| Abstract
| - Fresnoite, Ba2TiSi2O8, is a ferroelectric crystal with a very large second-order optical nonlinearity. X-raydiffraction analysis and Raman spectra indicate that Ba2TiSi2O8 crystals are precipitated in the glass-ceramicsafter heat treatment at 750 °C for 2 h. Near-infrared to visible upconversion luminescence is observed inSm3+-doped glass and glass-ceramic samples under infrared femtosecond laser irradiation, and the Sm3+-doped glass-ceramic shows strongly enhanced mutiphoton absorption induced luminescence and improvedsaturate threshold compared with the as-prepared glass. The mechanisms of the observed phenomena arediscussed.
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