Er3+ in Sc2O3 and Y2O3: Spectroscopy to elucidate laser behavior

Er:Sc2O3 exhibits spectroscopic properties that give surprising cryogenic laser behavior (particularly broad zero-line absorption, and a switch to a shorter laser wavelength for temperatures above 110 K). We find that spectroscopic comparison of this material with Er:Y2O3 clarifies the subtle features responsible for this laser behavior.