Oscillatory beam quality effects in modular high energy laser systems

The amplitude of the major phase distortions in in-line modular chemical laser systems increases linearly with the number of modules. The beam quality of a model modular linear-gain laser has been examined as a function of the amplitude of the phase distortion by propagating the distorted output beams to a distant focus using the Lincoln Laboratory laser propagation code. Oscillations are observed in both the peak intensity and the far field area containing 63% of the laser flux. The observed oscillatory behavior is not strongly dependent on the shape of the phase distortion. The implications of this behavior for modular laser design are discussed and extended to modular annular gain lasers.