Analysis of unidirectional operation of Kerr lens mode-locked ring oscillators

The starting of Kerr lens mode-locking operation can be successfully understood by a simple ABCD resonator analysis, which discards the diffractive effects introduced by the hard aperture of the laser cavity. These effects are nevertheless important since they change the intracavity beam shape and need to be considered to explain the observed unidirectional operation in ring resonator configurations. We present a model analysis which, using a Gaussian apodizing aperture, rigorously includes the diffraction of the circulating cavity eigenmode by the aperture.