Ultrafast, all-optical, and highly efficient imaging of molecular chirality

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• David Ayuso Molinero (Imperial College London)
• Wednesday 05 April 2023, 14:00-15:00
• Physics West 115.

If you have a question about this talk, please contact Dr Miguel Navarro-Cia.

Chirality is a universal type of asymmetry that naturally arises in molecules, optical fields, viruses, or even galaxies. Just like a chiral glove would either fit our left or right hand, but not both, the two non-superimposable mirror-reflected versions of a chiral molecule (enantiomers) can behave very differently when they interact with another chiral entity, e.g. another chiral molecule. It is therefore unsurprising that methods for detecting, quantifying and manipulating molecular chirality are of great importance and interest, particularly in biochemical and pharmaceutical contexts. Traditional chiro-optical methods rely on the (chiral) helix that circularly polarised light draws in space. However, the micron-scale pitch of this helix, determined by the wavelength, is orders of magnitude larger than the Angstrom-scale size of the molecules. As a result, the tiny molecules perceive this helix as a planar circle, hardly feeling its chirality. This leads to extremely weak enantio-sensitivity and creates a justified impression that chiral discrimination is difficult, particularly on ultrafast timescales. We can overcome this fundamental limitation by creating synthetic chiral light [1], which is locally chiral: tip of the electric-field vector draws a chiral (three-dimensional) Lissajous figure in time, at each point in space. It allows us to suppress the nonlinear optical response of a selected molecular enantiomer while maximising it in its mirror twin. In this seminar, I will show how we can shape the polarisation of light in time and in space in order to maximise the enantio-sensitive response of chiral molecules on ultrafast timescales [1-7]. As we shall see, by controlling the sub-cycle temporal structure of the driving laser field, we can imprint the medium’s handedness into different enantio-sensitive observables: the total intensity of harmonic light [1-3], the direction of harmonic emission [3-5], or the polarisation of the nonlinear optical response [6,7]. Our numerical and semi-analytical modelling reveals that, in all these cases, we can reach the ultimate limit of enantio-efficiency: 100%. This creates exciting opportunities for imaging chiral molecules and ultrafast chiral dynamics, as well as new routes for enantio-sensitive control of chiral matter.

[1] D. Ayuso, O. Neufeld, A. F. Ordonez, P. Decleva, G. Lerner, O. Cohen, M. Ivanov, and O. Smirnova, Nature Photonics 13, 866 (2019) [2] D. Ayuso, Phys. Chem. Chem. Phys. 24, 10193-10200 (2022) [3] L. Rego and D. Ayuso, ArXiv:2206.01680 [4] D. Ayuso, A. F. Ordonez, P. Decleva, M. Ivanov and O. Smirnova, Nature Communications 12, 3951 (2021) [5] L. Rego and D. Ayuso, to be published in Nanophotonics (2022), ArXiv:2206.01719 [6] D. Ayuso, A. F. Ordonez, M. Ivanov and O. Smirnova, Optica 8, 1243 (2021) [7] O. Neufeld, D. Ayuso, P. Decleva, M. Y. Ivanov, O. Smirnova and O. Cohen, Physical Review X 9 , 031002 (2019)

This talk is part of the Metamaterials Research Group Seminars series.

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• Bham Talks
• Metamaterials Research Group Seminars
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