The Goos–Hänchen effect is an optical phenomenon

Optical phenomenon

An optical phenomenon is any observable event that results from the interaction of light and matter. See also list of optical topics and optics. A mirage is an example of an optical phenomenon....

 in which linearly polarized

Linear polarization

In electrodynamics, linear polarization or plane polarization of electromagnetic radiation is a confinement of the electric field vector or magnetic field vector to a given plane along the direction of propagation...

 light undergoes a small shift, when totally internally reflected

Total internal reflection

Total internal reflection is an optical phenomenon that happens when a ray of light strikes a medium boundary at an angle larger than a particular critical angle with respect to the normal to the surface. If the refractive index is lower on the other side of the boundary and the incident angle is...

. The shift is perpendicular to the direction of propagation, in the plane containing the incident and reflected beams. This effect is the linear polarization analog of the Imbert–Fedorov effect.

This effect occurs because the reflections of a finite sized beam will interfere along a line transverse to the average propagation direction. As shown in the figure, the superposition of two plane waves with slightly different angles of incidence but with the same frequency or wavelength is given by



where



and



with .

It can be shown that the two waves generate an interference pattern transverse to the average propagation direction, and on the interface along the plane.

Both waves are reflected from the surface and undergo phase shifts.

This effect continues to be a topic of scientific research, for example in the context of nanophotonics applications. The work by Merano et al. studied the Goos–Hänchen effect experimentally for the case of an optical beam reflecting from a metal surface (gold) at 826 nm. They report a substantial, negative lateral shift of the reflected beam in the plane of incidence for a p-polarization and a smaller, positive shift for the s-polarization case.