Spectral analysis and energy-level structure of Er~(3+)(4f~(11)) in polycrystalline ceramic garnet Y_3Al_5O_(12)

摘要

Absorption spectra obtained between 1550 and 440 nm and fluorescence spectra obtained between 1700 and 1500 nm are reported in a comparative spectroscopic study of polycrystalline ceramic Y_3Al_5O_(12) (YAG) and single-crystal laser rod YAG, both containing 50 at.% Er~(3+) as a dopant in the garnet host. The spectra are observed in both samples at temperatures between 8K and room temperature. The detailed splitting of individual multiplet manifolds, ~(2s+1)L_J, Er~(3+)(4f~(11)), by the crystalline electric field is similar in both the ceramic sample and the single-crystal laser rod. With few exceptions, there is little shift in energy (few wave numbers) of individual Stark levels within a manifold, between dilute and concentrated Er~(3+) samples. This is not too surprising since Y_3Al_5O_(12) and Er_3Al_5O_(12) form a solid solution with the majority of Er~(3+) ions occupying cation sites having D_2 symmetry in the garnet lattice over the entire solid solution range. As a check on the observed manifold splittings of Er~(3+) in ceramic YAG, we compared the present results to the calculated splitting that several of us reported earlier for Er~(3+) in single-crystal YAG. To within the standard deviation reported earlier, the present results agree with that calculation. Thus, one set of atomic and crystal-field parameters describes the splitting of the Er~(3+) energy levels in either the ceramic or single-crystal host for Er~(3+) in D_2 sites.