Simultaneous all-angle self-collimation for both light and sound in phoxonic crystals

We report the all -angle dual optical and acoustic waveguides in defect-free phoxonic crystals. The realization of this function relies on dual flat open equal-frequency contours (EFCs) enabling all -angle self-collimation for both optical and acoustic waves. For incident angles within 85, both light and sound can propagate simultaneously along the propagation direction without diffraction in the proposed defect-free structure. As a potential application of our work, a compact 3 dB phoxonic Y-shaped beam splitter is designed and numerically demonstrated. The coexistence of all -angle optical and acoustic self-collimation allows a new potential possibility to realize integrated management of photons and phonons with an ultracompact footprint size.