Laser resonators using a graded-phase mirror

We propose a new approach to improve the mode beamwidth and power efficiency of laser systems relying on a stable resonator geometry. The algorithm is simple and straightforward. The desired output beam profile (e.g. super-Gaussian) is propagated in the intracavity medium, and its wavefront is then determined for the design of a graded-phase mirror. A numerical analysis of the influence of practical design parameters, such as geometrical factor and Fresnel numbers, indicates a very low loss for the fundamental mode as well as a very high discrimination of higher modes. It has also been found that this type of resonator is not very sensitive to various types of perturbation. In particular, gain saturation has little effect on the mode shapes and the desired fundamental mode remains predominating. Phase perturbations (including possible thermal lensing effects) have also been considered. We conclude that this resonator can increase significantly the mode volume and favor the single-mode operation of laser systems using a stable configuration.