Resonant mode flopping in modulated waveguiding structures

We put forward the concept of resonant, Rabi-like flopping and adiabatic transitions between confined light modes in properly modulated multimode waveguides. The phenomenon is shown to take place in both, the linear and the nonlinear regimes. In addition, we find that the mode transitions occur not only in simple geometries, but also in complex confining multimode structures. The phenomenon is analogous to the familiar stimulated state transitions that occur in multilevel quantum systems.