Custom laser resonators using graded-phase mirrors

The authors derive a simple algorithm for designing a stable graded-phase-mirror resonator. First, the desired output beam profile of the fundamental mode is propagated into the laser medium. The wavefront is then extracted and serves to determine the appropriate phase profile of the mirror. The diffractional analysis of the resonator using this graded-phase mirror indicates a very low loss for the fundamental mode with a very large discrimination of higher modes. Practical design parameters such as the geometric factor, the Fresnel numbers, and phase profile perturbations are discussed. The authors conclude that this type of resonator can increase significantly the mode volume and favor the single-mode operation of laser systems relying on a stable resonator geometry