Probing the Magnetic Field of Light at Optical Frequencies

TLDR

Light is an electromagnetic wave with interdependent electric and magnetic fields, yet at optical frequencies the magnetic component is usually negligible and undetectable by conventional means. Using metamaterial concepts, the authors designed an engineered near‑field aperture probe to interrogate light’s magnetic field. The probe enabled sub‑wavelength visualization of both magnetic and electric field distributions of propagating light.

Abstract

Light is an electromagnetic wave composed of oscillating electric and magnetic fields, the one never occurring without the other. In light-matter interactions at optical frequencies, the magnetic component of light generally plays a negligible role. When we "see" or detect light, only its electric field is perceived; we are practically blind to its magnetic component. We used concepts from the field of metamaterials to probe the magnetic field of light with an engineered near-field aperture probe. We visualized with subwavelength resolution the magnetic- and electric-field distribution of propagating light.