Discover Magazine has an article about the world's largest laser, currently nearing completion at the National Ignition Facility in Livermore, California. The laser, which has already shown the ability to fire four megajoules of infrared energy for up to 20 nanoseconds, is intended for fusion research.
The goal is to fire the powerful laser into both ends of a tiny gold capsule filled with two frozen hydrogen isotopes. The blast will create a plasma around the target in the center of the capsule, hopefully hot enough to cause the two hydrogen isotopes to fuse.
The researchers are currently testing the optics and expect to complete construction of the laser by March of next year. By 2010, they expect to reach a point where the fusion energy produced by the machine is greater than the energy used by the lasers, creating a net-positive energy fusion reaction.