Ultrafast lensless imaging with plasmonic enhanced XUV generation

IPEX项目建议研究由等离子体共振辅助的MHz重复率激光器产生的极紫外相干光，以实现电场的局部增强。2008年，Kim等人使用蝴蝶结纳米天线以75 MHz的重复率产生高谐波（HH）辐射[Kim等人，Nature 2008]。最近，Ropers（Sivis et al.，Nature 2012），使用与Kim等人几乎相同的条件，观察到了暴露于气体的纳米结构的XUV发射，但得出了不同的结论。他们将XUV辐射归因于中性和电离原子的非相干发射线。IPEX项目将通过检查这种基于纳米结构的XUV源的相干特性来解决这一争议。我们将使用该源进行涉及超快相干衍射成像的第一次实验。我们将从2D开始，继续3D静态测试对象，以研究材料中的超快纳米级运动。此外，我们将其特点的超短时间结构的谐波发射，并利用它作为一个探针阿秒等离子体动力学利用自探测原子钟技术。该方法将依赖于新的纳米结构，强场物理学和最先进的超快激光振荡器。请注意，该项目只有通过结合两个合作伙伴CEA（法国）和IO汉诺威（德国）的互补专业知识才能实现。一方面，IO汉诺威拥有一个新的实验室设施，通过纳米等离子体场增强研究HH生成（HHG），并获得了同行评议的有希望的结果。另一方面，CEA已经展示了相干衍射成像和磁散射技术，在单次拍摄和亚100 nm的空间分辨率使用强HHG源。由于重复频率在Mhz范围内，XUV范围内的潜在高亮度和超短脉冲持续时间，等离子体HH源为大型设施（如同步加速器，FEL或太瓦激光驱动的XUV源）提供了独特且廉价的替代方案。

The IPEX project proposes to study the extreme ultraviolet (XUV) coherent light generation from MHz repetition-rate lasers assisted by plasmonic resonances to achieve local enhancements of electric fields. In 2008, Kim et al. used bowtie nano-antennae to produce high-harmonic (HH) radiation at a repetition rate of 75 MHz [Kim et al. Nature 2008]. Recently, the group of Ropers (Sivis et al., Nature 2012), using nearly identical conditions as Kim et al., observed XUV emission from the gas-exposed nanostructures, but came to a different conclusion. They attributed the XUV radiation to incoherent emission lines of neutral and ionized atoms.The IPEX project will contribute to resolve this controversy by examining the coherence properties of such a nanostructure-based XUV source. We will use the source to perform first experiments involving ultrafast coherent diffractive imaging. We will start with 2D and continue with 3D static test objects to study ultrafast nanoscale motions in materials. Furthermore, we will characterize the ultrashort time structure of the harmonic emission and exploit it as a probe for attosecond plasmonic dynamics utilizing a self-probing atomic clock technique. The methodology will rely on novel nano-structures, strong field physics, and state-of the art ultrafast laser oscillators.Note that this project is only possible by combining the complementary expertise of the two partners CEA (France) and IO Hannover (Germany). On one hand, IO Hannover has a new lab facility to investigate HH generation (HHG) through nanoplasmonic field enhancement with peer-reviewed promising results. On the other hand, CEA has demonstrated coherent diffractive imaging and magnetic scattering technique in single shot and with sub-100 nm spatial resolution using an intense HHG source. With a repetition rate in the Mhz range, a potentially high brilliance in the XUV regime, and ultrashort pulse duration, plasmonic HH sources present a unique and inexpensive alternative to large-scale facilities such as synchrotrons, FELs, or terawatt laser-driven XUV sources.