Mapping the near-field distribution of magnetic fields using a silicon nanoparticle at optical frequencies

Mapping the near-field distribution of vector-field components, including those of the electric and magnetic fields, is crucial for understanding the intricate physical processes in the near field. However, imaging the near field of magnetic fields is challenging. We propose a flexible technique for mapping the longitudinal magnetic field using a nano-antenna probe. Unlike traditional techniques for mapping the near field of the magnetic field with a symmetry breaking probe, the magnetic resonances of silicon nanoparticles are analyzed and the directionally scattered light is extracted to reconstruct the longitudinal magnetic field distribution. An artificial mapping system is set up to verify whether the longitudinal magnetic component can be mapped. Using this technique, the conversion of spin angular momentum to orbital angular momentum is also demonstrated. The potential application of this technique is the full vector-field mapping of the electromagnetic fields and the near-field visualization of physical processes.