Satellite rings in solid state lasers

The intensity distribution of the nonlocalized rings from a Fabry-Perot standard is calculated. This is illuminated by a point source in order to characterize the interference pattern. The results show that the rings are identical with the nonlocalized rings around the principal (Gaussian) beam from a solid state laser (ruby or neodymium). A synthesis of the results obtained by different authors is presented, and we show that the rings arise from energy losses caused by diffusion or reflection of the Gaussian beam in the laser cavity.