Thin-disk laser scaling limit due to thermal lens induced misalignment instability.

We present a fundamental obstacle in power scaling of thin-disk lasers related to self-driven growth of misalignment due to thermal lens effects. This self-driven growth arises from the changes of the optical phase difference at the disk caused by the excursion of the laser eigen-mode from the optical axis. We found a criterion based on a simplified model of this phenomenon, which can be applied to design laser resonators insensitive to this effect. Moreover, we propose several resonator architectures that are not affected by this effect.