Near field optics
Near Field Optics is a method used in nanotechnology to study localized light-matter interactions and to visualize fields confined to a surface, such as waveguide modes, surfaces polaritons and electromagnetic waves that propagate at the interface between two media.
In contrast with ordinary optics, where an object is normally irradiated by a light source and the scattered or emitted light is recorded by a detector, in near field optics, an object is split into two parts; the probe and the sample. The probe is normally engineerd to exploit the unique properties of metal nanostructures at optical frequencies to localize incident radiation and enhace the light-matter interaction with the sample.
This technique assisted the development of nanoplasmonics and single-molecule spectroscopy among others.