Abstract: The Judd-Ofelt parameters Ωλ(λ=2,4,6) have been calculated for Er3+ ions in Er3+/Yb3+ co-doped LiNbO3 and YVO4 crystals at room temperature, together with the radiative transition probabilities, non-radiative transition probabilities and resonant transition probabilities of Er3+ ions. Taking into account the energy transfer from Yb3+ to Er3+, the rate equations are given for Er3+ ions. We have obtained from a solution of the rate equations that Er3+/Yb3 co-doped YVO4 crystal is more efficient for up-converted 550nm Er3+ emission than Er3+/Yb3+ co-doped LiNbO3 crystal, which is consistent with our observation.

Key words: The Judd-Ofelt parameters Ωλ(λ=2,4,6) have been calculated for Er3+ ions in Er3+/Yb3+ co-doped LiNbO3 and YVO4 crystals at room temperature, together with the radiative transition probabilities, non-radiative transition probabilities and resonant transition probabilities of Er3+ ions. Taking into account the energy transfer from Yb3+ to Er3+, the rate equations are given for Er3+ ions. We have obtained from a solution of the rate equations that Er3+/Yb3 co-doped YVO4 crystal is more efficient for up-converted 550nm Er3+ emission than Er3+/Yb3+ co-doped LiNbO3 crystal, which is consistent with our observation.