin for the Cold Spot
26.04.2017 | Royal Astronomical Society

nachricht NASA's Fermi catches gamma-ray flashes from tropical storms
25.04.2017 | NASA/Goddard Space Flight Center

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Making lightweight construction suitable for series production

More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.

Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...

Im Focus: Wonder material? Novel nanotube structure strengthens thin films for flexible electronics

Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.

"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

7th International Conference on Crystalline Silicon Photovoltaics in Freiburg on April 3-5, 2017

03.04.2017 | Event News

 
Latest News

Link Discovered between Immune System, Brain Structure and Memory

26.04.2017 | Life Sciences

New survey hints at exotic origin for the Cold Spot

26.04.2017 | Physics and Astronomy

NASA examines newly formed Tropical Depression 3W in 3-D

26.04.2017 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>