355nm脉冲激光清洗溶胶-凝胶膜面颗粒污染

Particulate contaminants removal on sol-gel film using 355 nm pulsed-laser

在强激光系统中,光学元件表面的颗粒污染极大地限制了元件的使用寿命.本文在355 nm纳秒脉冲激光入射下,采用激光等离子体冲击波光栅式扫描技术,清洗了溶胶-凝胶Si O2薄膜表面的石英颗粒污染.当瞄准距d取为0.5~1.5 mm时,膜面的清洗效率η达到90%以上.当d〈0.5 mm时,膜面易产生等离子体灼伤.当d接近3 mm时,清洗效果基本丧失.采用紫外-可见分光光度计、静滴接触角测量仪与原子力显微镜对样品进行测试.结果表明,冲击波清洗之后,元件透射峰能恢复到污染前的状态.由于冲击波对颗粒的碎裂作用,清洗后膜面均方根粗糙度由1.755 nm增大为2.681 nm,膜面与水的接触角由48°减为6°,其抗污染能力明显变差.

In the high power laser systems,particle contamination on the optical devices substantially limits its lifetime.A 355 nm nanosecond pulsed laser is utilized to induce optical break down of the air above the sol-gel SiO_2 coating and the created Shockwave removes the quartz particles.The laser cleaning efficiency η is above 90%when the gap distance d ranges from 0.5 to 1.5 mm.As d 0.5 mm,the film is scalded by the plasma.When d is extended to 3 mm,the cleaning effect disappears.The samples have been characterized by UV-vis spectroscopy,contact angle measuring device and atomic force microscopy.Results show that the transmission peak returns to the as-deposited samples after the laser cleaning.Surface roughness increases from 1.755 to 2.681 nm.The contact angle of the film with water reduces from 48° to 6°,indicating that its anti-pollution performance deteriorates.They are due to the large particles broken into small pieces under plasma Shockwave.