New nanotube coating enables novel laser power meter

WASHINGTON - Researchers at the National Institute of Standards and Technology (NIST) have developed a novel nanotube-coated power measurement device, which would be able to calibrate high-power laser systems, such as those intended to defuse unexploded mines, more quickly and easily.

The new laser power meter, tested at a U.S. Air Force base, 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 smaller-about 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 nanotubes, tiny cylinders made of carbon atoms, which 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.

The new power meter uses the latest version of NIST’s nanotube coating, which absorbs light efficiently, is more stable than some conventional coatings such as carbon black, and resists laser damage as effectively as commercial ceramic coatings.

NIST’s nanotube coating technology already has been transferred to industry for use in commercial products. (ANI)