Absorption spectra and luminescence of oxygen-deficient centres in titanosilicate glass synthesised in a steady laser plume. II. Luminescence

The luminescence spectra of titanosilicate glasses, grown in a steady laser plume in an atmosphere of air or nitrogen at normal pressure, were investigated in the spectral range 260 — 500 nm. The luminescence was excited by the second harmonic of a cw Ar⁺ laser (λ = 257 nm) and was observed for glasses synthesised in air and nitrogen atmospheres throughout the investigated range of the titanium concentrations by weight (from ~0.1% to ~6%). When the titanium concentration was less than 1%, the luminescence spectrum of glass grown in a nitrogen atmosphere had a band with a maximum at λ ~ 280 nm associated with silicon oxygen-deficient centres and a correlated new strong band with a maximum at λ ~ 380 nm. An increase in the Ti concentration from ~0.1% to ~0.4% resulted in an exponential fall (by a factor of ~4) of the intensity of the 280 nm luminescence band accompanied by a rise of approximately 30% in the intensity of the luminescence in the 380 nm band. Luminescence in the range 350 — 500 nm was observed in glass grown in a nitrogen atmosphere when the titanium concentration was ~1% — 2%. Glass grown in air there had a wide band in the luminescence spectrum and its maximum was near ~440 nm (titanium concentration ~2%) and a band attributed to the Ti⁴⁺ luminescence (with a maximum near ~420 nm when the titanium concentration was 3% — 6%).