Fine structure in the reflection of cylindrical light beams

For its everyday familiarity the reflection of light is a surprisingly complicated phenomenon. Although plane waves on reflection from a planar interface simply acquire a complex factor given by the Fresnel coefficients, a confined beam of light, consisting of a spectrum of plane waves, can be shifted in position and angle with respect to the predictions of geometrical optics. One of the most striking examples of these effects is the Goos-Hänchen shift, which is a displacement of the reflected beam within the plane of incidence. The magnitude of this shift is of the order of the wavelength, and is thus small compared to most other length scales in conventional optics, but for the strong light confinement of light-mater interactions at the nanoscale such small displacement effects can become comparable in magnitude to the spatial structures of the interface.