Self-Focusing And Self-Defocusing Of A Tea Co2 Laser Pulse In CDF3 Vapor

We observed self-focusing and self-defocusing of a TEA CO2 laser pulse in CDF3 vapor under different conditions. The experimental parameters that we varied are: the pressure inside the interaction cell, the frequency of the laser line, the intensity and the temporal length of the pulse. We have shown that it is possible to pass from self-focusing to self-defocusing by only increasing the energy of the laser pulse of a fixed temporal length. We propose a physical model using the selection rule of the molecular transition that can explain these experimental results.