OPTICAL-SPECTRA, ENERGY-LEVELS, AND EMISSION INTENSITY CALCULATIONS OF TRIVALENT THULIUM IONS IN GADOLINIUM SCANDIUM GALLIUM GARNET

Absorption spectra of trivalent thulium ions in gadolinium scandium ga llium garnet are reported between 1.9 and 0.25 mu m at 4 K. Laser-indu ced fluorescence was observed at 4 K from the D-1(2), (1)G(4), and H-3 (4) (4 and 300 K) manifolds. Site-selective excitation experiments rev eal large fractions of thulium ions in both regular D-2 sites and alte rnate sites. A crystal-field splitting calculation was carried out in which a parameterized Hamiltonian (including Coulombic, spin-orbit, an d crystal-field terms in D-2 symmetry) was diagonalized for all multip let manifolds of the Tm3+ (4f(12)) configuration. The rms deviation be tween 56 experimental and calculated Stark levels was 10 cm(-1). Calcu lations were carried out to predict branching ratios for emission from the H-3(4) manifold to the H-3(5), F-3(4), and H-3(6) manifolds, as w ell as line-to-line transition probabilities for transitions between t he H-3(4) manifold and the H-3(5) manifold.