Optical skyrmions are quasiparticles with nontrivial topological textures that have significant potential in optical information processing, transmission, and storage. Here, we theoretically and experimentally achieve the conversion of optical skyrmions among Néel, Bloch, intermediate skyrmions, and bimerons by polarization devices, where the fusion and annihilation of optical skyrmions are demonstrated accordingly. By analyzing the polarization pattern in Poincaré beams, we reveal the skyrmion topology dependence on the device, which provides a pathway for the study of skyrmion interactions. A vectorial optical field generator is implemented to realize the conversion and superposition experimentally, and the results are in good agreement with the theoretical predictions. These results enhance our comprehension of optical topological quasiparticles, which could have a significant impact on the transfer, storage, and communication of optical information.

We report the method of producing a spatio-temporal (ST) wave packet carrying pure transverse orbital angular momentum (OAM) with subwavelength spatial sizes. Due to the lack of temporal focusing, an ST wave packet focused by a high numerical aperture (NA) objective lens experiences a “spatio-temporal astigmatism” effect similar to the focusing action of a cylindrical lens on the transverse profile of optical field. Thus an ST vortex with a spiral phase in the ST domain focused through a high NA objective will be distorted and lose the ST characteristic spiral phase pattern. With the understanding of such an ST astigmatism, the ST wave packet can be pre-conditioned such that an ST vortex carrying OAM with subwavelength transverse sizes can be obtained after strong focusing. This is the first revelation that a tightly focused ST vortex beam with transverse OAM can be realized, paving the way for potential applications including microscopy, optical trapping, laser machining, nonlinear light-matter interactions, and so on. The ST astigmatism effect also offers insights for the focusing and propagation studies of other types of ST wave packets.

We experimentally generate cylindrically polarized wavepackets with transverse orbital angular momentum, demonstrating the coexistence of spatiotemporal optical vortex with spatial polarization singularity. The results in this paper extend the study of spatiotemporal wavepackets to a broader scope, paving the way for its applications in various areas such as light–matter interaction, optical tweezers, spatiotemporal spin–orbit angular momentum coupling, etc.

Optical skyrmions, which are topological quasi‐particles with nontrivial electromagnetic textures, have garnered escalating research interest recently for their potential in diverse applications. In this paper, we present a method for generating tightly focused optical skyrmion and meron topologies formed by electric‐field vectors under 4 π ‐focusing system, where both the topology types (including Néel‐, Bloch‐, intermediate‐ and anti‐skyrmion/meron) and the normal direction of the two‐dimensional topology projection plane can be tailored at will. By utilizing time‐reversal techniques, we analytically derive the radiation pattern of a multiple concentric‐ring array of dipoles (MCAD) to obtain the required illumination fields on the pupil planes of the two high numerical aperture lenses. The Deby vector diffraction integral theory is employed to calculate the corresponding tightly focused field, and their topology characteristics are quantitatively evaluated by the electric‐field vector distribution. The results demonstrate that arbitrary electric‐field based skyrmion and meron can be conveniently generated by adjusting the oscillation direction of each dipole in the MCAD and the normal direction of the dipole array. The generated optical topologies with fully controllable degrees of freedom provide potential applications in optical information processing, transmission, and storage.

Pulse shaping has become a powerful tool in generating complicated ultrafast optical waveforms to meet specific application needs. Traditionally, pulse shaping focuses on the temporal waveform synthesis. Recent interests in structuring light in the spatiotemporal domain rely on Fourier analysis. A space-to-time mapping technique allows us to directly imprint complex spatiotemporal modulation through taking advantage of the relationship between frequency and time of chirped pulses. The concept is experimentally verified through the generation of spatiotemporal optical vortex (STOV) and STOV lattice. The power of this method is further demonstrated by STOV polarity reversal, vortex collision, and vortex annihilation. Such a direct mapping technique opens tremendous potential opportunities for sculpturing complex spatiotemporal waveforms.