硅酸铅玻璃光敏性研究

Photosensitivity of Lead Silicate Glass

采用四倍频的Nd∶YAG脉冲激光 (波长 2 6 6nm ,脉宽 10ns)对氧化铅摩尔分数在 0 3至 0 5的硅酸铅玻璃体样品进行照射 ,并对照射前后样品的折射率及紫外可见吸收光谱进行了测量。研究发现不同能量密度的2 6 6nm激光照射硅酸铅玻璃体样品 ,会使样品的紫外可见吸收光谱产生不同的变化 :当 2 6 6nm激光能量密度较高时 (15 0mJ/cm2 ) ,样品在可见区域的吸收系数明显增大 ,样品表面会产生褐色斑点 ;而当 2 6 6nm激光能量密度较低时 (5 0mJ/cm2 ) ,尽管累计剂量较大 ,样品表面无斑点产生 ,吸收系数稍有增加 ,而折射率下降明显 ,最大Δn =- 0 .2 5± 0 .0 4。对氧化铅摩尔分数为 0 4 3的硅酸铅玻璃用不同能量密度的 2 6 6nm激光进行照射 ,发现当激光能量密度大于某一阈值时 ,样品在可见区域的吸收系数突然增大 ,这可能是由于硅酸铅玻璃吸收 2 6 6nm激光能量导致局部温度升高而引起玻璃结构改变所致。

UV-visible absorption spectra for the bulk lead silicate glass with different lead concentrations (mole fraction of PbO change from 0.30 to 0.50) were measured before and after irradiation with the frequency-quadrupled output of a Q -switched YAG laser (266 nm,10 Hz repetition rate). Different UV-visible spectra changes were observed after exposure to laser beam with different energy density. Exposed to the 266 nm laser beam with high energy density (150 mJ/cm 2),a visible brown spot could be seen on the surface of the exposed region,and the absorption coefficient increases evidently in wavelength range measured. Exposed to the 266 nm laser beam with low energy density (50 mJ/cm 2),no visible spot was observed,but the absorption spectra showed that the absorption coefficient increased slightly over the wavelength range observed,and the refractive index decreased evidently. The largest refractive index change Δ n is -0.25. Irradiating a sample with different energy density,the absorption coefficients in visible wavelength increased suddenly when the energy density was larger than a threshold value. This may be caused by the structural changes of lead silicate glasses induced by the increasing of the temperature in local region of the lead silicate glass.