Random Laser Control
Tony Pallone | October 27, 2017
A new type of optical fiber is capable of controlling random lasers. Image credit: University of New Mexico.
At their most basic level, lasers work by optical amplification of electromagnetic radiation. Energy is pumped into a gain medium – a material with properties that allow it to amplify light. Lasers commonly employ a pair of mirrors to create a resonating cavity that bounces light back and forth through the gain medium; the light gets amplified with each bounce, producing an intense beam.
There are also random lasers that use no resonating cavity, and a highly-disordered gain medium. On the bright side (no pun intended), they possess broad spectral features; a random laser can produce a beam of light containing multiple spectra, which is highly useful for applications such as biomedical imaging. But with their multi-directional output and chaotic fluctuation, they are difficult to reliably control.
Researchers at the University of New Mexico (UNM), however, have been able to overcome these obstacles by fabricating an optical fiber made of satin quartz – a highly porous artisan glass typically used to calibrate fiber-optic machinery. By pulling the material into long rods, dozens of microscopic air channels are created in each fiber.
Then a little bit of condensed matter physics comes in: the optical fiber produces a phenomenon known as Anderson localization, which causes free electrons to follow a single, looped path.
“Those holes in the glass are actually creating the channels that control the laser," explains Behnam Abaie, a Ph.D. student at UNM’s Center for High Technology Materials (CHTM). "The glass that we're using for these fiber optics is actually material that we would typically throw away.”
The research is published in a recent issue of Light: Science & Applications.
“Our device has all the great qualities of a random laser, plus spectral stability and it is highly directional," adds Arash Mafi, interim director of CHTM.
Mafi and his team are some of the leading experts in the Anderson localization phenomenon; an article they published in 2014 was named one of Physic World’s Top Ten Breakthroughs of the Year.
"There is still a lot to learn about Anderson localization but it's exciting for us to be part of this development," Mafi continues. "To be able to actually make devices that utilize this phenomenon (is) taking the science to yet another level."
