Blackbody swallows laser light.

Blackbody swallows laser light

People working with lasers in laboratories face various hazards from the light. Laser light reflected off the components of whatever apparatus is being used can damage the lens of the eye as well as structures in the back of the eye. It can produce third-degree burns on the skin, damage walls and furniture and even start fires. All these problems were dramatically illustrated in a series of slides shown by Chongwen Guan of the Shanghai (China) Institute of Optics and Fine Mechanics. Furthermore, he says, a psychological survey showed that workers in such laboratories are often reluctant or negligent about using protective goggles.

Therefore, researchers at the institute have developed another form of protection, a "laser safeguard" that uses a kind of blackbody to swallow the reflected light.

The textbook variety of blackbody is a round, dark object, rather like a potbellied stove, with a source of energy inside it. The energy does not escape from the stove; it gets reflected back and forth inside the stove until it is thoroughly smooth and homogenized. Observers inside the blackbody would see radiation representing a single temperature coming at them from all directions. The outside world would not know a blackbody was there unless a small hole in it let a little of its characteristic radiation out.

The Shanghai "laser safeguard" -- a tabletop blackbody that is spherical or polyhedral in shape -- reverses the process. An opening in the device, which is placed where the reflected laser beam will enter, allows light into the blackbody. Inside the blackbody the light is trapped bouncing back and forth from wall to wall. On each bounce, some of it is absorbed by a coating on the inside of the blackbody, and so it is gradually suppressed.