Fig. 4: Coupling of topological and nontopological edge states.

Experimentally observed light evolution along the propagation direction when the waveguides supporting (a) the topological and (b) the nontopological edge states of the coupled structure, schematically displayed above, are excited. Power oscillations when the waveguide supporting (c) the topological (green line) and (d) the nontopological (blue line) edge state is excited. The y axis is the normalized power extratced from the fluorescence images in a and b. The x axis is the propagation distance in cm. The solid lines correspond to the experimental results while the dashed lines correspond to the tight-binding numerical simulations. The total length of the sample is L = 10 cm, the wavelength used to excite the waveguides is λ = 633 nm and the lattice is composed of N = 99 waveguides.