近日，德国康斯坦茨大学的Peter Baum和Andrey Ryabov课题组取得一项新进展。经过不懈努力，他们成功地研发了一种能够在亚周期时间尺度下实现光学动力学观测的阿秒电子显微镜。相关研究成果已于2023年5月31日在国际权威学术期刊《自然》上。

该研究团队成功将透射电子显微镜技术推进到亚秒级时间分辨率，实现对光激发周期内光学响应的观察。为了达到这一目标，研究人员利用连续波激光来调制电子波函数，形成快速序列的电子脉冲，并使用能量过滤器在空间和时间上解析材料内外的电磁近场，形成了一部"电影"。通过在纳米结构的针尖、介质共振器和超材料天线上进行实验，他们揭示了手性表面波的定向发射、偶极和四极动力学之间的延迟、亚光速的掩埋波导场以及对称性破缺的多天线响应。这些发现表明，结合电子显微镜和阿秒激光科学，从时空的基本维度上理解光与物质相互作用具有重要意义。

据悉，理解和控制材料的电磁响应对于现代光学和纳米光子学至关重要，因为几乎所有光与材料相互作用的关键步骤是电子对入射光波的光周期尺度和亚周期尺度下的电动力响应。虽然电子束具有极小的德布罗意波长，可以实现亚秒和埃尺度的测量，但迄今为止，超快电子显微镜和衍射技术的时间分辨率仅限于飞秒级，无法记录光周期尺度上的基本材料响应。

附：英文原文

Title: Attosecond electron microscopy of sub-cycle optical dynamics

Author: Nabben, David, Kuttruff, Joel, Stolz, Levin, Ryabov, Andrey, Baum, Peter

Issue&Volume: 2023-05-31

Abstract: The primary step of almost any interaction between light and materials is the electrodynamic response of the electrons to the optical cycles of the impinging light wave on sub-wavelength and sub-cycle dimensions. Understanding and controlling the electromagnetic responses of a material is therefore essential for modern optics and nanophotonics. Although the small de Broglie wavelength of electron beams should allow access to attosecond and ångström dimensions, the time resolution of ultrafast electron microscopy and diffraction has so far been limited to the femtosecond domain, which is insufficient for recording fundamental material responses on the scale of the cycles of light. Here we advance transmission electron microscopy to attosecond time resolution of optical responses within one cycle of excitation light. We apply a continuous-wave laser to modulate the electron wave function into a rapid sequence of electron pulses, and use an energy filter to resolve electromagnetic near-fields in and around a material as a movie in space and time. Experiments on nanostructured needle tips, dielectric resonators and metamaterial antennas reveal a directional launch of chiral surface waves, a delay between dipole and quadrupole dynamics, a subluminal buried waveguide field and a symmetry-broken multi-antenna response. These results signify the value of combining electron microscopy and attosecond laser science to understand light–matter interactions in terms of their fundamental dimensions in space and time.

DOI: 10.1038/s41586-023-06074-9

Source: https://www.nature.com/articles/s41586-023-06074-9