Aperture guiding in quasi-three-level lasers

Aperture guiding, as opposed to thermal waveguiding, is shown to be the dominant mechanism for cavity mode stabilization in a quasi-three-level Yb:YAG laser in a flat-flat resonator. Excellent agreement is obtained between the experimental and modeled spot sizes in this laser when aperture guiding is included in the model. The models show that the spot size is insensitive to the exact form of the dependence of the transmission of the aperture on the transverse dimension. This finding is expected to affect other quasi-three-level lasers.