Fig. 1: Synthesizing three-dimensional (3D) spatiotemporal (ST) acoustic vortices with orbital angular momentum (OAM) oriented in arbitrary directions.
From: Generation of spatiotemporal acoustic vortices with arbitrarily oriented orbital angular momentum
a Direct rotation of ST acoustic vortices in 3D space. A ST wave packet carrying longitudinal OAM is rotated around the \(x\)-axis, and the direction of OAM will change accordingly, which is indicated by the red arrow in the coordinate system. b Intersection of ST vortices carrying transverse and longitudinal OAM yields a ST wave packet carrying tilted OAM. c Schematic of experimental setup. Spatiotemporal vortices are generated by an acoustic phased array controlled by the sound cards. On the scanning plane at a distance of \({z}_{0}=20\,{cm}\) from the acoustic phased array, we measure the time-domain acoustic pressure signals using a microphone array. A trigger signal is generated simultaneously with the wave packet signal by the sound card and transmitted to the data acquisition module to initiate data collection, ensuring that each captured time-domain acoustic pressure signal is located within the same time interval. d The acoustic phased array consists of 121 loudspeakers with a diameter of D = 4.3 cm, arranged in a two-dimensional rectangular grid with a spacing of L = 5.5 cm. e Photograph of the experimental setup.
