Spectroscopic properties of Er3+ in Ga2S3–GeS2–La2S3 glasses are investigated on the basis of the spontaneous emission probabilities calculated by the use of the Judd–Ofelt theory and lifetime data. Frequency upconversion spectra are also measured with excitation at 800 and 980 nm. The spontaneous emission probabilities are much larger than those of the other glass systems such as oxides and fluorides. This is mainly attributed to the large refractive indices of the sulfide glasses. The quantum efficiencies of I11/24 and F9/24 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 low phonon energies of the sulfide glasses. However, the quantum efficiency of the S3/24 level is less than one-half of the value in the fluoride glass. The nonradiative transition probability of the S3/24 level is much larger than the value which is evaluated from the multiphonon relaxation theory. This suggests the presence of the other nonradiative 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 F7/24 level is observed in addition to the red (665 nm) and the green (533 and 552 nm) emission bands.
Sulfide glasses of 50GaS3/2⋅20GeS2⋅20LaS3/2⋅10LnSn/2 (Ln=rare earth ions, n=2 for Eu and 3 for other ions) compositions have been prepared. The wavelength dispersions in the Faraday effect of the glasses have been examined. Glasses containing LaS3/2 and YS3/2 have positive Verdet constants in the wavelength region from 550 to 850 nm, and the magnitude of the Verdet constants decreases with increasing wavelength. On the other hand, the Verdet constants of glasses containing Eu2+ and Ce3+ are negative, and the absolute magnitude of the Verdet constants decreases with increasing wavelength. The effective transition wavelengths of glasses containing various paramagnetic rare-earth ions have been calculated based on the Van Vleck and Hebb theory. Factors determining the Verdet constants of these glasses are discussed.
Glasses containing Ei jj f to 7 cation mol% were prepared in the system of GaS3-GeS2-La2S3. Frequency upconversion spectra of F? jii the glasses were measured under the excitation at 800 nm and 980 urn. Green emission at 533 mu (llh1,2-'4I1i2) fld 552 iiiii ('3,2'h15/2), and red emission at 665 nm (4F912-'4I1512) WCTe observed. In addition to these emission bands, 497 inn emission assigned to the 4F712-4I1512 transition was observed. The spectral properties are analyzed from the view points oflow phonon energy property and high refractive index.
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