Attosecond Electron Microscopy: imaging the electron motion in action

Wednesday, May 24, 2023 - 3:00pm

SpeakerMohammed Hassan, University of Arizona

Program Description:

Ultrafast Electron Diffraction and Microscopy imaging have been demonstrated to be pivot tools for imaging the atomic motion in real-time and space 1-3. The generation of a few hundred femtoseconds electron pulses enabled recording movies for molecular and atomic motion4. However, the technical challenges in electron pulse compression have limited the temporal resolution of electron imaging experiments to a hundred femtoseconds. Here, we demonstrate the attosecond temporal resolution in the transmission electron microscope by optical gating 5 to establish what we so-called “Attomicroscopy” 6. Moreover, we utilized the Attomicroscopy to image the electron motion dynamics in graphene. In a strong field, the electron is moving in the reciprocal space following the waveform of the driver field. The attosecond electron diffraction experiment allowed us to study the electron density distribution in the reciprocal space at different time instants and connect it with the electron motion in real space. The demonstrated Attomicroscopy imaging tool opens the avenue to study electron motion in neutral matter and promises new electron imaging applications in physics, chemistry, and biochemistry 6.

The electron imaging allows to control the electron motion in real time and space. In the second part of my talk I will present our developed light field synthesizer device which we used for on-demand tailoring of light field waveforms 7. We utilized complex synthesized waveforms to demonstrate the quantum electron motion control in dielectric systems 8. This fine control allowed for switching the optical signal (ON/OFF) with sub-femtosecond time resolution9. Furthermore, we demonstrated the encoding of binary data on ultrashort light waveforms. This technology can be implemented on a chip paving the way for establishing optical switches and light-based electronics with petahertz speeds, several orders of magnitude faster than the current semiconductor-based electronics, opening a new realm in information technology, optical communications, and photonic processors technologies.


[1]   Hassan, M. T. J. Phys. B: At. Mol. Opt. Phys. 51, 032005, (2018).

[2]   Miller, R. J. D. Science 343, 1108-1116, (2014).

[3]   Zewail, A. H. Science 328, 187-193, (2010).

[4]   Yang, J. et al. Science 368, 885-889, (2020).

[5]   Hassan, M. T., Baskin, J. S., LiaoB & Zewail, A. H. Nat. Photon. 11, 425-430, (2017).

[6]   Hui, D., Alqattan, H., Sennary, M., Golubev, N. V. & Hassan, M. T. Attosecond Electron Microscopy. arXiv:2305.03014 (2023).

[7]   Alqattan, H., Hui, D., Pervak, V. & Hassan, M. T. APL Photonics 7, 041301, (2022).

[8]   Hui, D. et al. Nat. Photon. 16, 33-37, (2022).

[9]   Hui, D. et al. Science Advances 9, eadf1015, (2023).


Biographical Sketch

Professor Mohammed Hassan is a professor of Physics and Optical Sciences at The University of Arizona (UA). He has 14 years of experience in the Attosecond Physics and Ultrafast Electron Microscopy and imaging research fields. He earned his Ph.D. from Max-Planck Institute for Quantum Optics, Munich, Germany, Prof. Ferenc Krausz group in 2013. He joined Prof. Ahmed H. Zewail’s group at Caltech as a postdoctoral scholar through 2017.  

Earlier in his career, Dr. Hassan developed the light field synthesizer to generate the first optical attosecond pulse, the shortest light pulse documented in the Guinness World Records. Exploiting this tool, he measured the time an electron takes to respond and move. He also used the synthesized waveforms for the generation of extreme ultraviolet radiation from solids, providing a new temporal window into the fundamental physical processes underlying high harmonic generation and electron dynamics in solid-state materials.

As a postdoctoral scholar, working with Nobel laureate Ahmed Zewail, Dr. Hassan optimized ultrafast optical gating techniques for the creation of electron pulses to demonstrate the shortest electron pulse in an electron microscope. He also collaborated in the first imaging of nanoparticle motion dynamics in the liquid state via ultrafast electron microscopy. His early career breakthroughs have been published in high-profile journals.

He is currently well known in his field of attosecond Physics for developing the attosecond electron microscopy “Attomicroscopy”, a camera that will film the electron motion in action. He used this tool to image the electron motion in the solid state. This electron imaging promises to open a new era in ultrafast electron imaging and will lead to many breakthroughs and high-impact scientific achievements. Attomicroscopy imaging opens a new window to the quantum world. A patent for Attomicroscopy has been granted to Dr. Hassan as single inventor.

Moreover, Dr. Hassan developed a high-power “Attosecond Light Field Synthesizer”, to generate synthesized high-power attosecond optical and further to extend control over quantum electron motion into the solid state.  Most recently, he demonstrated all-optical switching of light signals on the attosecond time scale. He achieved this world record optical switching speed by again exploiting the unique light field synthesis capability developed in his lab. Also, he demonstrated the capability to encode data on ultrafast laser pulses, which paves the way to establish attosecond and femtosecond optoelectronics working at the petahertz speed. 

Furthermore, he established a new methodology to sample the light field of ultrafast laser pulses and a new methodology to measure the electronic delay response in the neutral matter.

Dr. Hassan received the international Max-Planck fellowship in 2009. He received the Air Force Young Investigator Award (YIP) in 2019. Hassan also received many prestigious awards for his Attomicroscopy project from the Gordon and Betty Moore Foundation 2018, the W. M. Keck Foundation 2019, and recently the Inaugural AFOSR Director’s Research Initiative (DRI) Award 2022. Moreover, he was awarded 2022 Historically Black Colleges and Universities and Minority-Serving Institutions (HBCUs/MSIs) for his institute. 



Attosecond Electron Microscopy:  imaging the electron motion in action
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