AFRL Records Highest Output Power Ever for Coherently Combined Array of Fiber Lasers Published July 22, 2014 By Jeanne Dailey Directed Energy KIRTLAND AIR FORCE BASE, New Mexico -- The Directed Energy Directorate's Laser Division has successfully combined multiple continuous-wave low-power fiber laser beams into a single coherent kilowatt (kW) class high-power beam using patented technology called Locking of Optical Coherence by Single-detector frequency Tagging (LOCSET). LOCSET is an enabling technology that allows precise target engagement while minimizing collateral damage. Combining multiple low-power lasers with good beam quality into one high-power beam helps in overcoming power limitations of fiber lasers. The Laser Division's Advanced Electric Lasers Branch coherently combined 16 narrow linewidth 90W lasers arranged in a two-dimensional 4x4 laser array into a single kW level (1.45kW) laser beam. The results represent the highest output power ever recorded for a coherently combined array of fiver lasers. Successful development of laser weapons is expected to have a vast impact for future military and directed energy applications. As such, fiber lasers offer several mission-critical advantages over traditional chemical and solid-state lasers, including compactness, excellent beam quality, and superior thermal-optical properties. Presently, the power available from single mode optical fibers is limited by surface damage, thermal loads, and nonlinear optical effects. As a result, beam combining techniques such as AFRL's LOCSET have been actively researched. LOCSET is a well-established scheme that was successfully employed by contractors such as Northrop Grumman, Lockheed Martin, and Raytheon for beam combination. Notably, the recent high-power experiments establish LOCSET's viability at kilowatt power levels. In addition, because of LOCSET's high-operational bandwidth, low-phase error and narrow linewidth of the lasers, LOCSET appears readily scalable for efficient combination of over 100 lasers.