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Abstract: We report on the precipitation of Si nanocrystals inside a borosilicate glass by using an 800nm, 250kHz femtosecond laser irradiation, which was confirmed with X-ray diffraction, Raman spectra and transmission electron microscopy analyses. Refractive index profile reveals that the refractive index of the Si nanocrystals precipitated region increased up to 8.7% in comparison with that of the unirradiated area, leading to a large diffraction efficiency of the fabricated dot structure. Furthermore, the third-order optical nonlinearity of the Si nanocrystals precipitated glass is greatly enhanced based on the Z-scan measurement. These results may find applications for the fabrication diffractive optical devices and optical switches. [Copyright &y& Elsevier]

Abstract: The doped Eu3+ ions can be partly reduced to Eu2+ in a series of MO–B2O3: Eu (M=Ba, Sr, Ca) glasses synthesized in air atmosphere, but not in the 12CaO–7Al2O3: Eu glass. The different redox-behavior of Eu ions in these two glass systems is attributed to the different host optical basicity. It is found that a lower valence state of Eu2+ is more favorable in acidic glasses, which have lower optical basicities. A notion of the critical value of optical basicity is introduced empirically, which can be used as a guide for the selection of glass composition suitable to incorporate Eu2+ for luminescence. [Copyright &y& Elsevier]