Optical fibres can now directly generate a variety of Bessel beams thanks to custom-designed, intricate 3D-printed structures applied to their tips. Structured light refers to light beams that look very different from the usual visual picture that one holds of a conventional laser beam of a narrow spot with a smooth, continuous Gaussian-shaped transverse intensity profile. For example, take the family of Bessel beams. These beams are eigen solutions of the Helmoltz equations without any paraxial approximation that typically feature oscillatory intensity patterns resembling a bullseye. As higher order solutions of propagating light fields in free space, bulk media and optical fibres, Bessel beams possess intriguing properties not typically found in conventional Gaussian beams.

Link: https://doi.org/10.1038/s41566-022-01070-3