Self-focusing of laser radiation caused by nonequilibrium vibrational excitation

The degree of self-focusing due to nonequilibrium vibrational excitation of molecules in a laser beam is estimated according to changes in the refractive index of the gaseous laser medium. Numerical results are obtained for the case of a CO2-N2 gas mixture which is heated by a laser pulse of 1 Joule at room temperature. It is shown that the time required for self-focusing to become significant is related to the pumping power, and is considerably less than the self-focusing time associated with kinetic cooling.