SATURATION EFFECTS IN DEGENERATE 4-WAVE-MIXING IN RUBY AND GDALO3-CR+3

In Cr+3-doped crystals the saturation of the excited-state population implies the saturation of the complex non-linear index of refraction n2, so n2 proportional-to (1 + I/I(s))-1. We developed a new theoretical model to calculate the efficiency of the degenerate four-wave mixing (DFWM) process in such a saturable nonlinear medium. Our experimental results in ruby and GdALO3:Cr+3 are in good agreement with the calculations of our theoretical model made using our previous interferometric measurements of n2 in these materials. In the GdAlO3:Cr+3 sample we obtained a maximum DFWM efficiency of approximately 10%, which to our knowledge is the highest value achieved in these kinds of material (Cr+3- or Nd+3-doped materials or organic dyes) with a cw laser.