The dream of intensifying light is as old as civilization. Legend has it that Archimedes focused the sun’s rays with a giant mirror to set the Roman fleet afire at Syracuse in 212 B.C. Although that story is a myth, it is true that around 200 B.C. another Greek, Diocles, had invented the first ideal focusing optic, a parabolic mirror. Two millennia later mirrors and quantum mechanics were put together to make the most versatile of high-intensity light sources: the laser.
The epitome of high-power lasers is Nova, which operated at Lawrence Livermore National Laboratory from 1985 to 1999. Named for the brilliance of an exploding star, Nova was one of the largest lasers ever built. Ten parallel chains of laser amplifiers occupied a 300-foot enclosure; mirrors made from 400-pound blocks of glass directed the beams to targets for nuclear fusion and other experiments. Nova was fired no more than a few times each day to avoid overheating. Clearly, it marshaled a lot of energy to achieve its ultrahigh power.
Yet power is the rate at which energy is delivered, so another approach to ultrahigh power is to release a modest amount of energy in an extremely short time. Nova’s usual pulses were relatively long by the standards of today’s ultrafast lasers—three nanoseconds—and each one required kilojoules of energy. By using pulses of one ten-thousandth their durations, a new type of laser that fits on a tabletop can deliver power similar to Nova’s [see “Ultrashort-Pulse Lasers: Big Payoffs in a Flash,” by John-Mark Hopkins and Wilson Sibbett; Scientific American, September 2000]. For example, an ultrahigh-power laser that delivers a mere joule in a pulse lasting 100 femtoseconds (10–13 second) achieves 10 trillion watts (1013 W, or 10 terawatts), more than the output of all the world’s power plants combined.
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