image: Figure | Conceptual schematic of white light skyrmions generation from a single dome-shaped ferroelectric spherulite. a, Generation schematics of white light skyrmions from one single ferroelectric spherulite. The dome-shaped spherulite was consisted of azimuthally oriented rodlike polar molecules of the uniaxial anisotropy, showing the rotation symmetry in both geometry and optical properties. The input beam of right circular polarization experienced spin-orbital coupling and was subsequently focused by the dome-shaped ferroelectric spherulite to form Stokes skyrmionic topologies in the far field. In the case of white light incidence, skyrmionic topologies were formed at each wavelength, taking red skyrmions, green skyrmions, and blue skyrmions as examples. Inset: scanning electron microscope image of the fabricated spherulite. The scalebar of the scanning electron microscope image is 5 mm. b, Texture and synthesis of white light optical skyrmions. The left circular polarization with LG0,-2 mode and right circular polarization with LG0,0 mode were robustly formed in the far field due to the spin-orbital coupling effects in the case of right circular polarization incidence. Mapping such Stokes distribution to a Poincaré sphere, it exhibits the topological feature of a quasi-particle. Bottom panel in (b): the colour (lightness) represents the phase (intensity) of the complex fields of the left circular polarization and right circular polarization. In (a) and the top panel of (b), the hue of the vector arrows represents different in-plane components of the Stokes vectors, and the lightness of the vector arrows corresponds to out-of-plane components of the Stokes vectors. Amp., amplitude.
Credit: Jingbo Sun et al.
Optical skyrmions, as topologically protected light fields, are emerging as powerful candidates for next-generation information carriers due to their stability against defects and noise. However, the realization of optical skyrmions has long been confined to single-color or narrow-band regimes. This fundamental bottleneck arises because current mainstream technologies, such as metasurfaces and microcavities, rely heavily on resonant effects, which intrinsically suffer from strong spectral dispersion. Consequently, achieving broadband, full-color skyrmion generation on a chip remains a critical challenge for advancing high-dimensional optical technologies.
In a new paper published in eLight, a team of scientists, led by Professor Jingbo Sun and Professor Ji Zhou (Tsinghua University, China), and Professor Yijie Shen (Nanyang Technological University, Singapore), have developed a revolutionary solution. They proposed and experimentally demonstrated a broadband skyrmion generator based on on-chip ferroelectric spherulites. Unlike traditional top-down nanofabrication, these spherulites are dome-shaped microstructures formed through self-assembly with inherent circular birefringence. By leveraging the spin-orbit coupling of light within these structures, the team successfully generated optical skyrmions spanning the entire visible band from 450 nanometers to 785 nanometers. More importantly, the generated skyrmions exhibit excellent topological stability over a propagation distance of seven Rayleigh lengths.
"The key advantage of our platform is that it completely avoids the resonance constraints of artificial nanostructures. The ferroelectric spherulite acts as a non-resonant optical element. When circularly polarized light illuminates the dome-shaped spherulite, the edge region focuses the beam while the center imparts orbital angular momentum, merging to form a skyrmion texture. This mechanism is inherently wavelength-insensitive, allowing us to achieve 'white-light skyrmions'." they explain.
“Furthermore, the work demonstrated dynamic control over the topological textures. By simply adjusting the polarization state of the incident light, we could switch between different topological quasiparticles, including skyrmions, biskyrmions, and quadrumerons. We also observed spontaneous parametric down-conversion within the ferroelectric material, indicating the potential for generating entangled photonic pairs with topological characteristics.” they added.
“This breakthrough provides a new paradigm for integrating high-capacity wavelength-division multiplexing with topological protection, opening new avenues for future classical and quantum communication technologies.” the scientists forecast.
Journal
eLight
Article Title
Broadband coloured skyrmions generated by on-chip ferroelectric spherulites