ULTRAFAST ALL-OPTICAL SPATIO-TEMPORAL ELECTRON MODULATORS: OPENING NEW FRONTIERS IN ELECTRON MICROSCOPY

Project Information

SMART-electron

Grant agreement ID: 964591

DOI

10.3030/964591

Project closed

EC signature date 21 December 2020

Start date 1 May 2021

End date 30 April 2025

Funded under

• EXCELLENT SCIENCE - Future and Emerging Technologies (FET)

Total cost

€ 3 042 910,00

EU contribution

€ 3 042 910,00

Coordinated by

UNIVERSITA' DEGLI STUDI DI MILANO-BICOCCA
Italy

Periodic Reporting for period 3 - SMART-electron (ULTRAFAST ALL-OPTICAL SPATIO-TEMPORAL ELECTRON MODULATORS: OPENING NEW FRONTIERS IN ELECTRON MICROSCOPY)

Reporting period: 2023-11-01 to 2025-04-30

Summary of the context and overall objectives of the project

The vision behind the SMART-electron project has been the development of unconventional imaging methods based on light-modulated electrons for unprecedented visualization of matter, which is key for addressing grand-challenges that the world is facing nowadays, in terms of ‘energy’, ‘information’ and ‘health’.

During the first phase of the project, we have moved beyond past schemes of static modulation of an electron beam developing an all-optical rapidly-programmable phase mask for electrons. Properly-shaped ultrafast light fields have been used for engineering the phase space of an electron wave function prior to its interaction with the sample, achieving unprecedented space/time/energy/momentum shaping. This demonstrates the main technological innovation of the project: a Photonic ELectron Modulator (PELM) for light-mediated dynamic/versatile electron beam shaping, which can be easily retrofitted in any TEM.

During the second phase of the project, we have then used such unique tool to develop novel imaging approaches in electron microscopy with enhanced features. In particular, we have implemented three new beyond-the-state-of-the-art electron imaging methods, namely: Ramsey Holographic Imaging (RHI), Electron Single Pixel Imaging (ESPI), and Enhanced Electron Imaging Contrast (EEIC).

During the third phase of the project, we have then employed the three novel methods enabled by our PELM modulator to achieve unprecedented visualization of: i) low-energy excitations in quantum materials, ii) dynamic evolution of electrochemically-active materials, and iii) enhanced spatial localization of biocompatible nanoparticles for drug delivery applications.

On a general level, the enhanced imaging capabilities that we have developed within the SMART-electron project - thus successfully realizing our initial vision - represent a game changer in our ability to investigate the dynamic behavior of materials, playing a decisive role in our ability to respond to the global demands for: i) efficient energy storage, ii) innovative quantum computing schemes, and iii) effective cancer treatments and tumour targeting.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

1) Theoretical modelling and full experimental characterization of an all-optical electron modulator
We have demonstrated full phase-space characterization of light-induced modification of the electron phase and amplitude profiles in space (nm), time (sub-fs), energy (sub-eV) and momentum (μm^-1). We have performed measurements of light-induced transverse and longitudinal electron shaping with a Spatial Light Modulator. In parallel we have performed design, optical characterization, and nanofabrication of a focusing metalens to be inserted in the PELM.

2) Design, realization, installation, operation and characterization of Photonic free-ELectron Modulator (PELM) devices at EPFL, TECHNION and UNIMIB.
We have worked at the design, prototype realization, mechanical installation, operation, commissioning and characterization of the PELM devices in the UTEM at TECHNION, EPFL and UNIMIB. We have successfully operated 3 photonics electron modulators (at the pre-CL stage, at the sample-stage, and at the post-CL stage). Finally, we have designed further upgrades to the PELM devices and performed a full performance optimization analysis.

3) Implementation of the Ramsey Holographic Imaging (RHI) method
We have developed RHI by using phase-modulated free-electron pulses in a homodyne detection scheme. We have demonstrated simultaneous phase-resolved dynamics of near-field in test nanostructures, which is not possible using current approaches. Finally, we have applied our method to the investigation of quantum materials, and specifically to the phase dynamics of Berry singularities in 2D hexagonal boron nitride, as well as to the coherent control of Skyrmions lattice in multiferroic Cu2OSeO3.

4) Implementation of the Electron Single Pixel Imaging (ESPI) method
We have performed ESPI reconstruction using optically-modulated electron pulses on several type of samples in a 4D-STEM mode where the SLM-shaped light is used in conjunction with a momentum-resolved analysis. We have tested our method on several nanofabricated structures as well as MAX phase nanoparticles on a lateral scale of 1-10 μm and sub-ps time scale. Finally, we have performed ultrafast structural analysis of MAX nanoparticles in a pump-probe scheme with transversely-modulated electrons for improving the beam lateral coherence.

5) Implementation of the Quantum Cathodoluminescence (Q-CL) and Enhanced Electron Imaging Contrast (EEIC) methods
We have designed, realized, and operated a modified TEM sample holder for measuring coherent and incoherent light emission from quantum emitters. However, we have not been able to observe a level of coherent light emission needed to demonstrate superradiance. Nevertheless, we developed a contingency plan thanks to which we demonstrated Enhanced Electron Imaging Contrast of nanostructures via photon-mediated or plasma-mediated interactions with enhancement factors ranging from 50 to 800 %. We have then performed experiments on lipo-gold nanoparticles and on HeLa cells incubated with lipo-gold nanoparticles, showing enhanced contrast of 30 – 40 % with simultaneous μm-spatial and sub-ps temporal resolutions.

6) Dissemination & communication
We have also focused on the outreach strategies via social media presence and engagement events. We have organized: 3 international conferences, 13 workshop/seminars, 5 outreach events, 5 science bashes. The partners have attended > 80 international events and published over 40 papers.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

- Progress beyond the state of the art
From a scientific point of view, we have demonstrated a new optical method in electron microscopy that enables modulation of electron beams via inelastic interaction with computer-controlled arbitrary light fields. This represents a radical change of paradigm in the field of electron manipulation, where fast, tailored, and versatile modulation can now be achieved. Key to our new approach is such level of arbitrary dynamic shaping, which was missing in previous works.
From a technological point of view, we have developed, realized and operated successfully three prototypes of photonics-based electron modulators. The deployment of such device is the legacy of the SMART-electron project.
From an application point of view, we have adopted such electron modulators to implement for the first time Ramsey Holographic Imaging, Electron Single Pixel Imaging, and Enhanced Contrast Imaging applied to quantum materials, electrochemical materials and biomaterials, respectively.

- Socio-economic impact and wider societal implication
Directly connected to the breakthrough fostered by SMART-electron, the project has prompted generation of intellectual property and patents. As a result, a novel device would potentially be available to several end users, such as other research groups and/or research institutions and SMEs in the field of photonics and electron microscopy. These scientific and technological advancements are significantly contributing to strengthening European leadership in the these fields. At the same time, the project is providing paid work to a number of excellent young researchers. Gender balance has been pursued and the whole Consortium has been committed to support young female researchers. In addition, several dissemination actions for participatory shared knowledge have been pursued.

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