A thin disk laser includes a thin disk of a host material incorporating a laser gain medium. The disk has opposite first and second surfaces, at least one of which is non-planar. The first surface is coated with a high reflectivity coating. The second surface has an anti-reflection coating thereon. The shape and mounting of the laser is such that mismatch of the coefficients of thermal expansion between the disk laser and the mount does not affect scaling of the laser to larger size disks for higher power lasers.