Snake like light beam propagation in Multimode Periodic Segmented Waveguide

In this article it is shown that for specific initial conditions an input beam injected in a Multimode Periodic Segmented Waveguides (MPSW) does not di ract and remains collimated all along the waveguide whereas a speckle like pattern is expected at the output of a multimode structure. This nonintuitive behavior can be explained with the help of ray and wave chaos properties. A modal analysis developed in this article reveals that this nondi ractive beam regime is due to a specific superposition of modes with regularly spaced propagation constants. A discrepancy with the commonly used Equivalent Continuous Waveguide model (ECWG) is also identied.