Preparation and optical properties of boron-doped Si-Na-Al-Zn photo-thermal-refractive glass

Photo-thermo-refractive (PTR) glass, which has the advantages of high refractive index modulation value, large working bandwidth and wide environmental adaptability, is an excellent material for preparing volume Bragg grating (VBG). However, the application of PTR glass is limited because of its high melt processing temperature and high optical loss. The introduction of boron into PTR glass can significantly reduce the melting temperature. In this study, boron-doped Si-Al-Na-Zn PTR glass was prepared at a low temperature by the high-temperature melting method, and its temperature–viscosity relationship, heat treatment procedure and optical properties were investigated. The results show that the introduction of boron into PTR glass can significantly reduce the high-temperature viscosity of PTR glass. The melting temperature is lower than 1,400 °C, and the optimum nucleation and crystallisation temperatures are 490 °C and 590 °C, respectively. The optical transmittance of UV-exposed and heat-treated glass is more than 90%, which indicates its excellent optical properties and its applicability for use in preparing VBG with high diffraction efficiency and low optical loss. (paper)