Active mirrors for intra-cavity compensation of the aspherical thermal lens in thin-disk lasers

Abstract

With the development of the thin-disk laser, thermal lensing issues have been drastically reduced. However, fundamental mode operation at high output powers is still limited by severe efficiency reductions due to diffraction losses introduced by the temperature gradient at the boundary of the pump spot. To countervail these aspherical wavefront deformations, high-power laser mirrors featuring deformable surfaces have been developed. The surface of these mirrors resembles the shape of the thermally induced change of optical path length in the pumped laser crystal. The magnitude of the surface deformation can be actively controlled to provide optimal compensation at different power levels.

Laser-controlled adaptive optics for beam quality improvements in a multi-pass thin-disk amplifier

“…Good results 1 arXiv:1806.10796v1 [physics.optics] 28 Jun 2018 have also been demonstrated with a third, pneumatically adapted type of the deformable mirror. Inserted in the cavity of a thin disk laser this approach enables a near diffraction-limited beam quality of M 2 ¡ 1.4 at pump powers of about 2 kW and output powers of up to 815 W [11]. The drawback of the design is its limitation to the compensation of spherical wavefront distortions, thus higher order aberration terms can not be corrected for.…”