title: Coherence current, coherence vortex, and the conservation law of coherence.
abstract: Introducing scalar and vector densities for a mutual coherence function, we present a new conservation law for optical coherence of scalar wave fields in the form of a continuity equation. This coherence conservation law provides new insights into topological phenomena for the complex coherence function. Some properties related to the newly introduced coherence vector density, such as a circulating coherence current associated with a coherence vortex, are investigated both theoretically and experimentally for the first time.
authors.affiliation: Department of Information and Communication Engineering, Laboratory for Information Photonics and Wave Signal Processing, The University of Electro-Communications, 1-5-1, Chofugaoka, Chofu, Tokyo 182-8585, Japan. weiwang@ice.uec.ac.jp
authors.forename: Wei
authors.initials: W
authors.lastname: Wang
authors.forename: Mitsuo
authors.initials: M
authors.lastname: Takeda