A new diamond mirror can withstand a 10-kilowatt Navy laser beam

Are diamond mirrors forever?

Researchers from the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) built an incredibly durable mirror out of diamonds that can harness the immense power of high-power continuous wave (CW) lasers, a press statement reveals.

It could lead to new state-of-the-art applications in semiconductor manufacturing and deep-space communications.

A new type of one-material mirror

High-powered lasers play an integral part in the manufacturing process of the vast majority of cars, trains, and aircraft, but it's difficult to build durable, long-lasting components to control these incredibly powerful lasers that are capable of cutting through steel.

Most mirrors used today to direct laser beams in CW lasers are made by layering thin materials with different optical properties. Even the slightest defect in one of these layers will typically cause the powerful laser to burn through the materials, causing the system to fail.

Now, the Harvard researchers have detailed their new mirror built only using diamond in a paper published in Nature Communications. Their new type of mirror greatly reduces the likelihood of defects as it is made only using one material, and it should also have a greatly increased lifespan due to the strength of the material.

"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 Tiantsai Lin Professor of Electrical Engineering at SEAS and senior author of the paper. "This approach has the potential to improve or create new applications of high-power lasers."

New diamond mirror withstands 10-kilowatt Navy laser

In experiments, the researchers said their diamond mirror withstood experiments with a 10-kilowatt Navy laser without taking any damage. The technique used for the new mirror was originally designed to etch nanoscale structures into diamonds for use in quantum optics. The researchers used this method to etch golf tee shaped columns on the surface of a 3-milimeter by 3-milimeter diamond sheet. The golf tee shape was used because it makes the surface of the diamond 98.9 percent reflective, the Harvard team explained.

"The selling point with this research is that we had a 10-kilowatt 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," said Haig Atikian, a former graduate student and postdoctoral fellow at SEAS and first author of the paper. "This is important because as laser systems become more and more power hungry, you need to come up with creative ways to make the optical components more robust."

The researchers hope that in the future their mirrors could be used for semiconductor manufacturing, defense applications, and deep-space communications, among a number of other applications.