Generation of Multi-Order Sound Vortices via a Single Non-Hermitian Ring Cavity

Abstract The integration of acoustic vortices with chiral exceptional points (CEPs) in ring cavities enables the controlled unidirectional coupling and manipulation of orbital angular momentum (OAM) modes. However, realizing multiple vortex orders within a single cavity remains challenging because non-Hermitian modulations must be tailored for different OAM modes simultaneously. We propose a simple approach for constructing multiple CEPs by arranging resistive and reactive impedance-boundary modulations with specific azimuthal patterns along the inner wall of an acoustic ring cavity. This design allows for independent engineering of multiple OAM eigenmodes and their simultaneous excitation using a single monopole source. As a representative example, we demonstrate first-, second-, and third-order OAM generation in both an exact P T -symmetric cavity with balanced gain and loss and a loss-biased passive counterpart that offers additional chirality control through the chirality-reversal effect. This study provides a flexible and compact framework for generating and manipulating multi-order acoustic OAM modes on non-Hermitian platforms.