Acoustics of a finite-aperture Laguerre-Gaussian vortex beam

Abstract

Based on the Rayleigh-Sommerfeld surface integral and the addition theorem for the spherical wave functions, a partial wave series expansion (PWSE) is derived for the incident field of an acoustical spiraling Laguerre-Gaussian vortex beam (LGVB). The description of the incident field in a PWSE in spherical coordinates allows efficient evaluation of the acoustic radiation force and torque on a sphere using the appropriate beam-shape coefficients. The finite vortex beam solution satisfies the Helmholtz equation, and can be used to advantage in beam-forming design and numerical prediction of the mechanical effects of sound LGVBs for applications in particle manipulation and the interaction of acoustic vortex beams with a particle.