飞秒激光诱导玻璃内Ba2TiSi2O8晶体的析出

使用聚焦后的800nm，150fs，250kHz的高重复频率飞秒脉冲激光器能够在BaO-TiO₂-SiO₂组分的玻璃内部三维选择性地诱导Ba₂TiSi₂O₈晶体的析出. 发光光谱显示这种晶体把入射的800nm光转化成了400nm的蓝光，因此这种析出的晶体具有非线性倍频特性. 通过拉曼光谱测定，在当前的玻璃组分中析出的晶体是Ba₂TiSi₂O₈. 研究表明，经250kHz的飞秒激光辐照一段时间后，在玻璃内部由于脉冲能量的连续沉积会使得激光辐照区域出现热积累效应，因此,该辐照区域的温度会不断升高以致超过玻璃析晶温度，最终诱导玻璃熔融析晶. 此外，对飞秒激光辐照区域不同部位进行拉曼光谱检测，结果表明：在整个区域Ba₂TiSi₂O₈晶体的析出呈现中间比外围明显的分布特点，因此晶体析出与辐照形成的温度梯度场有密切关系.

Femtosecond Laser Induced Ba2TiSi2O8 Crystal Precipitation in Glass

Ba₂TiSi₂O₈ crystal was space-selectively precipitated in a 33.3BaO-16.7TiO₂-50.0SiO₂ glass sample by using a high repetition femtosecond laser with 800nm, 150fs and 250kHz. After the femtosecond laser irradiated for a period of time, the luminescence of the focused point could chang from 800nm red light to 400nm blue one due to second-order optical nonlinearity of the precipitated crystal. Raman spectra show Ba₂TiSi₂O₈ crystal is formed. During the femtosecond laser irradiation, heat accumulation effect occurs in the irradiated region by continuously absorbing pulse energy, and the glass would be heated to its crystallization temperature, therefore Ba₂TiSi₂O₈ may grow or precipitate in the crystallized region. Furthermore, the Raman spectra at different positions of the irradiated region demonstrate that Ba₂TiSi₂O₈ crystal grows more effectively in the center compared with that in the outers. This result is agreeable with the femtosecond laser induced temperature distribution because the temperature increases more quickly in the focused region.