Optical second-order nonlinearity of transparent glass-ceramics containing BaTiO 3 precipitated via surface crystallizat
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Optical second-order nonlinearity of transparent glass-ceramics containing BaTiO3 precipitated via surface crystallization Aiko Narazaki, Katsuhisa Tanaka, and Kazuyuki Hirao Department of Material Chemistry, Graduate School of Engineering, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan (Received 10 February 1999; accepted 21 June 1999)
Second-harmonic generation of transparent glass-ceramics containing BaTiO3 crystalline phase was investigated using Maker fringe method. When 15BaO ⭈ 15TiO2 ⭈ 70TeO2 glass was heat-treated at 415 °C for 0.5–12 h, (101)- or (110)-oriented BaTiO3 crystals precipitated in the near-surface region. The resultant glass-ceramics exhibit second-harmonic generation. Variation of second-harmonic intensity with angle of incidence, i.e., the Maker fringe pattern changes drastically with an increase in heat treatment time and temperature. No second-harmonic signal was detected in glass-ceramics derived from 15SrO ⭈ 15TiO2 ⭈ 70TeO2 glass. These facts suggest that BaTiO3 crystal is responsible for the second-order nonlinear phenomenon, although its structure is closer to cubic than tetragonal according to x-ray diffraction measurements. In order to estimate second-order nonlinear optical coefficient d (2), Maker fringe patterns of the BaTiO3-containing glass-ceramics were analyzed. For the glass-ceramic after heat treatment for 0.5 h, d33 and thickness of BaTiO3-crystallized layer, L, are 3.65 pm/V and 3.43 m, respectively. The value of second-order nonlinear optical coefficient is comparable to those of BaTiO3 films prepared via metalorganic chemical vapor deposition and pulsed-laser deposition. On the other hand, the glass-ceramic heat-treated for 12 h exhibits d15 ⳱ 0.31 pm/V and L ⳱ 300 m. The thickness of the layer active in second-order nonlinearity evaluated from the Maker fringe pattern is coincident with the observation by scanning electron microscopy.
I. INTRODUCTION
Transparent glass-ceramics containing ferroelectric crystalline phases have been attracting considerable attention because of high optical second-order nonlinearity as well as easiness to fabricate.1–5 For the purpose of achieving large second-order nonlinearity and high transparency simultaneously, it is desirable that the difference in refractive index between glass matrix and crystallite is small enough to reduce the light scattering caused by boundaries. Komatsu et al.6 succeeded in preparing transparent glass-ceramics containing BaTiO3 crystallites from tellurite-based glasses; the refractive indices of tellurite glass matrix and BaTiO3 are almost the same. Tanaka et al.4,5 subsequently found that surface crystallization of BaTiO3 as well as other crystalline phases occurred in the same glass system and observed secondharmonic generation in the glass-ceramics, although the ratio of lattice parameters, c/a, of BaTiO3 crystals precipitated was closer to the value of the paraelectric cubic phase than that of the ferroelectric tetragonal phase as 3640
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