Fluctuations of laser beam parameters

Fluctuations of the first and second generalized beam moments of beams fluctuating randomly or quasiperiodically in time are described. Hence an approach is developed which allows on the on hand to derive the ABCD-transformation of the variances of the moments fluctuations. On the other handit ensures the measurability of these quantities. Characteristic pointing stability and radius stability figures which are invariant in ideal optical systems are derived. The design of an optical system which minimizes beam fluctuations is discussed as an example which is important in materials processing applications.