Skyrmion Light

Siméon Denis Poisson predicted — and François Arago confirmed — that coherent light diffracting around an opaque circular disc produces a bright spot at the very center of the geometric shadow. The spot exists because waves traveling around every edge of the disc arrive in phase at the center axis. 208 years later, NTU Singapore found it also encodes topological polarization structure.

Skyrmions were first proposed by nuclear physicist Tony Skyrme (1961) as topologically stable solitons in field theories. In optics, a skyrmion is a configuration of polarization vectors that maps every point on the spatial plane to the Bloch sphere exactly once — a topological charge Q = ±1 that cannot be unwound by any smooth deformation of the field.

Néel skyrmions have polarization vectors pointing radially — like a hedgehog. Bloch skyrmions have vectors twisted 90°, creating a swirl. Both carry the same |Q| = 1 charge but couple to matter differently. NTU's disc method can generate either by controlling the input polarization state of the incident laser beam.

Optical skyrmions are topologically protected — small perturbations cannot destroy them. Until 2026 creating them required expensive spatial light modulators or engineered metamaterials. NTU's discovery that a simple metal disc suffices — no active optics — could democratize skyrmion-based optical trapping, nano-scale imaging, and photonic quantum logic.