Technique Boosts THz Production

A new technique for producing more efficient terahertz radiation could lead the way to more powerful sensing and imaging technologies that can see through opaque materials.

The terahertz band of the electromagnetic spectrum has a lot of unlocked potential. The radiation band is low energy, allowing it to penetrate otherwise opaque materials, but the frequency of the band is higher than that achievable by current electronic circuits, and the frequency is too low to be picked up by optical instruments.

Terahertz generation. A strong THz emission from the center of the device is observed in the tip-to-tip design (top). The electrodes are the black lines in the center of the device. The colors show the electric field from low (blue) to high (red) values. Much weaker electric fields and THz emission are seen in the interdigitated electrode design (bottom).(Image: From Ref. 1 © 2012 H. Tanoto)

Researchers at the Agency for Science Technology and Research's (A*STAR) Institute of Materials Research and Engineering generated THz radiation 100 times stronger than that created by conventional means. Normally, to create THz radiation, two optical lasers of similar frequencies are shone on a semiconductor, causing it to emit light with the difference of the lasers' frequencies. For sufficiently small differences, the radiation will be in the THz band.

Metal electrodes are used to serve as antennae and amplify this weak effect. The electrodes that are used to link semiconductors in series are normally arranged in an interlacing pattern. The researchers discovered that if they changed the orientation of the leads to be tip-to-tip, the gap between the contacts narrowed, and the resultant electric field aligned with the THz lightwaves. This provided a much stronger antenna enhancement.

The researchers believe that this arrangement can be miniaturized for implementation in compact THz sources.

“This approach will greatly facilitate the applications of THz technology in areas such as gas sensing, nondestructive inspection and testing, high-resolution spectroscopy, product quality monitoring and bioimaging,” said research leader Jinghua Teng.

For more information, visit: www.a-star.edu.sg