Phase-Locked Amplifier Arrays Pave the Way for Fiber Laser Weaponization

  • Published
  • By Mary Rodriguez
  • AFRL/RD
KIRTHLAND AIR FORCE BASE, N.M. --  In a substantial step towards realizing weapons-class fiber lasers, AFRL researchers successfully phase-locked five 145 W amplifier chains, obtaining a total laser power output of 725 W. Achieved via the lab's coherent beam combination technique known as LOCSET, the Locking of Optical Coherence by Single-Detector Electronic-Frequency Tagging, this milestone constitutes a new world record on two counts: most power obtained from an electronically phase-locked fiber amplifier array, as well as from any coherent fiber laser combination method. The measured root-mean-square phase error theoretically predicts an array Strehl ratio of 0.99, which indicates excellent overall laser beam quality. This accomplishment marks critical progress in the quest to put high-power laser systems on relatively small, mobile platforms, including unmanned air vehicles and fighter aircraft.

High-power electric lasers are a key technology for weaponizing lasers of the future. LOCSET employs an approach similar to that of combining several optical mirrors into a single, larger, more effective one (as used in many modern astronomical telescopes). Specifically, LOCSET facilitates the merger of numerous, lower-power lasers into one, more powerful laser. While many challenges arise from this technique, the resulting technology's potentially enormous payoff warrants its pursuit.

The phase-locked amplifier experiment produced results surpassing two key thresholds--individual element power and overall device output power. This outcome, which translates to a newfound capacity for overall output power in the kilowatts range, represents perhaps the most crucial of all advances in the drive to transition the technology to weapons-class status.

Future experiments will involve scaled-up power for both the elements and the device, while also addressing such aspects as overall size, packaging, cooling requirements, and efficiency. Just as the chemical oxygen-iodine laser was ultimately viewed as having precipitated the Airborne Laser program, so too may this groundbreaking, vital technology one day be perceived as having catalyzed the emergence of high-power electric lasers.