The non-radiative energy transfer in high acceptor concentration codoped Nd,Ho:YAG and Nd,Er:YAG

For three luminescent laser crystals it is found that the dipole-dipole interaction between donor-acceptor pairs at short distances is dominated by higher order multipolar interactions. This effect is reflected as a fast initial decay in the donor emission transient of the codoped systems Nd,Ho:YAG and Nd,Er:YAG at high acceptor concentrations. The effect is enhanced as the acceptor concentration is increased. At long times the donor emission transients show the effects of the dipole-dipole interaction between donor-acceptor pairs, that is, the long range multipolar interaction drives the non-radiative energy transfer. The Monte Carlo model shows these effects for the non-radiative energy transfer process applied to those luminescent systems. For this model the discreteness of the YAG lattice is kept since dopants are randomly placed into the 24c sites. The donor emission transients are obtained by calculating the probabilities of the events that occur after a donor is excited.