The resonant nonlinear refraction of 4 – 5 μm light in CO and CO2 gas at a peak intensity of 15 MW/cm was demonstrated using timeand frequency-resolved measurements of self-focusing… Click to show full abstract
The resonant nonlinear refraction of 4 – 5 μm light in CO and CO2 gas at a peak intensity of 15 MW/cm was demonstrated using timeand frequency-resolved measurements of self-focusing and self-defocusing. The nonlinearity of these molecular gases exhibits intensity-dependent sign reversals and a < 4 ns response time. A change from selffocusing to self-defocusing or vice-versa was observed to occur for Rabi frequencies that are comparable to the collisional linewidth. A density matrix model for the nonlinear susceptibility of a strongly driven two-level system provides a qualitative explanation for
               
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