The phase-locked solid-state laser array presented in this proposal utilizes an external cavity to enforce phase locking in annular laser arrays. Our preliminary study done in a four-element quasi-cw laser array has achieved a stable and diffraction-limited operation in the fundamental mode at all powers with high efficiency. The proposed technique is applicable to two-dimensional arrays of fibers, rods, and slabs. The use of multiple concentric annular structures may further increase the number of elements in the array. In phase I, we will use an existing setup to demonstrate phase locking in a cw-pumped six-element laser array. This will enable us to evaluate the effects of random phase differences among the arrays. We will also demonstrate phase locking in a 12-element quasi-cw laser array and analyze the configuration of multiple concentric annular laser arrays. We will then design the 200-W class laser to be implemented in Phase II. We will identify the technological issues, and work out the solutions. The proposed high-power laser will find wide applications in material processing and surface treatments. When the phase-locking technology is combined with our monolithic pulsed laser technology, a compact phase-locked Q-switched laser array will find further applications in lidar and remote sensing applications
