Interaction of Er3+ ions in Er-doped calcium — niobium — gallium garnet crystals

The processes of nonradiative energy transfer in calcium — niobium — gallium garnet (CNGG) crystals doped with Er³⁺ ions are studied. It is found that the energy of erbium ions in the Er:CNGG crystal with the erbium atomic concentrations C_Er=6% and 11% is transferred via the nonradiative co-operative processes ⁴I_11/2→ ⁴I_15/2, ⁴I_11/2→ ⁴F_7/2, ⁴I_11/2→ ⁴I_15/2, ⁴I_13/2→ ⁴F_9/2; and ⁴I_13/2→ ⁴I_15/2, ⁴I_13/2→ ⁴I_9/2, whose efficiency increases with increasing intensity of exciting radiation. It is shown that the cross-relaxation processes ⁴S_3/2→⁴I_9/2, ⁴I_15/2→⁴I_13/2, whose intensity depends on the concentration of Er³⁺ ions, are characteristic for Er:CNGG crystals with the Er atomic concentration above 1%.