Thermal self-defocusing of a CW CO2-laser beam during the interaction with water aerosol

The paper reports results of the measurement of the divergence of a CW CO2-laser beam propagating through an evaporating water aerosol. Bolometric sensors were used to determine the intensity distribution with respect to the beam cross section. It is shown that the divergence of a beam with a power of 170 W and a radius of 2 cm can increase by 0.001 rad on a path 3.6 m long when the initial optical density of the water aerosol is of the order of unity at a wavelength of 0.63 micron. Experimental results are compared with theoretical calculations of thermal self-defocusing in the thin-lens approximation.