An ultrasound detector to help spot weapons

Airport security may soon get a boost as scientists have now developed a unique terahertz detector and imaging system that could could convert light to sound.

"We convert the T-ray (terahertz radiation) light into sound," said Jay Guo, a professor at University of Michigan.

"Our detector is sensitive, compact and works at room temperature, and we have made it using an unconventional approach," Guo added.

The so-called T-rays, which are light waves too long for human eyes to see, could help airport security guards find chemical and other weapons.

They might let doctors image body tissues with less damage to healthy areas.

They could also give astronomers new tools to study planets in other solar systems.

Because terahertz frequencies fall between the capabilities of the specialised tools presently used to detect light, engineers have yet to efficiently harness them.

The new detector could bridge this terahertz gap.

"The terahertz gap is a sliver between the microwave and infrared bands of the electromagnetic spectrum-the range of light's wavelengths and frequencies," the study noted.

Here is how it works.

When the terahertz light hits the transducer, the nanotubes absorb it, turning it into heat. They pass that heat on to a mixture of a spongy plastic called polydimethylsiloxane, or PDMS.

The heated PDMS expands, creating an outgoing pressure wave. That is the ultrasound wave. It is more than 1,000 times too high for human ears to pick up.

The response speed of the new detector is a fraction of a millionth of a second, which Guo says can enable real-time terahertz imaging in many areas, researchers concluded.