Laser-powered terahertz system to see deeper into patients

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A laser-powered terahertz source and detector system that sees deeper into tissues without the damaging effects of X-rays has been created.

An electrical engineering research team at the University of Michigan developed the system that would also allow security guards to identify chemicals in a package without opening it. The research team made this laser-powered terahertz source and detector system work by funnelling the laser light to specifically selected locations near the terahertz antenna’s electrode. The laser light hitches a ride with free electrons on the surface of the metallic electrode. This forms a class of surface waves called surface plasmon waves. By coupling the beam of light with surface plasmon waves, the researchers created a funnel to carry light into nanoscale regions near the device’s electrodes.

‘With our higher-sensitivity terahertz system, you could see deeper into tissues or sense small quantities of illegal drugs and explosives from a farther distance. That's why it's important,’ said Mona Jarrahi. He is a University of Michigan assistant professor of electrical engineering and computer science and leader of the project.

Generating or detecting terahertz radiation requires the conversion of photons to electron hole pairs and their transfer into a device’s contact electrodes. Previously this process has been very inefficient, according to Jarrahi. But, his team designed a structure so that when photons land, most of them appear right next to the contact electrodes.

The research was funded by the Michigan Space Grant Consortium, the US government’s Defense Advanced Research Projects Agency, National Science Foundation, and Office of Naval Research and Army Research Office.