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CORDIS - EU research results



Reporting period: 2022-05-01 to 2023-10-31

Addressing the grand-challenges that the world is facing nowadays regarding ‘energy’, ‘information’ and ‘health’ requires the development of unconventional methods for unprecedented visualization of matter. To make this a reality, we are departing from current schemes, which rely on passive and static modulation of an electron wave function using monolithic phase masks or slowly-varying electrostatic and magnetostatic displays. In SMART-electron we are developing an innovative technological platform for designing, realizing and operating all-optical rapidly-programmable phase masks for electrons. By introducing a new paradigm where properly synthesized ultrafast optical fields are used for engineering the phase space of a free-electron wave function, we are able to achieve unprecedented space/time/energy/momentum shaping of electron matter waves.

Such unique high-speed, flexible and precise control, is enabling the development of novel advanced imaging approaches in electron microscopy with enhanced features, revolutionizing the way materials are investigated. In particular, we are implementing three beyond-the-state-of-the-art imaging techniques enabled by our photonic electron modulator, namely: (1) Ramsey-type Holography, (2) Electron Single-Pixel Imaging, and (3) Quantum Cathodoluminescence. Such new approaches will lead to unprecedented visualization of many-body states in quantum materials, real-time electrochemical reactions, and spatio-temporal localization of nanoparticles in cells for drug delivery.
On a general level, such enhanced imaging capabilities will be a game changer in our ability to visualize the dynamic behavior of nanoscale materials and control the interplay of their multiple degrees of freedom, providing a direct handle on their electronic, optical and thermal properties. This aspect will have a strong technological impact in designing and implementing new-generation devices with unprecedented performance. This will play a decisive role in our ability to respond to the global demands of: i) efficient energy storage; ii) innovative quantum computing schemes; and iii) effective cancer treatments and tumour targeting.
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). In parallel, we are developing an artificial neural network for real time optimization of the modulation pattern.

3) Implementation of the Ramsey Holographic Imaging (RHI) method for a test sample.
We have developed RHI by using phase-modulated free-electron pulses in a homodyne detection scheme. By adopting both the sample-stage PELM at EPFL and the post-CL PELM at TECHNION, we have demonstrated simultaneous phase-resolved dynamics and coherent amplification of the measured signal, which are not possible using current approaches.

4) Implementation of the Electron Single Pixel Imaging (ESPI) method for a test sample.
First, we have integrated and characterized a direct detector and a RF cavity in the UTEM at UNIMIB. By adopting the pre-CL PELM at UNIMIB, we have performed SPI reconstruction of a MAX phase nanostructure on a sub-ps time scale by means of transversely-modulated electron pulses via SLM-controlled fs light pulses.

5) Implementation of the Quantum Cathodoluminescence (Q-CL) method for test sample.
First, we have designed, realized, installed and characterized a modified TEM sample holder for efficient light collection. Then, we started the work on Q-CL from both a theoretical and an experimental points of view. By adopting the post-CL stage PELM, our aim is to demonstrate coherently enhanced light emission from quantum emitters when interrogated using longitudinally-modulated electron pulses.

6) Dissemination & communication
We have also focused on the outreach strategy, defining the SMART-electron visual identity, the online presence, D&C materials, citizen science engagement events, and the organization of two SMART-electron international conferences.
- 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. These studies represent 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, together with its continuous development, would lead to further implementations that go beyond the lifetime of the project.
From an application point of view, we have adopted such electron modulators to implement for the first time Ramsey Holographic Imaging and light-induced ultrafast Single Pixel Imaging for test cases. A the moment we are still working to demonstrate the Quantum Cathodoluminescence method.

- Expected results until the end of the project
The final strategic objective is the ability to radically change how materials are investigated in electron microscopy. In particular, we will pursue the following target applications for each imaging modality:
1) Investigation of the dynamics of low-energy excitations in quantum materials via Ramsey-Holography.
2) Real-time mapping of electrochemical reactions via ultrafast Electron Single Pixel Imaging.
3) Superradiant spatio-temporal localization of nanoparticles in cells (for drug delivery) via Quantum Cathodoluminescence.

- Socio-economic impact and wider societal implication
Directly connected to the breakthrough fostered by SMART-electron, the project will prompt the 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. The scientific and technological advancements described above 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 is being pursued and the whole Consortium is committed to support young female researchers. In addition, several dissemination actions for participatory shared knowledge are being pursued.
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