Bulk damage and absorption in fused silica due to high-power laser applications
Bulk damage and absorption in fused silica due to high-power laser applications
复制标题
高功率激光应用导致熔融石英的体损伤和吸收
DOI：
10.1117/12.2194289
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发表时间：
2015
影响因子：
38.3
通讯作者：
J. Vydra
中科院分区：
文献类型：
--
作者：
F. Nürnberg;B. Kühn;A. Langner;M. Altwein;G. Schötz;R. Takke;S. Thomas;J. Vydra
激光聚变项目正朝着红外光学的方向发展，这些光学具有高宽带传输、高抗冲击性和耐温性、长激光寿命和最佳纯度。对于这种应用，熔融石英是一个很好的选择。红外激光光学系统的能量密度阈值主要受熔石英的纯度和均匀性的影响。研究了各种合成熔融石英等级的羟基含量的吸收行为。OH的振动激发对石英玻璃的主吸收产生影响，导致富OH和低OH石英玻璃的红外衰减不同。工业激光系统旨在尽可能地提取最大能量。贺利氏石英光纤开发了一种掺镱熔融石英光纤，以支持这一不断增长的市场。但是激光焊接和切割系统的性能从根本上受到光束质量和焦点稳定性的限制。由于光学系统的光学部件中的吸收对激光焦点偏移具有不利影响，因此必须在体材料和涂覆表面两者中最小化光束能量损失和由此产生的加热。与激光研究所、光学精加工商和最终用户合作，对不同等级的熔融石英涂层样品进行光热吸收测量，以研究基本材料特性对吸收水平的影响。高纯度合成熔融石英也是为深紫外应用（波长范围160 nm - 260 nm）设计的光学元件的首选材料。对于例如由准分子激光器提供的较高光强度，UV光子可能产生在使用期间影响光学性质的缺陷中心，从而导致光学部件的老化（UV辐射损伤）。强大的准分子激光器需要能够承受接近带隙的光子能量和短脉冲长度的高强度的光学材料。UV透射损失被限制在低于300 nm的DUV波长范围内，并且由三个不同的吸收带组成，这些吸收带以165 nm（过氧自由基）、215 nm（E '-中心）和265 nm（非桥接氧空穴中心（NBOH））为中心，这改变了材料的透射行为。
Laser fusion projects are heading for IR optics with high broadband transmission, high shock and temperature resistance, long laser durability, and best purity. For this application, fused silica is an excellent choice. The energy density threshold on IR laser optics is mainly influenced by the purity and homogeneity of the fused silica. The absorption behavior regarding the hydroxyl content was studied for various synthetic fused silica grades. The main absorption influenced by OH vibrational excitation leads to different IR attenuations for OH-rich and low-OH fused silica. Industrial laser systems aim for the maximum energy extraction possible. Heraeus Quarzglas developed an Yb-doped fused silica fiber to support this growing market. But the performance of laser welding and cutting systems is fundamentally limited by beam quality and stability of focus. Since absorption in the optical components of optical systems has a detrimental effect on the laser focus shift, the beam energy loss and the resulting heating has to be minimized both in the bulk materials and at the coated surfaces. In collaboration with a laser research institute, an optical finisher and end users, photo thermal absorption measurements on coated samples of different fused silica grades were performed to investigate the influence of basic material properties on the absorption level. High purity, synthetic fused silica is as well the material of choice for optical components designed for DUV applications (wavelength range 160 nm - 260 nm). For higher light intensities, e.g. provided by Excimer lasers, UV photons may generate defect centers that effect the optical properties during usage, resulting in an aging of the optical components (UV radiation damage). Powerful Excimer lasers require optical materials that can withstand photon energy close to the band gap and the high intensity of the short pulse length. The UV transmission loss is restricted to the DUV wavelength range below 300 nm and consists of three different absorption bands centered at 165 nm (peroxy radicals), 215 nm (E’-center), and 265 nm (non-bridging oxygen hole center (NBOH)), which change the transmission behavior of material.