ABSTRACT
Nonlinear optical waveguides can behave quite differently from their linear counterparts as the field can manipulate itself via nonlinear interactions. Among various nonlinear optical waveguides, planar structures have been extensively investigated due to their ease of fabrication and analysis. The intensely self-focussed field will increase the local permittivity via the nonlinear interaction, and the increased permittivity will further focus and strengthen the local field. The self-focussing of the field, to the extent that the nonlinearity is no longer small, has a great bearing on all-optical switching and bistability. The number of nonlinear iterations required for solutions near the inflection point of the power dispersion curves is striking. The jump has been successfully explained and a useful bistability phenomenon in nonlinear optical channel waveguides has been identified. Contrary to one’s expectation, the self-focussing mechanism associated with weak nonlinear effects in a nonlinear planar structure is much more complicated than that in a nonlinear channel structure and is very difficult to characterise.
