The Effects of Step Bulk Arrangement in Propagation of High-power Laser Beam in Atmosphere

We have designed an arrangement of 19 high-power fiber laser collimators on an aluminum step bulk, theoretically to coherently combine and use in directed energy applications. The propagation conditions for high-power laser beam have been investigated in this work. Laser beam propagating undergoes unavoidable spreading and wondering because of laser beam's inherent and environmental conditions which affect power density and propagation efficiency on target. We have used the beam spreading factors classification to diffraction limited, beam quality, and atmosphere turbulence to calculate the related effects. Diffraction-limited beam spreading is dependent with initial beam radius where it is degraded by growing it up. The second affecting parameter is beam quality factor where it will be ignored for single-mode laser beam (M-2 = 1). The most important one is atmosphere turbulence and defined as the refractive index structure constant, C-n(2) and based on, it would be categorized as weak, moderate, and strong turbulences. On the other hand, the deep turbulences make more spreading and wondering of long distance laser beam propagation where it concludes to low power density on target. Although adaptive optics could be used to adjust and moderate the atmosphere perturbation effect, it has no impact to low-quality laser beam.