Self-influence of femtosecond laser pulse in a nonlinear nondispersive medium

With use of the method of multiple scales an analytic expression describing the amplitude of a femtosecond laser pulse with an arbitrary shape propagating in a nonlinear nondispersive medium in the approximation of small nonlinearity has been obtained taking into account the contribution of the nonlinearity of 5-th order. The running coordinates dependence of the carrier frequency of the pulse with the hyperbolic secant at the input has also been obtained. 7 refs