An experimental study of self-focusing and self-defocusing of a TEA CO2 laser pulse in CDF3

We observed self-focusing and self-defocusing of a TEA CO₂ laser pulse in CDF₃ vapor under different conditions. The experimental parameters we varied are the pressure inside the interaction cell, the frequency of the laser, the energy 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 intensity of the laser pulse. We propose a physical model that can explain these experimental results. This model is different from that used to explain the selffocusing of a CO₂ laser in SF₆.