Study of energy transfer in gadolinium–gallium garnet crystals doped with Yb3+ and Ho3+ ions

The luminescence kinetics of Yb³⁺ donors and Ho³⁺ acceptors is quantitatively studied in gallium–gadolinium garnet (GGG) crystals doped with Yb³⁺ and Ho³⁺ ions. It is shown that the sensitisation of transitions in Ho³⁺ ions occurs due to migration-accelerated (hopping) energy transfer. The microparameters of donor–donor energy transfer are determined at 300 and 77 K. The microparameters of donor–acceptor energy transfer are found at the same temperatures at the first stage of successive sensitisation (resulting in the population of the ⁵I₆ state of Ho³⁺ ions) and at the second stage of successive sensitisation of the ⁵S₂, ⁵F₄→⁵I₈ transition in Ho³⁺ ions. At the second stage of sensitisation, the values of the microparameter of reverse energy transfer are also determined. The possibility of obtaining lasing at sensitised transitions in Ho³⁺ ions in Yb³⁺:Ho³⁺:GGG crystals pumped into the absorption band of Yb³⁺ ions is discussed.