Abstract

Strong UV emission has been observed in crystals of CsMgCl₃ doped with Er³⁺ ions when pumped with 546 to 550 nm wavelengths. CsMgCl₃ crystals exhibit a chain structure where two Er³⁺ ions replace three Mg²⁺ ions in the chain, preserving the local charge balance forming discrete defined pairs. The UV emission is observable at temperatures between 10 and 297 K. At 10 K the intensity of the UV emission is comparable to the emissions from the pumped state. The experiments performed in our lab show that the up-conversion is a second order process due to energy transfer between simultaneously excited Er³⁺ pairs involving two ⁴S_3/2 states, raising the energy of one Er³⁺ sight to twice the energy (⁴G_9/2). Energy migration through the crystal and other doubly excited pairs also results in weak up-conversion emissions. The strongest UV emissions are due to transitions from ⁴G_9/2 to ⁴I_13/2(338 nm) and ⁴G_11/2 to ⁴I_13/2 (377 nm). Because of thermal population of the sublevels within the ground state (⁴I_15/2) manifold, a number of red shifted features (hot bands) appear in the excitation spectrum as the temperature is raised from 10 to 297 K.

© 1992 Optical Society of America