January 22, 2012
We recently looked at one of the potential contenders in the US$10 million Qualcomm Tricorder X PRIZE, which as the name suggests, was inspired by the medical tricorder of Star Trek fame. Now scientists have developed a new way of creating Terahertz (THz) or T-rays, which they say could help make handheld devices with tricorder-like capabilities a reality.
T-rays are electromagnetic waves in the far infrared part of the spectrum that have a wavelength hundreds of times longer than visible light. With their ability to penetrate fabrics and plastics, T-rays are already used in full-body security scanners at many airports to detect weapons, drugs and explosives. But with T-rays being non-ionizing - unlike X-rays - and every molecule having its own signature in the THz range, it is their potential for medical and other applications that have the researchers excited.
Not only can THz waves detect biological phenomena, such as increased blood flow around tumorous growths, but they can also sense molecules such as those present in cancerous tumors and living DNA. Additionally, T-rays can also be used in gas pollution monitoring and non-destructive testing of semiconductor integrated circuit chips.
While we've seen compact T-ray spectrometers before, researchers from the Institute of Materials Research and Engineering (IMRE) at the Agency for Science, Technology and Research (A*STAR) in Singapore and Imperial College London in the UK say they have developed a way to produce stronger and more efficient T-rays at room temperature conditions in a much stronger directional beam than was previously thought possible. It is this breakthrough they claim will allow future T-ray systems to be smaller, more portable, easier to operate, and much cheaper.
The team produced a strong beam of T-rays by shining light of differing wavelengths on a pair of electrodes, which took the form of two pointed strips of metal separated by a 100 nanometer gap placed on top of a semiconductor wafer. This tip-to-tip nano-sized gap electrode structure acts like a nano-antenna to significantly enhance the THz field and amplify the THz wave generated. The researchers say that arrays of their new nano-antennas can generate a power output that is 100 times higher than the output of commonly used THz sources, which provides T-ray imaging devices with more power and higher resolution. As the wavelength of the T-rays can be tuned, the researchers are able to create a beam that is useable in the scanning technology.
"T-rays promise to revolutionize medical scanning to make it faster and more convenient, potentially relieving patients from the inconvenience of complicated diagnostic procedures and the stress of waiting for accurate results," said study co-author, Stefan Maier. "Thanks to modern nanotechnology and nanofabrication, we have made a real breakthrough in the generation of T-rays that takes us a step closer to these new scanning devices. With the introduction of a gap of only 0.1 micrometers into the electrodes, we have been able to make amplified waves at the key wavelength of 1000 micrometers that can be used in such real world applications."
The team's paper, "Greatly enhanced continuous-wave terahertz emission by nano-electrodes in a photoconductive photomixer," is published in the journal Nature Photonics.