Thick lens model for self-focusing in Kerr medium

Abstract

An asymmetric “thick-lens” model for self-focusing in Kerr medium of finite thickness is presented by introducing a complex curvature radius of a Gaussian beam in nonlinear medium and a transfer matrix for the transition from linear to nonlinear medium. With this model the linear ABCD-matrix formalism can be extended to nonlinear optical systems with a clear physical insight. The modulation of the cavity transverse mode of a resonator containing a Kerr medium is characterized by the asymmetry of the “thick lens.” The intracavity small-signal relative spot size variation outside as well as inside the Kerr medium can be calculated efficiently with the “thick-lens”-like matrix formalisms. Criteria for the design and optimization of a Kerr-lens mode-locked laser resonator with a hard or soft aperture are predicted.