New nanotube coating enables novel laser p...( The U.S. military can now calibrate ...)

The U.S. military can now calibrate high-power laser systems, such as those intended to defuse unexploded mines, more quickly and easily thanks to a novel nanotube-coated power measurement device developed at the National Institute of Standards and Technology (NIST).

The new laser power meter, tested at a U.S. Air Force base last week, will be used to measure the light emitted by 10-kilowatt (kW) laser systems. Light focused from a 10 kW laser is more than a million times more intense than sunlight reaching the Earth. Until now, NIST-built power meters, just like the lasers they were intended to measure, were barely portable and operated slowly. The new power meter is much smallerabout the size of a crock pot rather than a refrigerator. It also features a new design that enables it to make continuous power measurements.

A key innovation is the use of a sprayed-on coating of carbon nanotubestiny cylinders made of carbon atomswhich conduct heat hundreds of times better than conventional detector coating materials.

In the new power meter, laser light is absorbed in a cone-shaped copper cavity, where a spinning mirror directs the light over a large area and distributes the heat uniformly. The cavity is lined with a NIST-developed coating made of multiwalled carbon nanotubes held together by a potassium silicate (water glass) binder, and surrounded by a water jacket. The coating absorbs light and converts it to heat. The resulting rise in water temperature generates a current, which is measured to determine the power of the laser.

NIST has developed and maintained optical power standards for decades. In recent years, NIST researchers have experimented with a variety of coatings made of nanotubes because they offer an unusual combination of desirable properties, including intense black color for maximum light absorption. Designing a detector to collect and measure all of the power from a laser intended to significantly alter i
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