Researchers trap particle-based microlaser inside optical cable, a first

"This is the first demonstration of distributed sensing using a whispering gallery mode resonator," researcher Richard Zeltner said.
By Brooks Hays  |  March 20, 2018 at 2:05 PM
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March 20 (UPI) -- For the first time, scientists have trapped a particle-based microlaser inside an optical cable. The breakthrough could allow scientists to deliver laser light to hard to reach locations.

"The flying microlaser could potentially be used to deliver light inside the body," Richard Zeltner, researcher at the Max Planck Institute for the Science of Light in Germany, said in a news release. "By inserting a fiber into the skin, a microlaser emitting at a suitable wavelength could deliver precisely positioned light for use with light-activated drugs."

In experiments, scientists used the flying microlaser to make extremely precise temperature measurements in real time.

The technology utilizes a whispering gallery mode resonator, featuring particles that amplify specific wavelengths of light. Just as sound waves move across the curved surfaces of the whispering gallery in St. Paul's Cathedral, light waves ripple across the inner surface of the resonator particles.

"This is the first demonstration of distributed sensing using a whispering gallery mode resonator," said Zeltner. "This unique approach to sensing potentially opens many new possibilities for distributed measurements and assessing physical properties remotely with high spatial resolution. For example, it could be useful for temperature sensing in harsh environments."

The resonator is housed inside of a hollow-core photonic crystal fiber. The glass microstructure surrounding the hollow core confines light to the inside of the fiber.

"For quite some time, our research group has been developing the technology necessary to optically trap particles inside hollow-core photonic crystal fibers," said researcher Shangran Xie. "In this new work, we were able to apply this technology not just to trap a particle but also to induce it to act as a laser that can be used for sensing over long distances in a fiber."

Once the first laser microparticle is trapped inside the fiber, a second laser pulse is used to excite the microparticle, causing the microparticle to emit light. As the microparticle moves through the fiber, scientists can measure changes in its laser emissions. In experiments, researchers used the technology to measure changes in temperature as the microparticle moved through the fiber.

"The spatial resolution of this distributed sensor is ultimately limited by the size of the particle," said Zeltner. "This means that, potentially, we could achieve spatial resolution as small as several micrometers over very long measurement ranges, which is a huge advantage of our system compared with other types of distributed temperature sensors."

Scientists described the technology in a new paper published this week in the journal Optics Letters.

Topics: Max Planck
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