Optical Spin Skyrmions: Topological Light Textures

• Optical spin skyrmions are topological spin textures formed by mapping two-dimensional space onto order-parameter spheres such as the Poincaré sphere.
• They are generated and controlled using structured light, evanescent fields, and integrated photonic systems to create diverse, tunable spin configurations.
• These textures enable precise manipulation in applications ranging from subwavelength metrology and optical communication to magnetic skyrmion memory and data storage.

Optical spin skyrmions are topological spin textures associated either with light itself or with magnetic skyrmions addressed by light. In one usage, two-dimensional real space is mapped onto an optical order-parameter sphere, most commonly the Poincaré sphere of polarization, the sphere of normalized electric-field directions, or the sphere of normalized spin angular momentum density. In another, structured or ultrafast light is used to generate, drive, encode, or read magnetic skyrmions in matter. The common mathematical core is a skyrmion number built from a three-component unit vector field, but the physical field can be optical, magneto-optical, or magnetic depending on context (Tsesses et al., 2018, Cao et al., 17 Feb 2026, He et al., 4 May 2026, Kalin et al., 2023).

1. Topological framework and terminology

The unifying definition is the skyrmion number

$$N = \frac{1}{4\pi}\int \mathbf{n}\cdot\left(\partial_x \mathbf{n}\times \partial_y \mathbf{n}\right)\,dx\,dy,$$

with $\mathbf{n}(x,y)$ a normalized three-component field. What changes across the literature is the identity of $\mathbf{n}$. In evanescent-field optics, $\mathbf{n}$ can be the normalized electric-field direction $\mathbf{e}=\mathbf{E}/|\mathbf{E}|$, yielding an optical skyrmion lattice defined directly by the real-space vector field (Tsesses et al., 2018). In structured-light polarization formulations, $\mathbf{n}$ is instead a normalized Stokes vector on the Poincaré sphere, and the skyrmion number measures the degree of wrapping of polarization space by the transverse beam profile (Cao et al., 17 Feb 2026). In hybrid free-space fields, electric-field, spin, and Stokes skyrmions can coexist in the same diffracted beam, with separate order parameters and separate topological charges for each degree of freedom (Yao et al., 2024).

This multiplicity of definitions is not merely terminological. It marks a genuine stratification of optical topology. A skyrmion may live in the instantaneous electric field, in the time-averaged SAM density, in the Stokes vector of the transverse polarization state, or in a magnetic texture driven by light. A frequent misconception is to treat all optical skyrmions as intensity patterns. The structured-light literature instead places the topology in vectorial degrees of freedom rather than in intensity or phase alone (Cao et al., 17 Feb 2026). Another source of ambiguity is platform dependence: for the specific definition based on a real normalized electric field, evanescence is essential, whereas free-space realizations become natural when the order parameter is taken to be a Stokes or spin field (Tsesses et al., 2018, Shen et al., 2021).

2. Confined-field, evanescent, and polaritonic realizations

A foundational realization of optical skyrmions uses six TM-polarized guided waves arranged as three counter-propagating pairs. Their interference produces a hexagonal lattice in which each unit cell carries skyrmion number $S=1$. In that formulation, the order parameter is the normalized electric-field direction, and the texture can be tuned continuously from bubble-type to Néel-type by varying the confinement parameter $k_\parallel/k_0$. The lattice was experimentally demonstrated with surface plasmon polaritons and phase-resolved near-field optical microscopy, establishing that optical skyrmions can be generated and measured in planar evanescent systems with robust near-integer topology despite loss and finite size (Tsesses et al., 2018).

A complementary route uses the photon spin density itself. In confined electromagnetic fields with orbital angular momentum, the local SAM density

$$\mathbf{S}=\mathrm{Im}\!\left[\varepsilon\,\mathbf{E}^*\times\mathbf{E}+\mu\,\mathbf{H}^*\times\mathbf{H}\right]$$

plays the role of the magnetization vector. For evanescent optical vortices, the resulting SAM texture is Néel-type; for tightly focused vortex beams, the central region becomes Bloch-type-like. The distinctive result is scale separation between intensity and spin structure: while the intensity remains diffraction-limited, the spin direction varies on deep-subwavelength scales down to $1/60$ of the wavelength, about $\mathbf{n}(x,y)$0 nm (Du et al., 2018). This made photonic skyrmions a candidate for subwavelength metrology, chiral nanophotonics, and spin-structured near fields.

