A critical component for all high-power laser systems that is particularly susceptible to laser damage is the antireflective coating, which maximizes energy transmission and minimizes scattered and stray light. We demonstrate the ability to generate substrate-engraved nanostructured surfaces (NS) for scalable and designable antireflective (AR) coatings that are monolithic to the substrate and can handle peak power levels comparable to the bulk material. Experimentally measured reflectance from these fabricated structures has validated our effective index theory-based transmission matrix model, demonstrating the designability of the AR properties. Upon exposure to sufficiently high fluences, a new mode of damage, nanostructured surface damage, has been observed and is likely the result of thermally driven material reflow accompanied by plasma initiation on the nanostructured surface. At 1053 nm, nanostructured surface damage onsets at ${39}\;{{\rm J/cm}^2}$ with sample cleaning and ${74}\;{{\rm J/cm}^2}$ after laser conditioning—very close to the reference substrate at ${81}\;{{\rm J/cm}^2}$. At 351 nm we show damage onset of ${30}\;{{\rm J/cm}^2}$, with reference substrate material damage onset of ${47}\;{{\rm J/cm}^2}$. Therefore, damage is close to the bulk material and represents an improvement with respect to other methods. The nanostructured surfaces were found to be mechanically durable and able to withstand cleaning procedures with sonication. Under normal incidence mechanical testing with a 200 µm radius indenter tip, the AR performance of these nanostructured surfaces was minimally impacted at pressures orders of magnitude higher than an average fingerprint pressure—indicating that incidental handling contact will not affect NS structures. Mechanical damage is attributed to plastic compression, not fracturing of the NS features. We demonstrate for the first time, to the best of our knowledge, that NS AR coatings, despite being rich in etched surface features, can tolerate laser fluences comparable to unprocessed optical surfaces. Furthermore, laser-damage features of NS indicate a unique non-growing failure mode whereby following absorption the featureless damage site does not precipitate future damage growth, reducing considerably the burdens for managing optics processing in high-power laser systems.

中文翻译：

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用于大功率激光应用的刻有基材的抗反射纳米结构表面

对于所有大功率激光系统而言，特别容易受到激光损坏的关键组件是抗反射涂层，该涂层可使能量传输最大化，并使散射光和杂散光最小化。我们展示了生成可雕刻且可设计的抗反射（AR）涂层的基板雕刻纳米结构表面（NS）的能力，该涂层对基板是整体的，并且可以处理与散装材料相当的峰值功率。从这些制造的结构进行实验测量的反射率已验证了我们基于有效折射率理论的透射矩阵模型，证明了AR性能的可设计性。暴露于足够高的通量后，会出现一种新的损伤模式，即纳米结构表面损伤，已经观察到并且很可能是热驱动材料回流伴随纳米结构表面上的等离子体引发的结果。在1053 nm处，纳米结构表面损伤开始于$ {39} \; {{\ rm J / cm} ^ 2} $（带样品清洁）和$ {74} \; {{\ rm J / cm} ^ 2} $（激光调节后），非常靠近参考基板在$ {81} \; {{\ rm J / cm} ^ 2} $中。在351 nm处，我们显示损伤开始为$ {30} \; {{\ rm J / cm} ^ 2} $，参考基板材料损伤开始为$ {47} \ ;; {{\ rm J / cm} ^ 2 } $。因此，损坏接近于散装材料，并且表示相对于其他方法的改进。发现纳米结构表面在机械上是耐用的，并且能够经受超声处理的清洁程序。在具有200 µm半径压头的法向入射机械测试中，这些纳米结构表面的AR性能在比平均指纹压力高几个数量级的压力下受到的影响最小，这表明偶然的处理接触不会影响NS结构。机械损伤归因于塑性压缩，而不是NS部件的断裂。据我们所知，这是我们首次证明，尽管NS AR涂层具有丰富的蚀刻表面特征，但其耐激光通量与未加工的光学表面相当。此外，