LASSP & AEP Seminar: Mohammed Hassan (Arizona)

What can we see with the world’s fastest electron microscope?

Ultrafast Electron Diffraction and Microscopy imaging have been demonstrated to be pivot tools for imaging atomic motion in real time and space 1,2. The generation of a few hundred femtoseconds electron pulses enabled recording movies for molecular and atomic motion 3. However, the technical challenges in electron pulse compression have limited the temporal resolution of electron imaging experiments to a hundred femtoseconds. Today, I will present our recent work and how we achieved the attosecond (attosecond =10-18 second) temporal resolution in the transmission electron microscope4 to establish what we so-called “attomicroscope”. The attomicroscope is considered the world’s fastest electron microscope, which enables us to image and control the electron motion dynamics in graphene. I will present our attosecond electron diffraction results, which carry the signature of the electron density distribution dynamics 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 material sciences, physics, chemistry, and biochemistry 4,5. In material sciences, one of the most critical applications of attomicroscopy electron imaging is the capability to connect the light-induced electron dynamics and the material’s morphology. This connection builds the bridge between the physics findings and the engineering applications and helps to develop ultrafast optoelectronics. As proof-of-principle, I will present how understanding electron dynamics in graphene by attomicroscopy imaging empowered us to generate, log, and control light-induced current in a graphene phototransistor and demonstrate the attosecond current switching with petahertz speed 6.

How can electron motion control in materials open the door to developing the future electronics? 7
In the second part of my talk, I will present our development of the light field synthesizer device, which we used for the on-demand tailoring of light field waveforms 8. We utilized complex synthesized waveforms to demonstrate the quantum electron motion control in dielectric material 9. This fine control allowed for switching the optical signal (ON/OFF) with sub-femtosecond time resolution 10. Furthermore, we demonstrated the encoding of binary data (1 &0) 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.

References
1. Zewail, A. H. Science 328, 187-193, (2010).
2. Hassan, M. T. J. Phys. B: At. Mol. Opt. Phys. 51, 032005, (2018).
3. Yang, J. et al. Science 368, 885-889, (2020).
4. Hui, D., Alqattan, H., Sennary, M., Golubev, N. V. & Hassan, M. T. Science Advances 10, eadp5805, (2024).
5. Hassan, M. T. Physics Today 77 38–43 (2024).
6. Sennary, M. et al. Light-induced quantum tunnelling current in graphene. arXiv:2407.16810 (2024).
7. Hassan, M. T. ACS Photonics 11, 334-338, (2024).
8. Alqattan, H., Hui, D., Pervak, V. & Hassan, M. T. APL Photonics 7, 041301, (2022).
9. Hui, D. et al. Nat. Photon. 16, 33-37, (2022).
10. Hui, D. et al. Science Advances 9, eadf1015, (2023).