An earlier spinor-wave realization appeared in exciton-polariton microcavities. There, the linear optical spin-Hall effect generates alternating circular-polarization domains that form a Skyrmion lattice in the polariton pseudospin field. In the nonlinear regime, spin-anisotropic polariton-polariton interactions compress the spin domains and drive an abrupt transmutation from Skyrmions to half-solitons, accompanied by focalization of spin currents and a strongly anisotropic emission pattern (Flayac et al., 2012). This established that optical spin skyrmions are not restricted to passive structured beams; they also arise as dynamical topological textures in driven-dissipative spinor fluids.

3. Free-space structured-light families

Free-space vector beams made optical spin skyrmions systematically tunable. A major step was the introduction of a generalized two-parameter family $\mathbf{n}(x,y)$1 on the “Skyrme-Poincaré sphere,” which unifies Néel-, Bloch-, and anti-skyrmion textures within a single structured-light framework. In that construction, the skyrmion texture is encoded in the local Stokes vector of a vector beam synthesized from spatial modes in orthogonal circular polarizations, and experimental generation was demonstrated with an SLM-based interferometric system (Shen et al., 2021). The Skyrme-Poincaré sphere made clear that texture type and underlying spin-orbit composition can be varied continuously without leaving the broader topological family.

The same logic was extended to hybrid optical skyrmions involving multiple order parameters in one field. A vector beam truncated by an annular aperture can generate a Néel-type electric-field skyrmion, while a circularly polarized vortex input with $\mathbf{n}(x,y)$2 and $\mathbf{n}(x,y)$3 produces simultaneously an electric-field meron pair, a Bloch-type spin skyrmion, and a second-order Stokes skyrmion. On the plane $\mathbf{n}(x,y)$4, the spin skyrmion carries $\mathbf{n}(x,y)$5 and the Stokes skyrmion $\mathbf{n}(x,y)$6, showing that one structured beam can host distinct topological textures in electric-field, SAM, and Stokes sectors at once (Yao et al., 2024).

Two later directions enlarged the taxonomy. “Fractional optical skyrmions” showed that non-integer orbital angular momentum can generate non-integer skyrmion numbers through partial coverage of the Poincaré sphere and branch-cut discontinuities in the polarization field. The resulting $\mathbf{n}(x,y)$7 varies nonlinearly and exhibits abrupt jumps near half-integers, which the authors interpret as reinforcing the fundamentally integer character of skyrmion topology even in nominally fractional states (Cao et al., 17 Feb 2026). “Tailoring ultra-high-order optical skyrmions” then pushed the order to skyrmion number up to $\mathbf{n}(x,y)$8, demonstrated transitions between skyrmions and bimerons, and used perfect vortex beams to keep transverse size nearly independent of topological order while preserving propagation stability (Zeng et al., 6 May 2025). In parallel, a Manakov-system treatment of two-component spin-$\mathbf{n}(x,y)$9 fields produced localized oscillatory skyrmion-like textures with concentric rings alternating between the two spinor components, and identified the most stable configurations as those with a phase difference of $\mathbf{n}$0 between neighboring rings; the same solutions were stated to be applicable to doubly polarized optical pulses (Javed et al., 2021).

4. Integrated, programmable, and topologically transported platforms

Integrated photonics turned optical spin skyrmions from static beam constructions into programmable states. In valley photonic crystal waveguides, the order parameter is the normalized SAM density

$\mathbf{n}$1

and the skyrmion number is computed over a hexagonal unit cell. A waveguide formed by two valley photonic crystals with valley Chern numbers $\mathbf{n}$2 and $\mathbf{n}$3 supports topological edge states below the light line whose evanescent fields carry Néel-type SAM skyrmions. For one valley-edge eigenstate, the two adjacent unit cells have $\mathbf{n}$4 and $\mathbf{n}$5; switching from the $\mathbf{n}$6 to the $\mathbf{n}$7 valley flips the skyrmion polarity. Because the skyrmions are eigenstates of topological edge transport, their propagation remains robust through Z-shaped bends and two classes of structural defect (He et al., 4 May 2026).

A distinct integrated implementation uses a silicon microring-resonator optical phased array. There, optimized inner- and outer-grating microrings provide decoupled left- and right-circularly polarized radiation bases with polarization fractions of $\mathbf{n}$8 and $\mathbf{n}$9. Independent phase programming of the two spin channels enables switching between Néel-type and Bloch-type optical skyrmions while dynamically tuning the skyrmion number across $\mathbf{n}$0 to $\mathbf{n}$1. The same platform supports a 4-symbol free-space communication link, and under Kolmogorov turbulence the skyrmion-encoded channel maintains a lower symbol error rate over a broader turbulence range than ideal LG-OAM encoding (Cai et al., 11 May 2026). This indicates that integrated optical skyrmions can function not only as field textures but also as programmable information carriers.

