Controlled Growth of SnO2 Nanocrystals in Eu3+-Doped SiO2−SnO2 Planar Waveguides: A Spectroscopic Investigation

We report on the fabrication of Eu3+-doped SiO2−SnO2 low-loss (0.8 dB/cm at 632.8 nm) glass-ceramic planar waveguides, fabricated by the sol−gel technique and dip-coating processing. The effects of heat treatments on the growth and evolution of SnO2 nanocrystals in the matrix were investigated using different spectroscopic tools. In situ high-temperature X-ray diffraction allowed for the determination of the crystallization temperature and confirmed the formation of tetragonal rutile SnO2 crystals. The effect of crystallization on the optical properties and on the photoluminescence of Eu3+ ions was also studied. Low-frequency Raman scattering was successfully used to determine the crystal size, and the results obtained were found to be consistent with transmission electron microscopy measurements. The breakage of Si−O−Sn linkages during the formation of SnO2 nanocrystals in the matrix was investigated by Fourier-transform infrared spectroscopy.