Observation of nonlinearity-controlled switching of topological edge states

TL;DR

This paper experimentally demonstrates how topological edge states in waveguide arrays can be switched periodically through their modal overlap, with the switching rate controllable by array spacing and input power.

Contribution

It presents the first experimental observation of power-controlled, nonlinearity-driven switching of topological edge states in laser-written waveguide arrays.

Findings

Switching occurs due to modal overlap of edge states from topological forbidden gap.

Switching rate increases as array spacing decreases.

Switching can be controlled or halted by adjusting input power.

Abstract

We report the experimental observation of the periodic switching of topological edge states between two dimerized fs-laser written waveguide arrays. Switching occurs due to the overlap of the modal fields of the edge states from topological forbidden gap, when they are simultaneously present in two arrays brought into close proximity. We found that the phenomenon occurs for both strongly and weakly localized edge states and that switching rate increases with decreasing spacing between the topological arrays. When topological arrays are brought in contact with nontopological ones, switching in topological gap does not occur, while one observes either the formation of nearly stationary topological interface mode or strongly asymmetric diffraction into the nontopological array depending on the position of the initial excitation. Switching between topological arrays can be controlled and even completely arrested by increasing the peak power of the input signal, as we observed with different array spacings.