CHARACTERIZATION AND ANALYSIS OF THE 4F-ELECTRONIC STATES OF TRIVALENT HOLMIUM IN YTTRIUM SCANDIUM GALLIUM GARNET

The electronic energy-level structure of Ho3+-doped yttrium scandium g allium garner (Ho:YSGG) is examined over the 0-41,600 cm(-1) spectral range. Data obtained from a combination of optical absorption, emissio n and emission excitation spectra measurements are used to locate and assign 232 of the 465 crystal-field (Stark) levels predicted to be spl it out of the 45 lowest-energy 4f(10)[SL]J multiplet manifolds of Ho3 in Ho:YSGG. The experimentally characterized energy-level structure i s analyzed in terms of a model Hamiltonian defined to represent the ma jor atomic-like (isotropic) interactions that contribute to the LS(ter m) and J(multiplet) structure of 4f(10)(Ho3+), as well as the anisotro pic crystal-field interactions that determine the splittings between S tark levels within the [SL]J multiplet manifolds of 4f(10)(Ho3+). A pa rameterized form of the model Hamiltonian is used to perform parametri c fits of calculated to observed energy-level data, and the results ob tained from these data fits show a root-mean-square deviation of <9 cm (-1) between the calculated and experimentally determined energies. Th e crystal-field interaction strengths and anisotropies determined in t he present study for Ho3+ in YSGG are compared to those determined pre viously for Ho3+ in YAG (yttrium aluminum garnet, Y3Al5O12) and for Er 3+ in both YSGG and YAG. These comparisons show small but clearly meas urable differences between the crystal-field interactions operative in YSGG vs YAG (for both Ho3+ and Er3+ dopant ions). The most significan t differences between the results obtained from comparative crystal-fi eld analyses of the Ho3+ vs Er3+ systems are seen in the two-electron correlation-crystal-field (CCF) contributions to energy-level structur e. Whereas CCF interactions appear to play a very important role in de termining the energy-level structures of several 4f(10)(Er3+) multiple t manifolds, no evidence is found for strong CCF effects on the energy -level structures of 4f(10)(Ho3+) multiplet manifolds. Copyright (C) 1 996 Elsevier Science Ltd