Temperature-dependent lasing and spectroscopy of Yb:Y2O3 and Yb:Sc2O3

Spectroscopic and laser properties of Yb3+ in ceramic Y2O3 have been studied at room and cryogenic temperatures. Laser performance is very substantially improved by cooling to liquid nitrogen temperature, primarily due to the great reduction in ground state absorption that permits laser operation on the much stronger 1030-nm emission line rather than the 1077-nm line. The 976-nm “zero line” is observed to become much weaker as the temperature is reduced. Several models for this behavior are considered, but none adequately explains this surprising result. Spectroscopy of Yb:Sc2O3 indicates that it is likely to be an even better cryogenic gain material, given samples of comparable optical quality.