Diffraction Patterns Produced by Focused Laser Beams
Investigation of diffraction and jitter — two factors that influence the energy density produced by a laser beam projected from an aperture and focused onto a distant surface. The report first examines the characteristics of diffraction patterns produced by circular apertures with circular central obscurations and gaussian illuminations. Formulas, tables, and graphs are presented that enable the reader to estimate the peak intensity, the spot size, the power within the spot, and the average intensity over the spot that can be achieved by a given laser/telescope system. Attention is then directed to the problem of estimating energy densities when the center of the diffraction pattern jitters about an aim point on the target. A method is presented for estimating the effect of jitter that depends, in part, on approximating a real diffraction pattern with a gaussian pattern.