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.