METHOD FOR MEASUREMENT OF REALISTIC 2ND-MOMENT PROPAGATION PARAMETERSFOR NONIDEAL LASER-BEAMS

A method is proposed for the assessment of meaningful second-moment pr opagation parameters for real laser beams aberrated by widely scattere d light in their transverse irradiance profiles. The method relies pri marily on the curves describing the propagation parameters as function s of the fraction of the total beam power enclosed within the limits o f integration of the second-moment integrals. Rapid changes in the pro pagation parameters as the fractional power content approaches unity c learly indicate the presence of widely scattered outer wings or noise in the beams' profiles. The values taken by the propagation parameters in the region where the rapid changes begin to manifest themselves ar e expected to give the realistic propagation parameters for the analys ed laser beam. The method is demonstrated using irradiance profiles me asured from a He-Ne laser beam, and allows for an educated a posterior i assessment of the propagation parameters without using any predeterm ined numerical criteria for the limits of integration of the second-mo ment integrals.