Theory of spontaneous mode locking in lasers using a circuit model

A theory is presented of mode locking in lasers with dispersion in the resonator and a saturable absorber, using as a starting point a circuit representation of the physical processes in the system. A set of equations for mode amplitudes and phases is obtained that entails no significant approximations and is suitable in form for an iterative method of solution. The specific advantages of the method include 1) treating the problem without limiting the order of interaction in the absorber, and 2) introducing a circuit model that allows some intuitive approximations. A general expression for mode phases in a certain situation is developed as an example and the results are compared with published material.