Simultaneous detection of refractive index and sound velocity in liquid solvents using topological interface states in phoxonic crystal waveguides

Topologically protected boundary states in artificially photonic and phononic materials offer a promising platform for the design of robust wave devices due to their inherent immunity to structural perturbations. In this study, we propose phoxonic crystal (PxC) waveguides for simultaneous guidance of electromagnetic and acoustic waves, and numerically investigate their wave characteristics using finite element analysis. It is demonstrated that both the topologically trivial and non-trivial phases could be realized by varying the PxC waveguides’ geometric parameters, enabling the creation of PxC structures supporting the zero-dimensional topological interface states (TISs) for both electromagnetic and acoustic waves. The developed TISs are subsequently applied for the detection of refractive index and sound velocity of water/1-propanol mixtures with different concentrations. Notably, the sensing performance of the topological PxC waveguides maintain remarkable stability against intentionally introduced structural perturbations.