Acoustic chiral mode switching by dynamic encircling of exceptional points

Chiral mode switching initiated by dynamic encircling of an exceptional point (EP) has shown an extraordinary ability in wave controlling. In this work, we study the chiral mode transfer for acoustic waves in the coupled waveguide system that supports the non-adiabatic evolution of eigenstates. The system comprises a finite number of structural elements, which are constructed according to parametric conditions in the loop enclosing the EP and then stacked such that acoustic propagation in the waveguide system is equivalent to the dynamic encircling of the EP. An analytic model based on the spatial coupled-mode theory is developed, which provides a practical guide to design the system and makes predictions for dynamic evolution. Numerical simulation of the waveguide system is conducted to demonstrate the chiral mode switching for sounds.