Role of undoped cap in the scaling of thin-disk lasers

The optimum design of a powerful thin-disk laser implies a compromise between amplified spontaneous emission (ASE), overheating, and the round-trip losses. The power enhancement of a composite thin-disk laser made of an undoped layer bonded over a thin active layer to reduce ASE losses is estimated analytically. Scaling laws for the parameters of a disk laser are suggested for cases both with and without an anti-ASE cap. Predictions of the maximal power achievable for a given laser material are compared to the published experimental data. The anti-ASE cap allows an increase of the maximal output power proportional to the square of the logarithm of the round-trip loss. (C) 2008 Optical Society of America.