title: Concept of purity in the theory of optical polarization.
abstract: It was shown some time ago that the space-time and the space-frequency degrees of polarization of a stochastic electromagnetic beam are not equivalent to each other. It is not possible, in general, to obtain a formal relationship between them. In this Letter, we discuss certain conditions under which they are directly related. These conditions lead to the concept of polarization-purity. If an optical beam obeys these conditions, its space-frequency degree of polarization has the same value at all frequencies present in the spectrum, and the value is equal to the space-time degree of polarization.
authors.affiliation: Department of Physics and Astronomy, University of Rochester, Rochester, New York 14627, USA. mayukh@pas.rochester.edu
authors.forename: Mayukh
authors.initials: M
authors.lastname: Lahiri