Abstract

The lasing transition between the ⁴I_11/2 and ⁴I_13/2 of Er³⁺ in YAG is self-terminating due to the significantly longer lifetime of ⁴I_13/2. This paper describes the codoping of Er:YAG with Eu and Tb as deactivator ions to reduce this undesirable effect by energy transfer between the ⁴I_13/2 of Er³⁺ and the codopant ions. Unique grouping of levels in Eu³⁺ and Tb³⁺ provide numerous levels between ⁴I_13/2 and the ground state for fast multiphonon relaxation but none near ⁴I_11/2. Crystals of 16% Er:YAG codoped with different Eu and Tb concentrations were grown by the laser-heated pedestal growth technique for measuring lifetimes of excited Er³⁺ ions. We found that with both Eu and Tb, doping at ~1% increased the ratio of upper to lower state lifetimes from 0.02 to better than 0.3. Higher doping did not increase this ratio as quenching of ⁴I_11/2 became significant. This is likely due to cross relaxation involving ground state ions of the codopant. Although unable to achieve a ratio of unity and above, codoping Er:YAG should still lead to improvement in pulsed laser performance.

© 1989 Optical Society of America