Beam steering via peak power decay in nonlinear waveguide arrays

We report the experimental observation and theoretical analysis of a novel beam-steering effect in periodic waveguide arrays that arises from the interplay between discrete diffraction, Kerr nonlinearity and any mechanism that effectively weakens the nonlinear part of the beam. In this regime the propagation direction shows increased sensitivity to the input angle and for a certain angular range around normal incidence a nonlinear beam may be guided to a direction opposite to that initially inserted. For continuous wave beams the role of this mechanism is played by absorption of any kind, such as three photon absorption, two photon absorption or even linear absorption. For pulsed beams we show that the same dynamics can arise due to strong normal temporal dispersion, while absorption is not necessary and can be a further enhancing or alternative factor. This observation falls under a more general dissipation-assisted beam velocity control mechanism in nonlinear optical lattices, which is also theoretically predicted by the effective particle approach.