Every car, train and plane built since 1970 has been manufactured using high-power lasers that shoot a continuous beam of light. The lasers are strong enough to cut steel, precise enough to perform surgery, and powerful enough to carry messages into deep space. It is difficult to engineer components that can control the powerful beams of the lasers because they are so powerful.
Most mirrors used to direct the beam in high-power continuous wave (CW) lasers are made by layers of thin coating materials with different optical properties. The whole device will fail if there is one tiny defect in any of the layers.
If you could make a mirror out of a single material, it would greatly reduce the chance of defects and increase the lifespan of the laser. What material would be strong?
The Harvard John A. Paulson School of Engineering and Applied Sciences has built a mirror out of one of the strongest materials on the planet. The research team built a mirror that was impervious to damage after etching nanostructures onto the surface of a thin sheet of diamond.
"Our one-material mirror approach eliminates the thermal stress issues that are detrimental to conventional mirrors, formed by multi-material stacks, when they are irradiated with large optical powers," said Marko Loncar, the Professor of Electrical.
The research is in Nature Communications.
The technique to etch nanoscale structures into diamonds was originally developed by Loncar.
"We thought, why not use what we developed for quantum applications and use it for something more classical?" said the first author of the paper.
The researchers sculpted an array of golf-tee shaped columns on the surface of a 3-milimeter by 3-milimeter diamond sheet using this technique. The shape of the golf tee makes it 98.9% reflective.
Neil Sinclair, a research scientist at SEAS and co-author of the paper, said that reflectors that are 99% reflective are fine for low power laser but wouldn't be able to survive high powers.
To test the mirror with a high-power laser, the team turned to the Pennsylvania State University Applied Research Laboratory, a Department of Defense designated U.S. Navy University Affiliated Research Center.
There is a locked room with a mirror in front of a 10 kilo watt laser that is strong enough to burn through steel.
The mirror was undamaged.
The selling point of this research is that we had a 10-kilo watt laser focused down into a 750-micron spot on a 3-by-3- millimeter diamond, which is a lot of energy focused down on a very small spot, and we didn't burn it.
In the future, these mirrors could be used for defense applications, Semiconductor manufacturing, industrial manufacturing, and deep space communications. The approach could also be used in less expensive materials.
The intellectual property associated with this project has been protected by Harvard OTD.
More information: Haig A. Atikian et al, Diamond mirrors for high-power continuous-wave lasers, Nature Communications (2022). DOI: 10.1038/s41467-022-30335-2 Journal information: Nature Communications Citation: Diamond mirrors for high-powered lasers (2022, May 23) retrieved 23 May 2022 from https://phys.org/news/2022-05-diamond-mirrors-high-powered-lasers.html This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.
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