Subwavelength Acoustic Vortex Beams Using Self-Demodulation

Acoustic vortices with subwavelength dimensions and tunable topological charge are theoretically experimentally synthesized at distances far beyond the Rayleigh diffraction length of source, using self-demodulation. A dual helical acoustic source is used to generate two primary confocal vortex beams different frequencies charges. As a consequence conservation angular momentum during nonlinear wave mixing, self-demodulated beam difference frequency emerges, keeping spatial features that their We report subdiffractive characteristic size which 18 times smaller than its wavelength distance 2.8 length. The generation focusing paves way for long-range communication, biomedical, wave-matter interaction applications.