CO_(2)激光改性溶胶-凝胶SiO_(2)薄膜光谱及紫外纳秒激光损伤特性研究

Study on the Spectral and Laser Damage Resistance of CO_(2) Laser Modified Sol-Gel SiO_(2) Thin Films

研究了经过CO_(2)激光处理的溶胶-凝胶SiO_(2)薄膜的物理化学性能和抗激光损伤性能,研究结果表明激光处理后薄膜表面变得更加光滑,粗糙度从14.08 nm降低到9.76 nm,下降了30%以上;薄膜的厚度随着CO_(2)激光处理功率增加有所降低,经过20 W激光处理后薄膜的厚度下降了17%~28%,而薄膜的弹性模量和硬度等力学性能获得提升,弹性模量从1.5 GPa增加到6 GPa,硬度从40 MPa增加到110 MPa;傅里叶变换红外光谱测试结果表明激光处理后薄膜的傅里叶光谱峰值从1 125 cm^(-1)移动至1 120 cm^(-1),薄膜中的硅原子和氧原子的平均桥键角变小,原因为CO_(2)激光处理时会使局部温度升高,会加速Si—OH键脱水缩合,孔隙率降低,吸收下降。采用紫外纳秒激光对薄膜进行损伤测试,结果显示经过12 W CO_(2)激光处理后的薄膜与未经过CO_(2)激光处理的薄膜相比损伤面积更小,而损伤阈值从4.8 J·cm^(-2)上升到7 J·cm^(-2),提升了46%;经过16 W和20 W CO_(2)激光处理的薄膜紫外纳秒激光损伤阈值没有明显变化,原因为较高功率CO_(2)激光处理导致薄膜表面发生烧蚀沉积,沉积物会影响紫外纳秒损伤阈值无法有效改善薄膜的激光损伤性能。研究结果表明CO_(2)激光处理技术可以有效改善溶胶-凝胶SiO_(2)薄膜的弹性模量、硬度等力学性能和抗激光损伤性能,CO_(2)激光的功率对薄膜性能影响较大,CO_(2)激光处理是一种有效的提升溶胶-凝胶SiO_(2)薄膜紫外纳秒激光损伤特性的技术手段。

This paper studied the physicochemical properties and laser damage resistance of sol-gel thin films conditioned with CO_(2) laser.The results show that the surface roughness of the thin film after laser conditioning decreased from 14.08 to 9.76 nm,with a decrease of more than 30%.The thickness of the film decreases with the increase of the laser power.After laser conditioning of 20 W,the thickness of the film decreases by about 17%~28%.The mechanical properties,such as elasticity modulus and hardness,were improved after laser conditioning.The elasticity modulus increased from 1.5 to 6 GPa,and the hardness increased from 40 to 110 MPa.Results of Fourier transform infrared spectroscopy show that after laser conditioning,the main peak shifted from 1125 to 1120 cm^(-1),and the average bridge bond angle between silicon and oxygen atoms became small.The reason is that during the CO_(2) laser conditioning,the local temperature increase which accelerates the dehydration and condensation of Si—OH bond,and reduce the porosity and absorption.UV nanosecond laser was applied to the laser damage test of the film,and the results show that the laser damage area of the film after 12 W laser conditioning is smaller than the film without laser conditioning,and the laser damage threshold is increased from 4.8 to 7 J·cm^(-2),which increased by 46%;However,the laser damage threshold after 16 and 20 W laser conditioning did not changes significantly,that is due to the ablation deposition occurred on the film’s surface after high-power laser conditioning,which will affect the UV nanosecond laser damage threshold and can not effectively improve the laser damage resistance.The results of this study show that CO_(2) laser conditioning can effectively improve the mechanical properties,including elasticity modulus,hardness of sol-gel SiO_(2) films and the laser damage resistance.CO_(2) laser’s power has a great impact on the properties of the films.CO_(2) laser conditioning is an effective technical means to improve the UV nanosecond laser damage resistance of sol-gel SiO_(2) films.