Brightly Colored Bird Feathers Inspire New Kind of Laser

A new kind of laser captures light just like some colorful bird feathers. The device mimics the nanoscale structure of colorful feathers to make high-intensity laser light with almost any color.
Lasers work by trapping light in or near a material that can emit more photons with the same wavelength, or color. Incoming photons excite the atoms in the material, and make them spit out more identical photons. But to get enough photons for a bright beam of laser light, the photons need to hang around in the material for a long time.
One way to buy time for photons is by forcing them to bounce back and forth. Traditional lasers do this by bouncing the photons between two mirrors. In recent years, physicists have built lasers from slabs of specialized glass with air holes drilled in them. Light can get trapped on a particular path between the holes, and bounce around long enough to make laser light.
Physicists have tried arranging the holes in both tightly ordered and completely random patterns. But both of those options had drawbacks — ordered lasers only work at one wavelength and are expensive to build, and random lasers aren’t very efficient.
Physicist Hui Cao of Yale and colleagues tried something in between: an arrangement of holes that looks random from afar but has pockets of order up close. This is similar to the setup of air pockets in bird feathers. Their results are published May 6 in Physical Review Letters.

Certain brightly colored birds, like kingfishers or parrots, have feathers embedded with a not-quite-random arrangement of air pockets. Wavelengths of light that are related to the distance between the air pockets get scattered and built up more than others, giving the feathers their characteristic colors.
“After we learned this, we said, ‘Oh, that’s a smart idea!’” Cao said. “Can we use this to improve our lasers? Maybe we can use short-range order to enhance light confinement and make lasing more efficient.”
Cao’s team drilled holes in a 190-nanometer-thin sheet of gallium arsenide, a special sort of semiconductor that transmits light efficiently and is commonly used in optics. The holes were spaced between 235 and 275 nanometers apart. The material included a layer of equally spaced quantum dots, which emit lots of light when struck with one photon. When light entered the material, the physicists reasoned, it should bounce around between the holes long enough to make the quantum dots produce enough photons to start lasing.

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