Optical second-order skyrmionic hopfion

Due to their topological stability and spatial confinement, particle-like field configurations have gained significant interest in many areas of physics. Only recently, the first skyrmionic hopfion was proposed in light, but its higher-order analog in optics has stayed a theoretical construct so far, and direct experimental observations also prove difficult in non-optical systems. Here we overcome this challenge by the experimental realization and analysis of a second-order skyrmionic hopfion in the polarization and phase texture of a paraxial light field in three-dimensional space. Thereby, we exemplify advanced control of observed parameters in a localized space, pioneering further experimental studies on higher-order hopfions in optics and beyond. Published by Optica Publishing Group under the terms of the Creative Commons Attribution 4.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.