Z-SCAN MEASUREMENTS WITH FOURIER-ANALYSIS IN ION-DOPED SOLIDS

We report on the measurement of nonlinear refraction in ion-doped soli ds with a method that combines the single-beam Z-scan technique and a Fourier analysis of the transmittance time evolution. The laser beam i s modulated at a frequency f and the Fourier components at f and 2f ar e shown to be related, respectively, to Linear and nonlinear refractio ns, Their ratio is used to eliminate spurious Linear effects as a way of increasing the sensitivity of the measurement, with this method we are able to measure nonlinear phase changes of a few tens of mrad, cor responding to wave front distortions smaller than lambda/10(5). Moreov er, the technique can discriminate nonlinear processes with different relaxation times. (C) 1997 American Institute of Physics.