Did you watch those superhero cartoons as a kid? The ones where the supervillain had a crazy plan to destroy the world every week and at least half of them used a giant mirror to reflect a powerful ray gun? (Doctor Horrible anyone…) Well, the supervillain mirror is now a possibility.
High-power lasers shoot a continuous beam of light and are strong enough to cut steel, precise enough to perform surgery, and powerful enough to carry messages into deep space. What’s difficult is to engineer resilient and long-lasting components that control the powerful beams the lasers emit.
Most mirrors that direct the beam in high-power continuous wave (CW) lasers are made by layering thin coatings of materials with different optical properties. But if there is just one tiny defect in any of the layers, the powerful laser beam will burn through, causing the whole device to fail.
Researchers at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) built a mirror out of diamond. By etching nanostructures onto the surface of a thin sheet of diamond, the research team created a highly reflective mirror that withstood, without damage, experiments with a 10-kilowatt Navy laser.
They published their research in Nature Communications.
Loncar’s Laboratory for Nanoscale Optics originally developed the technique to etch nanoscale structures into diamonds for quantum optics and communications applications. Using this technique, which uses an ion beam to etch the diamond, the researchers sculpted an array of golf-tee-shaped columns onto the surface of a 3-millimeter by 3-millimeter diamond sheet. The shape of the golf tees, wide on top and skinny on the bottom, makes the surface of the diamond 98.9% reflective.
The mirror had to be tested in a specially designed locked room to prevent dangerous levels of laser light from seeping out and blinding or burning those in the adjacent room. They put their mirror in front of a 10-kilowatt laser—one strong enough to burn through steel. The mirror emerged unscathed.