摘要:
研究了不同剂量的60 kW高功率脉冲电子束辐照对高纯熔石英玻璃的微观结构、光学性能和激光损伤特性的影响规律.光学显微图像表明,辐照后熔石英样品由于热效应导致表面破裂,裂纹密度和尺寸随辐照剂量增加而增大,采用原子力显微镜分析表面裂纹的微观形貌,裂纹宽度约1μm,同时样品表面分布着大量尺寸约0.1—1μm的碎片颗粒.吸收光谱测试表明,所有样品均在394 nm处出现微弱的吸收峰,吸收强度随着电子束辐照剂量增大呈现先增加后减小的趋势.荧光光谱测试发现辐照前后样品均有3个荧光带,分别位于460,494和520 nm,荧光强度随辐照剂量的变化趋势与吸收光谱一致.利用355 nm激光研究了不同剂量电子束辐照对熔石英激光损伤阈值的影响,结果表明熔石英的损伤阈值随着辐照剂量的增加而降低.在剂量较低时,导致熔石英激光损伤阈值下降的原因主要是色心缺陷；剂量较高时,导致损伤阈值降低的原因主要是样品表面产生的大量微裂纹和碎片颗粒对激光的调制和吸收.
Abstract:
A 60 kW electron beam is used to study the microstructure and optical property evolutions as well as laser induced damage threshold of fused silica after irradiation at room temperature. Optical microscopic results indicate that cracks appear at the surface of SiO2 after electron beam irradiation, owing to the thermal effect, and that the crack density and size increase with increasing radiation dose. The morphology of the surface cracks is analyzed by using atomic force microscope and the width of crack is about 1 μm. In addition, there are a large number of debris particles with sizes of 0.1–1 μm on the surface. From the optical absorption spectrum of each of all samples, a weak absorption peak at 394 nm is observed and the absorbance increases at the beginning then decreases with increasing electron-radiation dose. Before and after irradiation, three absorption bands at 460 nm, 496 nm and 520 nm are clearly observed and their intensities first increase and then decrease, which is consistent with the results of absorption spectra. The effect of electron dose on the laser induced damage threshold (LIDT) at 355 nm is investigated and the results indicate that the LIDT decreases with increasing dose. At the lower electron doses, the color centers are responsible for the decrease of LIDT. However, at the higher electron doses, the decrease of LIDT is due to the light modulation and absorption induced by microscale cracks and debris particles at the surface of irradiated fused silica.
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