Laser beam combining for power and brightness scaling

An attractive approach for building high-power laser systems is to use laser arrays with many lower power array elements. In order to achieve high brightness from these laser arrays, beam combining techniques must be employed. We are developing a beam combining technique, spectral beam combining, which is robust and has the potential to beam combine arrays with many array elements. In spectral beam combining, the various laser array elements operate at slightly different wavelengths which an then spatially overlapped. We have made proof-of-principle demonstrations of spectral beam combining on one-dimensional laser arrays with fiber and with semiconductor array elements and shown beam combining of up to 11 array elements in these initial experiments. Simple scaling laws dictate that the maximum number of gain elements in the array is proportional to the available optical gain bandwidth and the size of the system. Using typical numbers for fibers and diode arrays, it can be shown that it should be possible to combine 10's to 100's of array elements. Experiments to scale the number of array elements, understand key issues such as cross-talk, and increase efficiency are on-going.