APPARATUS FOR STUDY OF REFRACTIVE-INDEX NONLINEARITY OF OPTICAL-MATERIALS WITH PICOSECOND LIGHT-PULSES

The authors describe a measuring complex for study of the refraction nonlinearity of optical media by an interference method and a "nonlinear-lens" method in the field of light pulses from a passively mode-locked YAG:Nd3+ laser. The accuracy of relative measurements of refraction nonlinearity by the interference method is analyzed. Measurement results are given for the coefficients of refractive-index nonlinearity of potassium-gadolinium tungsten (PGT) with respect to carbon bisulfide. It is noted that, despite a record-high coefficient of nonresonance refraction nonlinearity for laser crystals of (1.2 +/- 0.2) 10(-20) m2/V, the filamentary fractures that are typical of self-focusing are not observed in PGT at light-power densities of up to 20 GW/cm2, and the absence of self-focusing correlates with the forced combination scattering in the specimens.