5. Light as writer, driver, and encoder of magnetic skyrmions

A second major meaning of optical spin skyrmions concerns magnetic skyrmions manipulated by light. In the multiferroic semiconductor GaV$\mathbf{n}$2S$\mathbf{n}$3, time-resolved magneto-optical Kerr spectroscopy and micromagnetic simulations showed that femtosecond optical excitation can launch coherent modes of a Néel-type skyrmion lattice through a thermal reduction of uniaxial anisotropy. The pump-induced lattice heating was estimated to produce about a $\mathbf{n}$4 decrease of $\mathbf{n}$5, sufficient to excite a skyrmion breathing mode at $\mathbf{n}$6 GHz and a weaker counter-clockwise rotational mode at $\mathbf{n}$7 GHz (Padmanabhan et al., 2018). The mechanism is explicitly thermal-anisotropy-driven rather than inverse-Faraday-driven, and it established optical access to collective skyrmion dynamics in an anisotropic semiconductor host.

In bulk Fe$\mathbf{n}$8Co$\mathbf{n}$9Si, focused femtosecond laser pulses were then used to create and annihilate metastable skyrmion patches by local thermal quenching. Time-resolved MOKE served as a readout by detecting the microwave breathing mode of the metastable skyrmion lattice, and the study identified well-separated magnetic-field regimes together with different fluence thresholds for optical creation and optical annihilation (Kalin et al., 2023). This moved the field from mode excitation to all-optical writing, deleting, and reading of magnetic skyrmions in a model chiral magnet.

At the nanophotonic interface, inverse-Faraday driving in a plasmonic metasurface provides a route to magnetic-field skyrmion crystals. A hexagonal array of gold nanodisks under circularly polarized illumination supports unidirectional drift photocurrents in the disks and counterpropagating “phantom currents” in the interstices, yielding a Néel-type skyrmion-topological lattice of the quasi-static magnetic field above the surface. Under optimal conditions, $\mathbf{e}=\mathbf{E}/|\mathbf{E}|$0 and $\mathbf{e}=\mathbf{E}/|\mathbf{E}|$1, the topological charge per unit cell reaches $\mathbf{e}=\mathbf{E}/|\mathbf{E}|$2, and the skyrmion sign reverses with optical helicity (Yang et al., 31 Mar 2025). A more explicit topological correspondence was formulated on the higher-order Poincaré sphere, where structured light with winding number $\mathbf{e}=\mathbf{E}/|\mathbf{E}|$3 was shown to encode magnetic skyrmions, antiskyrmions, skyrmionium, and skyrmion bags through Zeeman coupling, with total magnetic topological charge constrained by

$\mathbf{e}=\mathbf{E}/|\mathbf{E}|$4

(Qifan et al., 30 Jan 2026). This relation makes the light–magnetism connection explicitly topological rather than merely heuristic.

6. Spectroscopy, applications, and emerging regimes

Optical detection has also entered the quantum-skyrmion regime. A Brillouin-light-scattering protocol was proposed for frustrated magnets in which the relevant quantum degree of freedom is the skyrmion helicity. In the selected geometry, classical skyrmions produce symmetric BLS sidebands, whereas quantum skyrmions produce a distinct Stokes/anti-Stokes asymmetry arising from vacuum fluctuations and unequal occupations of quantized helicity levels. The asymmetry is strongest at low temperature and can be tuned by the input laser power, making sideband asymmetry a direct witness of non-classical skyrmion dynamics (Sharma et al., 20 Jun 2025).

Across the optical and magneto-optical literature, the dominant application themes are communication, metrology, sensing, and information storage. Fractional optical skyrmions introduce continuously tunable topological degrees of freedom for optical communication and sensing (Cao et al., 17 Feb 2026). Ultra-high-order and perfect-vortex skyrmions target topologically resilient communication and memory with much enhanced information capacity (Zeng et al., 6 May 2025). Valley-locked and microring-based implementations address on-chip directional transport, topological routing, and turbulence-tolerant free-space links (He et al., 4 May 2026, Cai et al., 11 May 2026). On the magnetic side, light-driven creation, annihilation, and mode control point toward all-optical skyrmion memories and optically assisted skyrmion devices (Padmanabhan et al., 2018, Kalin et al., 2023).

A persistent conceptual caution is that “optical spin skyrmion” does not denote a single invariant physical object. Depending on the platform, the topological field may be the electric-field direction, the SAM density, the Stokes vector, a pseudospin field, or a magnetic texture addressed by light. What unifies these disparate systems is not material composition or experimental geometry but a common real-space-to-order-parameter mapping, a quantized or near-quantized skyrmion number, and the use of spin–orbit structure to make topology optically accessible.