Maximum-Emission Principle and Phase Locking in Multimode Lasers

Abstract

In this paper the phase relationships between self-locked modes in lasers are investigated. The calculations are based on a self-consistency condition. The electric field in the cavity produces in the medium nonlinear polarization terms. These polarization terms may then be considered acting as source terms onto which the mode oscillations lock. The self-consistency condition imposed on the phases arises from the fact that the phase-locked modes must reproduce the originally assumed electric field. We find the calculated phase relationships in essential agreement with earlier predictions based on the maximum-emission principle. The latter principle assumes that the phase relations which maximize the total rate of-stimulated emission should grow most rapidly and should be the ones that establish themselves in lasers. The present paper gives additional evidence for the validity of the maximum-emission principle. In either calculation the basic physical mechanism that is responsible for the phase-locking effect is the nonlinear saturation in the laser medium or some saturable absorber.