Topology Optimization of Chiral Phoxonic Crystals with Simultaneously Large Phononic and Photonic Bandgaps

We study theoretically the simultaneous existence of large phononic and photonic bandgaps in chiral phoxonic crystals by topology optimization. By analyzing the effect of the chiral symmetry with different material orientations in both the square and triangular lattices, we discuss the most suitable structural properties for opening large phononic and photonic bandgap widths simultaneously and demonstrate the key role of the chiral topological feature. We also present the sensitivity analysis on the optimized phoxonic crystals and suggest the relatively robust structures. It will be shown that topology optimization can discover novel types of simple structures, offering new degrees of freedom to the beneficial design of phoxonic crystals for manipulating photons with phonons.