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Cryogenic solid-state laser materials offer many improvements in thermal, optical, structural, and lasing properties over their room temperature counterparts. As the temperature of Yb:YAG decreases from room to 80K it transitions from quasi-three-level lasing to a 4-level laser. In this study, we compare Yb:YAG thin-disk laser performance at room 293K and 80K. To achieve this direct comparison we have built two cooling systems based on R134A refrigerant and also on liquid nitrogen (LN 2 ). We have made an analytical calculation of the small signal laser gain that takes into account the spurious amplified spontaneous emission and photon re-absorption. The cold thin-disk laser clearly outperforms room temperature operation, and the theoretical results shows room temperature gain flattening.

At cryogenic temperatures, Yb:YAG behaves as a 4-level laser. Its absorption and emission cross-sections increase, and its thermal conductivity improves. Yb:YAG thin disk laser performance at room and cryogenic (80°K) temperatures will be presented. The Yb:YAG gain media is cooled using either a pressurized R134A refrigerant system or by a two-phase liquid nitrogen spray boiler. Interchangeable mounting caps allow the same Yb:YAG media to be switched between the two systems. This allows direct comparison of lasing, amplified spontaneous emission, and temperature performance between 20°C and -200°C.

No abstract