Direct measurement of the real strength of near-field electric field

Measurement of the real strength value of near-field electric fields is of great importance for understanding light–matter interactions in nanophotonics, which is a big challenge in the field. We developed in this study a theory and approaches for directly measuring the real strength of near-field electric fields by scattering type scanning near-field optical microscope (s-SNOM). The validity of the theory and approaches was confirmed by comparing s-SNOM measurement results with the finite element method simulations. Our efforts enable s-SNOM as a quantitative tool in clarifying light–matter interactions in a variety of fields, such as all-optical chips, plasmon-induced catalysis, metamaterials and metasurfaces, enhanced spectroscopy, and van der Waals materials, etc.