Wednesday, February 20, 2008

Most Powerful Laser Ever

ScienceDaily reports on the most powerful pulsed laser ever built, a University of Michigan designed 300 terrawatt behemoth that beats any other laser in the world by two orders of magnitude in intensity and can fire every 10 seconds at a target just over a micron in diameter. A single terrawatt is the capacity of the entire US electrical grid, and a human hair is about 100 microns wide. However, the beam lasts only 30 femotseconds - 30 millionth of a billionth of a second. The laser could eventually be developed into medical applications such as cancer treatements, among others including fusion research. The researchers upgraded a former 50 terrawatt device by adding an additional amplifier to the already impressive HERCULES laser.

"HERCULES is a titanium-sapphire laser that takes up several rooms at U-M's Center for Ultrafast Optical Science. Light fed into it bounces like a pinball off a series of mirrors and other optical elements. It gets stretched, energized, squeezed and focused along the way.

HERCULES uses the technique of chirped pulse amplification developed by U-M engineering professor emeritus Gerard Mourou in the 1980s. Chirped pulse amplification relies on grooved surfaces called diffraction gratings to stretch a very short duration laser pulse so that it lasts 50,000 times longer. This stretched pulse can then be amplified to much higher energy without damaging the optics in its path. After the beam is amplified to a higher energy by passing through titanium-sapphire crystals, an optical compressor reverses the stretching, squeezing the laser pulse until it's close to its original duration. The beam is then focused to ultra-high intensity."

Basically, power is built up over a period then releases in an extremely powerful but short burst, comparable in intensity to all the sunlight striking the Earth focused onto a single grain of sand. Zoinks!

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