OPTICAL-TRANSITIONS AND FREQUENCY UP-CONVERSION EMISSION OF ER3-GES2-LA2S3 GLASSES( IONS IN GA2S3)

Spectroscopic properties of Er3+ in Ga2S3-GeS2-La2S3 glasses are inves tigated on the basis of the spontaneous emission probabilities calcula ted by the use of the Judd-Ofelt theory and lifetime data. Frequency u pconversion spectra are also measured with excitation at 800 and 980 n m. The spontaneous emission probabilities are much larger than those o f the other glass systems such as oxides and fluorides. This is mainly attributed to the large refractive indices of the sulfide glasses. Th e quantum efficiencies of I-4(11/2) and F-4(9/2) levels are comparable or larger than the typical values of Er3+ in, a fluoride glass. This is a consequence of the large spontaneous emission probabilities and l ow phonon energies of the sulfide glasses. However, the quantum effici ency of the S-4(3/2) level is less than one-half of the value in the f luoride glass. The nonradiative transition probability of the S-4(3/2) level is much larger than the value which is evaluated from the multi phonon relaxation theory. This suggests the presence of the other nonr adiative relaxation process in addition to the multiphonon relaxation. This process is considered to be the energy transfer from the excited Er3+ to, the band-gap excitation of the matrix glass. In upconversion spectra, the 497 nm emission from the F-4(7/2) level is observed in a ddition to the red (665 nm) and the green (533 and 552 nm) emission ba nds. (C) 1998 American Institute of Physics.