MEASUREMENT OF THE COEFFICIENT OF ELECTRONIC NONLINEARITY IN OPTICAL AND LASER GLASS.

The electronic nonlinearity coefficient n//2 of transparent dielectrics was determined by direct observation of the self-focusing of smooth single-mode nanosecond laser pulses. The critical self-focusing power for glass of a given type P//c//r was found from a series of measurements of the threshold power P//t//h for different effective specimen lengths L//e//f//f equals z//s//f, thus eliminating errors associated with the determination of the beam width. The required set of z//s//f values was obtained by varying the focusing or defocusing of the radiation on the entrance face of a single specimen. The experimental dependence of P**1**/**2//t//h on (z** minus **1//s//f), enabling P//c//r to be determined by the intercept on the ordinate axis, was only linear up to some value of P above which the regular self-focusing pattern was disrupted by the development of transverse perturbations. Data on P//c//r and n//2 were obtained for some Soviet glasses (KGSS 1621, GLS 1, LGS 247).