基于空间整形飞秒激光脉冲的纳米线可控制备

相对于块体材料，金属纳米线由于其独特的机械、电学和光学性能，在近几十年来受到了广泛的关注。这种一维纳米结构制备技术的发展极大地促进了各种小型化器件的发展，包括电化学传感器、柔性电极、表面增强拉曼散射（SERS）衬底和等离子体波导。然而，这些技术的广泛应用仍然面临着挑战，即在这些器件的选定区域、在大气环境条件下稳定和有效地制备纳米线。

超快激光直写技术具备在各种材料上实现精确和可重复的微/纳米结构的能力，并对加工条件的敏感性很小。在纳米结构制造中，高数值孔径物镜通常被用于提高分辨率，但实现超越衍射极限的加工仍然是一个问题。因此，设计一种激光微纳直写加工技术来实现对金属纳米线尺寸形状的灵活调控，将会大大拓展飞秒激光制备微纳结构的自由度，同时对激光微纳制造的应用研究也具有至关重要的促进作用。

本论文提出了一种新的远场激光直写加工方法，利用具有双峰强度分布的整形矢量光束制备远超衍射极限的纳米线阵列。空间整形后的飞秒激光光束通过选择性烧蚀来制备纳米线，通过调整相对于激光扫描方向的双峰光斑方向辅助以多道次扫描策略可大大减小纳米线的线宽。利用低数值孔径物镜（NA = 0.1），在远场制备了宽度为157 nm（小于λ/3，约1/20的衍射极限）的金纳米线。利用多焦点分束光束进行并行加工，大大提高了纳米线的加工效率。此外，我们测试了纳米线的电学性能，并由此设计制备了基于纳米线阵列的应变传感器。该应变传感器具有良好的线性度和机械耐久性，在低应变（<0.6%）下的应变因子GF≈13.6，能够在日常生活中对监测人体细微动作提供有效帮助。

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