In physics, the
Mach–Zehnder interferometer is a device used to determine the relative
phase shift variations between two
collimated beams derived by splitting light from a single source. The
interferometer has been used, among other things, to measure phase shifts between the two beams caused by a sample or a change in length of one of the paths. The apparatus is named after the physicists Ludwig Mach (the son of
Ernst Mach) and
Ludwig Zehnder: Zehnder's proposal in an 1891 article was refined by Mach in an 1892 article.