DE 19860921 A UPAB: 20000823 NOVELTY - The active laser medium comprises a cooling surface (2) which lies in thermal contact with a heat sink (1) to cool the medium. The laser medium is held surrounded by a thermally insulating covering. The thermal conduction within the laser medium is essentially in the direction of the cooling surface. The propagation direction of the laser beam to be amplified lies essentially parallel to the temperature gradient in the laser medium. USE - Optically pumped solid-state amplifier. ADVANTAGE - Highly efficient laser operation with high beam quality.