Origin of Intrinsic Second-Harmonic Generation in Crystallized GeO2–SiO2 Glass Films

概要

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The origin and properties of second-harmonic generation (SHG) from crystalline particles and their crystalline phases in GeO2–SiO2 glass films were investigated. GeO2–SiO2 glass films with a thickness of approximately 5 μm were fabricated by the chemical vapor-phase deposition (CVD) method. Heat treatments in the temperature range of 1100–1260°C for durations of 2–8 h have been performed to crystallize the glass films. X-ray diffraction (XRD) peaks at around $2\theta=22$° in the crystallized GeO2–SiO2 films were observed, and the obtained XRD patterns in the glass films are exactly the same as those in ultraviolet (UV) poled GeO2–SiO2 glasses with a large second-order optical nonlinearity comparable to that in LiNbO3 crystals. Using a SHG microscopic technique, it has been found that the intensity of SHG emission from crystalline particles is clearly dependent on stress-induced optical retardation which is accompanied by the formation of crystalline particles of the \textit{pseudo-$\beta$-cristobalite} containing GeO2. In addition, a new technique for enhancing the intrinsic SHG by means of modification of defect states is demonstrated.
Published by the Japan Society of Applied Physics through the Institute of Pure and Applied Physicsの論文
2003-12-15