Eigenmodes of a Symmetric Cylindrical Confocal Laser Resonator and Their Perturbation by Output-Coupling Apertures

Abstract

Using a numerical technique which is different from the iteration method of Fox and Li and which is more suitable for the analysis of high-order modes, we have calculated the diffraction losses and the field distributions at the reflectors of the low-loss modes of a symmetric confocal resonator for Fresnel numbers 0.6 ≦ Nm≦ 2.0. We have also computed the modifications which result when the two end reflectors are perturbed by circular output-coupling apertures centered on the cavity axis. For a range of small but useful aperture Fresnel numbers N0the aperture diffraction losses can be estimated by first-order perturbation theory from the finite-Nmresults appropriate to N0&equal; 0. Such estimates fail for those larger Fresnel numbers N0for which the mode intensity patterns are significantly distorted at the reflectors by the finite coupling apertures.