Abstract

Kink, or optical shock solitons, have been discussed for propagation under the influence of the Raman effect [1,2,3]. Here we show that these types can still exist when we allow for a parabolic nonlinearity. The nonlinearity function N(I) indicates how the refractive index of an optical waveguide increases with intensity, I. The ‘parabolic’ nonlinearity [4,5], N(I) = I - vl², where v is a free parameter, can be obtained by using two dopants, with one being self-focusing and the other self-defocusing [6]. It has been shown [3] that kink type solitons can exist where there Raman delay is not negligible. In the time domain, this represents the fact that the glass response to the imposed field is not instantaneous. This delay of a few fs can affect propagation of fs signals. In the frequency domain, the effect is a continuous downshift of frequency. even in the perturbation range, this causes the usual pulse-type solitons.

© 1996 Optical Society of America