News in Science

Warships may deflect laser strikes

A material that shield ships against high-energy weapons like lasers is being developed by the US military.

The work, at the US Navy's China Lake Naval Warfare Center, could help protect equipment and personnel while advancing research in the world of metamaterials.

"If you have a ship being hit by a laser, and it was made of this metamaterial, you could reflect the laser beam," says Dr Simin Feng, one of the authors of the research published in Physical Review Letters.

Unlike normal materials, which derive their properties largely from the chemicals that comprise them, metamaterials are artificially made materials that get their properties from their physical structures.

The material Fend and her co-author Dr Klaus Halterman have theorised would be made of three layers of conventional materials, with the metamaterials sandwiched between the three layers.

Since the material would be thin it should be easily applied and "wouldn't weigh things down", says Halterman.

Metamaterials

There are several kinds of metamaterials.

Some, like the 'invisibility cloak' developed by Duke University researchers in 2006, channel certain wavelengths of light around a hidden object.

Others, like the navy's, have what is called a negative refractive index.

Stick a straw into a glass of water. The parts above and below the water point in slightly different directions. That's a positive refractive index, and is the case for nearly all materials.

A negative refractive index occurs if you try to stick the straw into the water and it bounces back at the exact but opposite angle it enters the water.

Now imagine the straw is instead a powerful laser. A ship made of conventional materials struck by such a laser would be sliced in half.

But a ship made with metamaterials would reflect the beam. And the more powerful the beam, the stronger the reflection would be, says Halterman.

Size matters

Like all optical metamaterials, their unique properties work only if the size of the structure is smaller than the wavelength of light being used.

Since the navy metamaterial would use very small structures it should repel nearly all lasers.

After publishing their work, Feng and Halterman were awarded a grant from the Office of Naval Research to turn their theory into reality.

Even with the money it will likely be a while before the laser-reflecting material works.

But if someone builds it, "it would be very interesting", says Dr Anthony Starr, president of SensorMetrix, a company that does metamaterial research. "A lot of possibilities would be raised. The trick would be making it."