Nonlinear surface waves in curved waveguide arrays

In this work, we study, for the first time to our knowledge, the interplay between both types of localized surface modes at the edge of a semi-infinite periodically curved waveguide array with a surface defect. We demonstrate experimentally the signature of such modes, and show that nonlinear beam self-action can provide effective control and switching between different surface states. For experimental investigations, the light from a cw laser (lambda= 532 nm) is focused to different waveguides of the array and the output intensity distribution is recorded on a CCD camera. When the input beam is coupled to the second waveguide, we observe that the output beam position shifts depending on the bending amplitude. This is a signature of beating between the different types of linear surface modes. At high input power, nonlinear coupling and interaction occurs between different surface modes. This can lead to switching of the output beam position from the first to the second and then back to the first waveguide as we increase the power. Our results suggest novel opportunities for all-optical control of surface waves and surface probing applications.