Deep-subwavelength resolution detection of polar magnetization by optical spin meron lattices on hyperbolic metamaterials

Magnetic-optical Kerr or Faraday effects have been widely used to measure magnetic domain structures by analyzing far-field polarization properties, with resolution limited by the wavelength scale of light. Here, we propose a methodology to measure the magnetic domain at a deep-subwavelength scale by investigating the interactions between a magnetic film and a topological meron spin lattice on the surface of hyperbolic metamaterials (HMMs), which support high-k modes. By introducing a grating structure on the HMM surface to excite volume plasmon polaritons, optical meron spin lattices are formed on the outer surface of the HMM. Subsequently, utilizing the spin–orbit couplings of the topological lattices in the presence of magnetization, a 0.158λ resolution and 100 % high-precision detection of the magnetic domain structures with random polar orientations was achieved by altering the incident polarizations from right-handed to left-handed circular polarizations and summing the out-of-plane spin distributions. The findings offer opportunities for the visualization of magnetic domain structure with polar orientation of magnetization and in turn for the development of novel photonic spin topologies using complex magnetization patterns.