德国基尔大学
研究人员提出了一种基于阴极发光光谱在电子显微镜中引入内部辐射的逆向方法。这种紧凑方法是基于电子束与电子驱动的光子源和被研究样品的顺序相互作用。在电子显微镜下，这种源产生的锁相光子与快速电子的近场分布互相干。研究人员确认了电子驱动的光子源和样品辐射的相互频率和动量依赖相关性，并确定了高达27%的互相干度。有了这种水平的相干度，研究小组能够利用电子显微镜进行光谱干涉测量。相比于传统的超快光子-电子光谱方法，该方法简单、紧凑，且使用连续电子束，将为量子材料、单光子系统和具有纳米分辨率的相干激子-极化子样品的局部光子-电子相干谱研究提供新的思路。
据悉，电子显微镜中的超快光子-电子光谱通常需要超快激光装置。通过利用工程电子源的光电发射来产生脉冲电子，使其在已知时间延迟下与激光脉冲激发的样品相互作用。因此，开发超快电子显微镜需要利用外部激光激发和复杂的同步方案。
附：英文原文
Title: Phase-locked photon–electron interaction without a laser
Author: Taleb, Masoud, Hentschel, Mario, Rossnagel, Kai, Giessen, Harald, Talebi, Nahid
Issue&Volume: 2023-02-23
Abstract: Ultrafast photon–electron spectroscopy in electron microscopes commonly requires ultrafast laser setups. Photoemission from an engineered electron source is used to generate pulsed electrons, interacting with a sample excited by the laser pulse at a known time delay. Thus, developing an ultrafast electron microscope demands the exploitation of extrinsic laser excitations and complex synchronization schemes. Here we present an inverse approach to introduce internal radiation sources in an electron microscope based on cathodoluminescence spectroscopy. Our compact method is based on a sequential interaction of the electron beam with an electron-driven photon source and the investigated sample. Such a source in an electron microscope generates phase-locked photons that are mutually coherent with the near-field distribution of the swift electron. We confirm the mutual frequency and momentum-dependent correlation of the electron-driven photon source and sample radiation and determine a degree of mutual coherence of up to 27%. With this level of mutual coherence, we were able to perform spectral interferometry with an electron microscope. Our method has the advantage of being simple, compact and operating with continuous electron beams. It will open the door to local photon–electron correlation spectroscopy of quantum materials, single-photon systems and coherent exciton–polaritonic samples with nanometre resolution.
DOI: 10.1038/s41567-023-01954-3
Source: https://www.nature.com/articles/s41567-023-01954-3