Abstract
In this work we show that scattered acoustic vortices by broadband metasurfaces with chiral symmetry present unusual far-field properties. To test this concept a broadband spiral metasurface was designed based on holographic vortices. In the near field phase dislocations with tuned topological charge emerge as the destructive interference of the scattered waves at the axis of the spiral metasurface. In the far field, metasurfaces based on holographic vortices inhibit specular reflections because all scattered waves also interfere destructively at the specular direction. In addition, as reflected waves diverge spherically from the holographic focal point, the scattering function in the far field is unusually uniform. In particular, the proposed metasurface design present a mean correlation-scattering coefficient of 0.99 (0.98 in experiments) and a mean normalized diffusion coefficient of a 0.73 (0.76 in experiments) in a frequency band covering 4 octaves. These two exceptional features make spiral metasurfaces exceptional candidates to control acoustic scattering and generate diffuse sound reflections in underwater acoustics, room acoustics or biomedical ultrasound beamforming applications.
BibTeX citation
@article{Jimenez2021vortexdiff,
author = {Noé Jiménez and Jean-Philippe Groby and Vicent Romero-García},
doi = {https://doi.org/10.1038/s41598-021-89487-8},
issn = {N/D},
journal = {Scientific Reports},
month = {05},
pages = {10217},
title = {Spiral sound-diffusing metasurfaces based on holographic vortices},
url = {https://www.nature.com/articles/s41598-021-89487-8},
volume = {11},
year = {2021}
}