Abstract

In waveguides with defocusing nonlinearity the effective refractive index (ERI) of guided modes decreases with mode’s power down to mode cutoff; they are not guided below certain value of mode’s power. In this work the ERI behavior near its cutoff value in self-defocusing nonlinear graded-index waveguides. These waveguides can be realized in strongly nonlinear materials. In the nonlinear graded-index waveguide the turning point of the guided mode and, hence, the size of the region, where the most part of power propagates, is changed with mode’s power. Radiation modes that are necessary in describing any radiation phenomena in the region around waveguide, and a dark fundamental wave at the smooth refractive index interface are also analyzed.

© 1996 IEEE