Observation of Rotation-Induced Light Localization in Waveguide Arrays

Westudy both experimentally and theoretically the propagationof light in the fs-laser written rotating square waveguide arraysand present the first experimental evidence of light localizationinduced by the rotation of periodic structure in the direction oflight propagation. Such linear light localization occurs either inthe corners of truncated square array, where it results from the interplaybetween the centrifugal effect and total internal reflection at theborders of truncated array, or in the center of array, where rotationcreates effective attractive optical potential. The degree of localizationof linear bulk and corner modes emerging due to the rotation increaseswith the increase of rotation frequency. Consequently, corner andbulk solitons in rotating waveguide arrays become thresholdless forsufficiently large rotation frequencies, in contrast to solitons innonrotating arrays that exist only above the power threshold. Focusingnonlinearity enhances the localization degree of corner modes, butsurprisingly initially it leads to broadening of bulk nonlinear states,followed by their relocalization at high input powers. Our resultsopen new prospects for control of evolution of nonlinear multidimensionalexcitations by dynamically varying potentials.