Colloquium November 20 - Metamaterials that vary in time unlock superluminal motion

by Prof. Riccardo Sapienza (Imperial College London)

Thursday 20 Nov 2025, 15:00 → 16:30 Europe/Rome

1/1-1 - Aula "A. Rostagni" (Dipartimento di Fisica e Astronomia - Edificio Marzolo)

Speaker: Prof. Riccardo Sapienza

Affiliation: Imperial College London

Date: November 20th, 2025, 3 p.m.

Where: Aula Rostagni 

Abstract: Metamaterials have revolutionised the way we control light transport and generation. Yet, to date, they rely on static and passive architectures, only redistributing incident wave energy - for example a metalens that focuses light or a cloak that makes an object invisible. The next frontier is to control metamaterials in space and time, and make waves from the past and future to interact. 
Riccardo Sapienza will discuss the first steps towards temporal control and experiments on double-slit time diffraction at optical frequencies in time-varying metamaterials [1]. Intertwining space and time, he will discuss the observation of scattering of light from optical modulations traveling faster than the speed of light [2], and coherent perfect absorption [3] and how this will enable the simulation of more complex spatio-temporal optical and relativistic phenomena.

References
[1] Double-slit time diffraction at optical frequencies, Romain Tirole, Stefano Vezzoli, Emanuele Galiffi, Iain Robertson, Dries Maurice, Benjamin Tilmann, Stefan A Maier, John B Pendry, Riccardo Sapienza, Nature Physics 19, 999 (2023).
[2] Super-luminal Synthetic Motion with a Space-Time Optical Metasurface  A. C. Harwood, S. Vezzoli, T. V. Raziman, C. Hooper, R. Tirole, F. Wu, S. A. Maier, J. B. Pendry, S. A. R. Horsley, R. Sapienza, Nature Communications 16, 5147 (2025)
[3] Optical coherent perfect absorption and amplification in a time-varying medium, Emanuele Galiffi, Anthony C. Harwood, Stefano Vezzoli, Romain Tirole, Andrea Alù, Riccardo Sapienza, Nature Photonics in press and ArXiV 2410.16426 (2025)

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