Characterization of Pt4+ in alumino-metaphosphate laser glasses

The pt(4+) optical spectra (16 600-50 000 cm(-1)) in a series of alkali/alkaline alumino-metaphosphate glasses are reported. The four observed spectral bands are assigned to the d-d transitions from the (1)A(1g) ground state to the T-3(1g) (similar to23 500 cm(-1)), T-3(2g) (similar to28 000 cm(-1)), T-1(1g) (similar to33 300 cm(-1)) and T-1(2g) (similar to40 000 cm(-1)) excited states assuming pt(4+) resides in a distorted octahedral site. The absorption band intensities are found to exist in two groups, with the low compositionally averaged modifier field strength (<3.5 Angstrom(-2)) having the greater absorption intensities. The ligand splitting energy and Racah parameter B vary between similar to38 000 and 40 000 cm(-1) and between similar to435 and 650 cm(-1), respectively, depending on the choice of modifier. The pt(4+) absorption coefficient, alpha, at 25 000 cm(-1) is correlated with the platinum concentration (ppm(w)) in a potassium magnesium-alumino-metaphosphate glass by the equation: [Pt] ppm(w) = 526alpha (cm(-1)). A comparison of relative Pt uptake during melting shows that the rare-earth doped potassium magnesium alumino-phosphate melt has the greatest uptake and is approximately 25 times greater than the concentration reported for the commercial silicate laser glass, ED-2. The effect of pt(4+) (0-860 ppm(w)) on fluorescence quenching rate from the Nd3+ F-4(3/2) state is small (k(A) approximate to 0.3 Hz/ppm(w)) in agreement with predictions based on the Forster-Dexter theory for dipolar energy transfer. (C) 2003 Elsevier Science B.V. All rights reserved.