Interferometric determination of a static optical path difference using a frequency swept laser diode

Abstract

Two beams from a coherent light source are recombined to interfere after travelling their respective constant optical paths. The number of intensity changes of the interference fringe observed when the frequency of the source is swept gives information about their unknown static path difference. It is compared with another count which is obtained simultaneously from the intensity changes of another interference fringe made by a reference optical system with a known path difference using part of the light from the same source. The unknown static path difference is given by the ratio of the two counts of the intensity changes. The principle and results of basic experiments performed on the basis of this method are described.