LUMINESCENCE OF CR3+ AND ENERGY-TRANSFER BETWEEN CR3+ AND ND3+ IONS IN YTTRIUM-ALUMINUM-GARNET

The luminescence properties of Cr3+ ions and the energy transfer between Cr3+ and Nd3+ ions have been studied quantitatively in yttrium aluminum garnet (YAG). The energy level diagram and the emission spectrum of T-4(2)-->(4)A(2) transition of Cr3+ ions were calculated in this crystal using the single-configurational-coordination model and the absorption data. Our calculated Delta value (the energy difference between the (2)E zero-vibrational level and the crossover point of (2)E and T-4(2) states, similar to 730 cm(-1) at room temperature, in contrast to the previously estimated value of similar to 1000 cm(-1), accounts for a variety of experimental results more satisfactorily. Both the T-4(2) and (2)E states of Cr3+ ions were found to contribute to the energy transfer to Nd3+ ions. The contribution of the former dominates at high temperatures and the latter at low temperatures. The thermal population distribution between the T-4(2) and (2)E states of Cr3+ ions was shown to be responsible for the temperature dependences of the Cr3+ luminescence properties and the Cr3+ to Nd3+ energy transfer processes. An electric dipole-dipole interaction mechanism was found to be adequate to describe the energy transfer process for temperatures up to about 400 K. (C) 1995 American Institute of Physics.