Sub-wavelength acoustical vortex beams using self-demodulation

Abstract

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

@article{Jimenez2021subvortex,
 author = {Noé Jiménez and Joao Ealo and Rubén D. Muelas-Hurtado and Aroune Duclos and Vicent Romero-García},
 doi = {https://doi.org/10.1103/PhysRevApplied.15.054027},
 issn = {N/D},
 journal = {Physical Review Applied},
 month = {05},
 number = {5},
 pages = {054027},
 title = {Sub-wavelength acoustical vortex beams using self-demodulation},
 url = {https://journals.aps.org/prapplied/abstract/10.1103/PhysRevApplied.15.054027},
 volume = {15},
 year = {2021}
}