Mode-crossing interpretation of resonances in the transverse excess noise factor

Abstract

It is well known that the excess noise factor K of an unstable-cavity laser shows very pronounced peaks at values of the equivalent Fresnel number for which the losses of the two lowest-loss modes become equal. This makes it natural to explore the validity of a two-mode description of K. We report that these resonances of K, as far as their shape and position is concerned, are indeed revealed by a two-mode formalism. The magnitude of the resonances, however, cannot be explained within a two-mode context.