Nonlinear propagation of femtosecond optical pulses in fibers: contribution from frequency-dependent mode size

Abstract

We study nonlinear propagation of intense femtosecond pulses in a short single-mode optical fiber considering the fact that the mode size is frequency dependent. The importance of this effect has not been recognized to date. We include this effect in the nonlinear Schrodinger equation formalism by scaling the nonlinear interaction in a frequency-dependent manner. We evaluate this effect for parameters which are appropriate for compression of 40-fs input pulses to 8 fs or less1,2 and find that significant asymmetries result from this effect alone. We compare the magnitude of this correction with that of other corrections that have been investigated and find that it is one of the largest.