  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.
