Frequency upconversion of cw infrared radiation at 1.06 μm into the visible in Er3+/Yb3+-codoped Ga2S3:La2O3 chalcogenide glass samples is presented. Intense green and red emission bands around 530, 555, and 670 nm, respectively, are observed in addition to near-infrared 830 and 925 nm less intense signals. Energy transfer processes and nonradiative phonon-assisted decays account for the population of the H211/2, S43/2, and F49/2 emitting levels. The dependence of the red emission with the Yb3+ concentration is also analyzed. The potential application of the Er/Yb-codoped Ga2S3:La2O3 glass for upconversion based optical devices is discussed.

Upconversion fluorescence emission of Er3+/Yb3+-doped Bi2O3–Na2O–Nb2O5–GeO2 heavy metal glass samples excited at 1.06 μm is experimentally investigated. The results reveal the existence of intense emission bands centered around 520, 545, and 655 nm. The germano-niobate based host glass presents high transparency in the region of 400–2700 nm, the capability of incorporating high dopant concentrations, high melting temperature, and large resistance to atmospheric moisture. The observed intensity of the green fluorescence emission, suggested that the niobium based host glass material plays an important role in the efficiency of the upconversion process. Emission lines centered at 425, 483, 503, 608, and 628 nm were also observed.

Infrared-to-visible upconversion emission enhancement through thermal effects in Yb 3ϩ -sensitized Pr 3ϩ -doped fluoroindate glasses excited at 1.064 m is investigated. A twentyfold increase in the 485 nm blue emission intensity as the sample temperature was varied from 20 to 260°C was observed. The visible upconversion fluorescence enhancement is ascribed to the temperature dependent multiphonon-assisted anti-Stokes excitation of the ytterbium sensitizer and excited-state absorption of the praseodymium acceptor. A model based upon conventional rate equations considering a temperature dependent effective absorption cross section for the 2 F 7/2 → 2 F 5/2 transition of the Yb 3ϩ and 1 G 4 → 3 P 0 excited-state absorption of the Pr 3ϩ , agrees very well with the experimental results.

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