Excitation and emission spectra of anti-Stokes luminescence of Tmsup3+/sup in glass span style="font-size:14.0pt;line-height:115%;font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman";color:black;mso-ansi-language:EN-IN; mso-fareast-language:EN-IN;mso-bidi-language:HI" lang="EN-IN"ceramics doped with various concentrations of sensitizer/span

摘要

In certain rare-earth doped glass ceramics luminescence emission has been observed at wavelength shorter than the exciting wavelength. This is known as anti-Stokes luminescence or up-conversion, which is due to accumulation of excitation energy by rare-earth ions. In Tmsup3+/sup and Ybsup3+/sup doped glass ceramics, Tmsup3+/sup acts as an activator and Ybsup3+/sup acts as a sensitizer. The activator concentration was kept constant at 0.2 mol% and the sensitizer Ybsup3+/sup concentration was varied from 0.0 mol% to 20 mol%. In emission spectra of glass ceramics doped with Tmsup3+/sup and Ybsup3+/sup, under infrared excitation span style="font-size:14.0pt;line-height:115%;font-family:" times="" new="" roman";="" mso-fareast-font-family:"times="" roman";color:black;mso-ansi-language:en-in;="" mso-fareast-language:en-in;mso-bidi-language:hi"="" lang="EN-IN"(966 nm) one peak of high intensity was found at different wavelengths between 400 to 500 nm for different concentrations of sensitizer. The peak is slightly shifted towards shorter wavelength with increasing concentrations of the sensitizer. This reveals that 3-photon up-conversion is prominent and presence of Ybsup3+/sup ions slightly shifts the energy levels of Tmsup3+/sup. In the excitation spectra of glass ceramics doped with Ybsup3+/sup and Tmsup3+/sup , initially the emission intensity increases with increasing wavelength, attains an optimum value for 920 nm, 930 nm, 950 nm and 960 nm and then it decreases with further increase in the wavelength. These photon energies may correspond to energy difference between levels of Tmsup3+/sup or Ybsup3+/sup. Both in the excitation spectra and emission spectra, initially the anti-Stokes luminescence intensity increases with sensitizer concentration, attains an optimum value and then it decreases with further increase in the sensitizer concentration. /span