Reduction of Thermal Blooming by Beam Optimization.

The report examines various techniques for reducing the severe thermal distortion effects which represent a serious limitation for high power CO2 laser beams in the atmosphere. The principal accomplishments reported here are in the areas of 1 beam amplitude and phase shaping for reducing cw thermal blooming effects, and 2 the investigation of multiple pulse or pulse train propagation as a means for alleviating the thermal blooming problem. In Section II the studies of beam optimization for cw propagation are discussed. Numerical calculations of the thermal blooming were used to investigate a the effects of beam amplitude shaping, and b a reciprocity approach for establishing the optimum beam amplitude and phase shape.