Md. Seltzer et al., MULTISITE OPTICAL-SPECTRA AND ENERGY-LEVELS OF TRIVALENT THULIUM IONSIN YTTRIUM SCANDIUM GALLIUM GARNET, Journal of applied physics, 74(4), 1993, pp. 2821-2829
Intrinsic structural disorder in scandium-substituted garnets, attribu
ted to mixed occupancy o certain sites in the crystal lattice by diffe
rent cations, has direct consequences for the optical spectra of rare-
earth activator ions dispersed over multiple sites. In trivalent thuli
um-doped yttrium scandium gallium garnet (Tm3+:YSGG), site-selective l
aser excitation spectra reveal the presence of Tm3+ ions in regular D2
sites, disturbed regular sites, and in octahedral C3i sites. Absorpti
on spectra obtained at 4 K between 0.26 and 1.85 mum are broader than
those observed in more-ordered crystal hosts and include structure att
ributed to Tm3+ ions in sites of other than D2 symmetry. A crystal-fie
ld splitting calculation was carried out in which a parametrized Hamil
tonian (including Coulombic, spin-orbit, and crystal-field terms for T
m3+ ions in D2 symmetry) was diagonalized for all manifolds of the Tm3
+ (4f12) configuration. The rms deviation between 52 experimental and
calculated Stark levels of Tm3+ in regular D2 sites was 5 cm-1.