Coherence growth of laser radiation in Gaussian cavities

The beam quality and coherence growth of the laser radiation in stable and unstable cavities equipped with a Gaussian reflectivity mirror as output coupler has been investigated. An experimental analysis of the time evolution of the near- and far-field beam quality factor and spot size in dependence on the cavity configuration has been carried out. A theoretical analysis of the time evolution of a Schell-Gauss model beam propagating through Gaussian cavities is seen to provide a satisfactory description of the process in agreement with the experimental measurements for all the tested resonators.