Dr. Tom Siday
University of Birmingham
Tom is an Assistant Professor in the School of Physics and Astronomy at the University of Birmingham. Prior to this, he was a Postdoctoral Researcher and Junior Research Fellow at the University of Oxford, and at the University of Regensburg in Germany. Tom obtained his PhD in Electronic and Electrical Engineering from University College London, where he focused on developing innovative methods to enhance the sensitivity of terahertz microscopes. His research merges terahertz and ultrafast spectroscopy with nano- and atomic-scale microscopy in order to sample the real-space and real-time evolution of quantum systems.
Abstract:
Atomic nonlinearities bring ultrafast optical spectroscopy to the shortest lengthscales
Sampling the interaction of light and matter over the smallest possible length- and timescales has been a long-sought goal in both photonics and condensed matter physics. By exploiting linear evanescent fields confined to miniscule objects, near-field microscopy can access ultrafast light-matter interaction on nanometer length scales [1]. In this talk, I will first discuss several recent applications of ultrafast near-field microscopy. Then, I will demonstrate a fundamentally new paradigm for ultrafast microscopy which exploits strong atomic nonlinearities within optical near-fields. In doing so, simultaneous atomic-scale spatial resolution and subcycle time resolution become possible [2]. This emergent nonlinear response originates from electromagnetic radiation emitted by tunnelling currents flowing in response to the THz electric field [3,4]. This fundamentally new imaging mechanism - near-field optical tunnelling emission (NOTE) - provides the first subcycle videography of atomic-scale quantum dynamics.
[2] T. Siday et al., “All-optical subcycle microscopy on atomic length scales”, Nature, 629, 329 (2024).
[3] T. L. Cocker et al., “An ultrafast terahertz scanning tunnelling microscope”, Nat. Photonics, 7, 620 (2013).
[4] T. L. Cocker et al., “Tracking the ultrafast motion of a single molecule by femtosecond orbital imaging”, Nature, 539, 263 (2016).
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