Bound states with orbital angular momentum in the continuum of cylindrical non-axisymmetric waveguide

Lyapina, A. A.; Pilipchuk, A. S.; Sadreev, A. F. Source: ANNALS OF PHYSICS, 396 56-70; 10.1016/j.aop.2018.05.020 SEP 2018

We consider acoustic wave transmission in a non-axisymmetric waveguide which consists of a cylindrical resonator of radius and length and two cylindrical waveguides of radius whose axes are shifted relative to the axis of the resonator and relative to each other by azimuthal angle . We find multiple bound states in the continuum (trapped modes) with nonzero orbital angular momentum under variation of due to full destructive interference of resonant modes leaking into waveguides. For we find the degenerate bound states in the continuum whose contribution into the scattering wave function is complex and supports giant vortical acoustic intensity spinning inside the resonator.