Refining the Beam on Lasers

Single-frequency amplifiers are being developed for the Defense Advanced Research Projects Agency's (DARPA's) new Revolution in Fiber Lasers program. The program is designing building blocks to combine laser beams that can be scaled to a weapons-class power level while maintaining good beam quality. Fiber lasers are 1.5 to 2 times more efficient than solid-state lasers. Today, single-frequency fiber lasers and amplifiers are limited to several hundred watts because of stimulated Brillouin scattering. The scattering reflects power backward and damages low-power components. A Northrop Grumman-led team, which received a $4.5 million contract to work on the project, plans to use proprietary methods to eliminate the scattering. Goals of the DARPA project include demonstrating single-frequency fiber amplifiers at 1 kilowatt during the first phase of the contract and 3 kilowatts by the end of the second phase.