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

The luminescence properties of Cr3+ ions and the energy transfer betwe en Cr3+ and Nd3+ ions have been studied quantitatively in yttrium alum inum 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 cr ystal using the single-configurational-coordination model and the abso rption 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 t o the previously estimated value of similar to 1000 cm(-1), accounts f or 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 energ y transfer to Nd3+ ions. The contribution of the former dominates at h igh temperatures and the latter at low temperatures. The thermal popul ation 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+ l uminescence properties and the Cr3+ to Nd3+ energy transfer processes. An electric dipole-dipole interaction mechanism was found to be adequ ate to describe the energy transfer process for temperatures up to abo ut 400 K. (C) 1995 American Institute of Physics.