A Novel Technique for Phase Locking a Very Large Number of Optical Fiber Amplifiers into a Single Coherent Array Dr. Thomas Shay University of New Mexico and Air Force Research Laboratory Optical fiber lasers are high efficiency, high brightness, and robust optical sources whose performance is relatively insensitive to mechanical and environmental disturbances. To achieve the high brightness required for many laser applications it is necessary to phase lock multiple element fiber optical amplifier arrays. The intensities and hence the powers available from single-mode optical fibers are limited by optical surface damage or nonlinear optical effects. These limitations can be overcome by coherent beam combining of the output power from multiple optical fibers. As a result of time-varying thermal loads and other disturbances, active feedback is required to provide for coherent addition of the beams from the array elements. We have invented the only electronic phase locking technique for coherent beam combination of optical amplifier arrays that doesn’t require an external reference beam. In this technique, an electronic control loop forces the optical phases of the array elements to self-synchronize. Both the theoretical analysis of novel method and results of optical fiber array beam combining experiments will be presented.