Uploaded June 2025 | Updated September 2026, 1 week ago
Supplementary Video 1: Evolution of intensity and phase profiles of vortex beams with linearly growing orbital angular momentum along the optical path, exhibiting spatial self-torque.
Supplementary Video 2: Evolution of vortex beams whose orbital angular momentum experiences linear growth then decay along the optical path.
Supplementary Video 3: Evolution of vortex beams whose orbital angular momentum decays then grows following a linear dependence along the optical path.
Supplementary Video 4: Evolution of vortex beams whose orbital angular momentum experiences quadratic chirp along the optical path, exhibiting optical rotatum.
Abstract
Vortices are ubiquitous in nature and can be observed in fluids, condensed matter, and even in the formation of galaxies. Light, too, can evolve like a vortex. Optical vortex beams are exploited in light-matter interaction, free space communications, and imaging. Here, we introduce optical rotatum, a behavior of light in which an optical vortex beam experiences a quadratic chirp in its orbital angular momentum along the optical path. We show that such an adiabatic deformation of topology is associated with the accumulation of a Gouy phase factor, which, in turn, perturbs the propagation constant (spatial frequency) of the beam. The spatial structure of optical rotatum follows a logarithmic spiral—a signature that is commonly seen in the pattern formation of seashells and galaxies. Our work expands the previous literature on structured light, offers new modalities for light-matter interaction, communications, and sensing, and hints at analogous effects in condensed matter physics and Bose-Einstein condensates.
Ahmed H. Dorrah, Alfonso Palmieri, Lisa Li, and Federico Capasso. Science Advances. 11 Apr 2025, Vol 11, Issue 15.
DOI: 10.1126/sciadv.adr9092
Supplementary Video 1: Evolution of intensity and phase profiles of vortex beams with linearly growing orbital angular momentum along the optical path, exhibiting spatial self-torque.
Supplementary Video 2: Evolution of vortex beams whose orbital angular momentum experiences linear growth then decay along the optical path.
Supplementary Video 3: Evolution of vortex beams whose orbital angular momentum decays then grows following a linear dependence along the optical path.
Supplementary Video 4: Evolution of vortex beams whose orbital angular momentum experiences quadratic chirp along the optical path, exhibiting optical rotatum.
Abstract
Vortices are ubiquitous in nature and can be observed in fluids, condensed matter, and even in the formation of galaxies. Light, too, can evolve like a vortex. Optical vortex beams are exploited in light-matter interaction, free space communications, and imaging. Here, we introduce optical rotatum, a behavior of light in which an optical vortex beam experiences a quadratic chirp in its orbital angular momentum along the optical path. We show that such an adiabatic deformation of topology is associated with the accumulation of a Gouy phase factor, which, in turn, perturbs the propagation constant (spatial frequency) of the beam. The spatial structure of optical rotatum follows a logarithmic spiral—a signature that is commonly seen in the pattern formation of seashells and galaxies. Our work expands the previous literature on structured light, offers new modalities for light-matter interaction, communications, and sensing, and hints at analogous effects in condensed matter physics and Bose-Einstein condensates.
Ahmed H. Dorrah, Alfonso Palmieri, Lisa Li, and Federico Capasso. Science Advances. 11 Apr 2025, Vol 11, Issue 15.
DOI: 10.1126/sciadv.adr9092
