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

The absorption spectra of titanosilicate glasses with the titanium concentration ~0.1 — 3% by weight were investigated in the wavelength range 225 — 460 nm. These glasses were synthesised in a steady laser plume in an atmosphere of air or nitrogen at normal pressure. Synthesis in these two atmospheres gave rise to Ti ions of different valence in the glasses. For the same Ti concentration the intensity of the characteristic absorption bands of titanium in its reduced states (Ti²⁺, Ti³⁺) with maxima at λ ~ 278 and 306 nm were 3 — 6 times higher when the synthesis took place in nitrogen. The enhancement of the 278 nm band was approximately half that of the band at 306 nm. Clear-cut strong absorption in the UV range at 260 — 280 nm as well as strong absorption in the visible range at 400 — 500 nm, observed for the first time for titanium-doped silica glass, were the results of a record-high concentration of Ti³⁺ ions, compared with the concentrations found in bulk glass samples prepared by other technologies such as melting, reduction of Ti⁴⁺ ions, and plasma hydrolysis.