Generation of Super-Gaussian modes in Nd:YAG lasers with a graded-phase mirror

A dielectric graded-phase mirror was developed to change the intensity distribution of the fundamental mode in an Nd:YAG laser resonator to a top-hat profile. A super-Gaussian mode of the sixth order was generated by means of a graded-phase mirror with a simple ring-shaped phase step on a spherical reflector. The depth of the ring on the mirror was 90 nm. The graded-phase mirror was manufactured with an ordinary vapor deposition technique using an appropriate mask. Laser experiments with CW and repetitively pulsed diode-laser pumping were performed and compared. Slope efficiencies up to 19% were achieved. The experimental results are in excellent agreement with the theory.