Method for Estimating the Thermal Blooming Effect
Describes a simple method without the use of codes which has been developed to estimate the thermal blooming of a high-power focused laser beam propagating through an absorbing medium. Continuous wave laser beam propagation through an absorbing medium heats the medium along the path of the beam; the heating of the medium then induces a local change in the index of refraction of the medium which, in turn, causes some effects of spreading, distorting, bending, or defocusing of the beam. These are known as thermal blooming or thermal lensing effects. One important consequence of these effects is to spread the laser beam over a larger area, thereby reducing the intensity incident on a target. The method described in this report permits the approximate estimation of the reduction of laser intensity on the target, but not the detailed intensity pattern caused by the thermal blooming effect.