Plasmonic high-harmonic generation (HHG) drew attention as a means of producing coherent extreme ultraviolet (EUV) radiation by taking advantage of field enhancement occurring in metallic nanostructures. Here a metal-sapphire nanostructure is devised to provide a solid tip as the HHG emitter, replacing commonly used gaseous atoms. The fabricated solid tip is made of monocrystalline sapphire surrounded by a gold thin-film layer, and intended to produce EUV harmonics by the inter- and intra-band oscillations of electrons driven by the incident laser. The metal-sapphire nanostructure enhances the incident laser field by means of surface plasmon polaritons, triggering HHG directly from moderate femtosecond pulses of ∼0.1 TW cm−2 intensities. The measured EUV spectra exhibit odd-order harmonics up to ∼60 nm wavelengths without the plasma atomic lines typically seen when using gaseous atoms as the HHG emitter. This experimental outcome confirms that the plasmonic HHG approach is a promising way to realize coherent EUV sources for nano-scale near-field applications in spectroscopy, microscopy, lithography and atto-second physics.
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机译:等离子体高谐波产生(HHG)作为利用金属纳米结构中发生的场增强的优势产生相干极紫外(EUV)辐射的一种方法引起了人们的注意。在这里,设计了一种金属-蓝宝石纳米结构,以提供固体尖端作为HHG发射体,从而替代了常用的气态原子。制成的实心尖端由被金薄膜层包围的单晶蓝宝石制成,旨在通过入射激光驱动的电子的带内和带内振荡产生EUV谐波。金属-蓝宝石纳米结构通过表面等离激元极化子增强入射激光场,直接从强度约为0.1 TW cm -2 sup>的飞秒脉冲触发HHG。使用气态原子作为HHG发射体时,测得的EUV光谱显示出高达60 nm波长的奇数阶谐波,而没有看到等离子原子线。该实验结果证实,等离激元HHG方法是实现相干EUV光源的有前途的方法,可用于光谱学,显微镜,光刻和亚秒物理学的纳米级近场应用。
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