High-resolution spectroscopy and emission decay in concentrated Nd:YAG ceramics

The high-resolution spectroscopic and emission-decay investigation of highly concentrated (up to 9 at. %) Nd:YAG ceramics indicates that the state of the Nd3+ ion in these materials is similar to that of diluted crystals. The increased relative intensities of the spectral satellites connected with ensembles of Nd ions in near-lattice sites at high Nd concentrations CNd is consistent with the predictions of the statistics of the random placement of these ions at the available lattice sites. The room-temperature transmission spectra show that the resonant pump in the emitting level  4F3/2, including the hot-band pump Z2→R1 and Z3→R2, can be efficient at high CNd, with important effects in the reduction of the pump quantum defect and of the corresponding heat generation under the pump. The accelerated  4F3/2 emission decay at high CNd is consistent with the increased efficiency of the energy transfer, including the contribution of migration-assisted transfer processes. The calculated emission quantum efficiency η and the figure of merit ηCNd indicate that the concentrated Nd:YAG components can be used for construction of efficient solid-state lasers in free-generation or low-storage regimes, and, coupled with the hot-band resonant pump in the emitting level, they could enable the scaling of Nd:YAG lasers to high powers.