Self-consistent spatial mode analysis of self-adaptive laser oscillators

A theoretical analysis involving ABCD ray transfer matrices is used to find the self-consistent fundamental spatial mode solutions of self-adaptive laser resonators. The resonators investigated consist of a nonlinear medium in a self-intersecting loop geometry together with a feedback output coupler mirror and additional intracavity elements. A simplified system without intracavity elements is analyzed initially, and an analytic expression for the mode solution is deduced. Addition of an intracavity lens is shown to permit enhancement of the quality of the phase-conjugation process as well as control of the mode size. The theoretical analysis is extended to model an experimental self-adaptive laser oscillator utilizing gain-grating formation in a solid-state Nd:YAG laser amplifier. Good agreement is found between the theory and the experimental results.