Experimental observation of edge states in SSH-Stub photonic lattices

We reveal unconventional edge states in a one-dimensional Stub lattice of coupled waveguides with staggered hoppings. The edge states appear for the same values of hoppings as topological edge states in the Su-Schrieffer-Heeger model. They have different energies depending on the lattice termination and present a remarkable robustness against certain types of disorder. We evidence experimentally the phase transition at which these edge states appear, opening the door to the engineering of one-dimensional lattices with localized edge modes whose energy and location can be controlled at will.