title: Strehl ratio of a Gaussian beam.
abstract: We discuss the Strehl ratio of systems with a Gaussian pupil and determine the range of validity of its approximate expression based on the aberration variance. The results given are equally applicable to propagation of Gaussian beams. The uniform and weakly truncated pupils are considered as limiting cases of a Gaussian pupil. We show that the approximate expression for Strehl ratio in terms of the aberration variance yields a good estimate of the true value for a strongly truncated pupil but a much smaller value for a weakly truncated pupil.
authors.affiliation: The Aerospace Corporation, 2350 East El Sugundo Boulevard, El Segundo, California 90245, USA. virendra.n.mahajan@aero.org
authors.forename: Virendra N
authors.initials: VN
authors.lastname: Mahajan