Optical properties of single doped Cr3+ and co-doped Cr3+-Nd3+ aluminum tantalum tellurite glasses

The optical properties for single doped Cr3+ and co-doped Cr3+-Nd3+ aluminum tantalum tellurite glasses have been studied as a function of temperature. For the single doped glass, the existence of two bands in the emission spectra at low temperature indicates the presence of two different sites for the Cr3+ ions, labelled as usual as low- and high-field sites. The broad band centred in the Near Infrared region, corresponds to low-field sites transition T-4(2) --> (4)A(2), and the narrow band centred at approximately 715 nm to the high-field sites transition E-2 --> (4)A(2). The emission intensity for both high- and low-field sites shows a strong decrease with increasing temperature, with the emission for the former sites vanishing at RT. In both cases the quenching observed with the increase of temperature can be ascribed to the presence of non-radiative relaxation mechanisms. Experimental observations for the co-doped glass show that both radiative and non-radiative energy transfer processes from Cr3+ to Nd3+ are present.