Researchers from the University of Michigan have developed a small device that can bend light to create radiation. The match-head sized device bends light inside a crystal to generate synchrotron radiation in a lab.
The device created by the University of Michigan team bends visible light to produce light with a wavelength in the terahertz range. This range is larger than visible light but smaller than the waves produced by a microwave.
Scientists shrink process down drastically
Usually, this kind of procedure is done in very large facilities. But Roberto Merlin and Meredith Henstridge’s working with their team managed to shrink it down.
The new tiny device includes a printed pattern of microscopic gold antennae on the polished face of a lithium tantalate crystal, called a metasurface. Light was then pulsed through the pattern of antennae, which bent the light and produced synchrotron radiation.
“Instead of using lenses and spatial light modulators to perform this kind of experiment, we figured out by simply patterning a surface with a metasurface, you can achieve a similar end,” said Roberto Merlin, professor of physics and electrical engineering and computer science.
“In order to get light to curve, you have to sculpt every piece of the light beam to a particular intensity and phase, and now we can do this in an extremely surgical way.” The metasurface is made up of 10 million tiny curved-shaped antennae, which are much smaller than the impinging light.
Researchers hope to further develop device
A laser that produces super short bursts of light is directed towards the antennae where it is moved to accelerate along the curved trajectory inside the crystal. Currently, the device produces synchrotron radiation that contains many terahertz frequencies because the light pulses travel just a fraction of a circle.
The University of Michigan team which included researchers from Purdue University, hope to further refine the device so that the light pulse revolves continuously along a circular path, producing synchrotron radiation at a single terahertz frequency. Single-frequency terahertz sources are used by scientists to study the behavior of atoms or molecules within a given solid, liquid or gas.
Commercial applications of the technology are used to scab for items hidden in clothing and packaging crates. Items that need to be identified such as drugs, explosives, and toxic gases have an identifying ‘fingerprint’ visible under terahertz spectroscopy.
But the use of the new device extends beyond the security industry. “Terahertz radiation is useful for imaging in the biomedical sciences,” Meredith Henstridge said. “For instance, it has been used to distinguish between cancerous and healthy tissue. An on-chip, single-frequency terahertz source, such as a tiny light-driven synchrotron such as our device, can allow for new advancements in all of these applications.”
The study was published in the journal Science. Fellow Purdue researchers are Vladimir Shalaev, Di Wang and Alexandra Boltasseva.