High-order mode interface states of surface water waves based on non-Bragg resonances

In this paper, we connect two periodic channels with bandgaps of different physical properties to form a heterojunction of surface water waves, which realize a high-order mode water wave interface state and concentrate the water wave energy near the heterojunction interface. By introducing a spatial symmetry breaking mechanism, we obtain a periodic channel with non-Bragg bandgaps due to different mode resonances. At a similar central frequency of the gap, another periodic channel is designed to generate Bragg bandgaps of the same mode resonances. The results of the mode analysis indicate that the localized region of the interface state in the frequency range of the non-Bragg bandgap contains a high-order mode component, which is dominant. The interface states induced by the high-order modes are much more efficient in wave accumulation. By introducing defect structures with different lengths, the frequency tuning of the high-order mode interface states is also achieved. The high-order mode interface state provides a different way for wave aggregation, and its implementation is also applicable to other classical wave systems due to the ubiquity of wave phenomena.