Building the World's Most Powerful Laser

This March, researchers at the National Ignition Facility demonstrated a 1.1 megajoule laser designed to ignite nuclear fusion reactions by 2010. But the facility's technology, which is housed at the Lawrence Livermore National Laboratory in California, cannot yet generate enough energy to drive a practical power plant. So, even as physicists look forward to next year's demonstration, they're working on even more powerful lasers that could make possible a method for a kind of laser-induced fusion called fast ignition.
This week, at the annual meeting of the Optics Society of America in San Jose, CA, researchers from the University of Texas presented plans to build an exawatt laser that would be three orders of magnitude more powerful than anything that exists today. Today's most powerful lasers operate on the order of about a petawatt, or 10 to the power 15 (one quadrillion) watts. An exawatt is 10 to a power of 18 watts. Exawatt lasers will be able to concentrate that power in areas measuring micrometers, creating tremendous intensities.

One way to increase the power of a laser is to decrease the duration of the laser pulse. But working with laser pulses on the order of picoseconds or even femtoseconds is difficult because such pulses are made up of a wide bandwidth of light frequencies that damage optical glass, including the phosphate glass often used to amplify laser light, for example at the National Ignition Facility.

Todd Ditmire, director of the High Intensity Laser Science Group at the University of Texas at Austin, reported at this week's meeting that a new type of glass should be able to handle the intense pulses of light needed to create an exawatt laser. The glass would be doped and used to create devices called amplifiers--when light from a laser shines on the glass amplifier, ions in the glass absorb the light and re-emit it at higher energy. "The glass is just a host--it's a transparent material that holds the ions," says Ditmire.