Light-Based Tech to Navigate the Moon

RMIT University, Melbourne, and University of Adelaide, Australia

RMIT University’s Arnan Mitchell and University of Adelaide’s Dr. Andy Boes led an international team to review lithium niobate’s capabilities and potential applications in the journal Science. The team is working to make navigation systems that help rovers drive on the Moon — where GPS is unable to work — later this decade.

By detecting tiny changes in laser light, the lithium-niobate chip can be used to measure movement sans external signals, Mitchell noted.

“This is not science fiction — this artificial crystal is being used to develop a range of exciting applications,” said Mitchell. “And competition to harness the potential of this versatile technology is heating up.”

“Our lithium niobate chip technology is also flexible enough to be rapidly adapted to almost any application that uses light,” he added. “We are focused on navigation now, but the same technology could also be used for linking internet on the Moon to the internet on Earth.”

Lithium niobate is an artificial crystal first discovered in 1949.

“Lithium niobate has new uses in the field of photonics — the science and technology of light — because unlike other materials it can generate and manipulate electro-magnetic waves across the full spectrum of light, from microwave to UV frequencies,” Boes said. “Silicon was the material of choice for electronic circuits, but its limitations have become increasingly apparent in photonics.

“Lithium niobate has come back into vogue because of its superior capabilities, and advances in manufacturing mean that it is now readily available as thin films on semiconductor wafers.”

A layer of lithium niobate, about 1,000 times thinner than a human hair, is placed on a semiconductor wafer, Boes said. “Photonic circuits are printed into the lithium niobate layer, which are tailored according to the chip’s intended use. A fingernail-sized chip may contain hundreds of different circuits,” he said.

The team is working with Australia-based Advanced Navigation to create optical gyroscopes, in which laser light is launched in both clockwise and counter-clockwise directions in a coil of fiber, Mitchell noted.

“As the coil is moved, the fiber is slightly shorter in one direction than the other, according to Albert Einstein’s theory of relativity,” he said. “Our photonic chips are sensitive enough to measure this tiny difference and use it to determine how the coil is moving. If you can keep track of your movements, then you know where you are relative to where you started. This is called inertial navigation.”

According to Mitchell, the technology can also be used to remotely detect the ripeness of fruit, as gas emitted by ripe fruit is absorbed by light in the mid-infrared part of the spectrum.

“A drone hovering in an orchard would transmit light to another which would sense the degree to which the light is absorbed and when fruit is ready for harvesting,” he said. “Our microchip technology is much smaller, cheaper, and more accurate than current technology and can be used with very small drones that won’t damage fruit trees.”

“We have the technology to manufacture these chips in Australia and we have the industries that will use them,” Mitchell said. “Photonic chips can now transform industries well beyond optical fiber communications.”

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