Title: Synthetic Motion with a Space-Time Metasurface
Speaker:  Anthony Harwood – Imperial College London
Moderator: Prof. Marco Piccardo, INESC MN
When: July 12, 2024, 11h00 a.m. @ INESC Lx Auditorium (room #9)

ABSTRACT:  The speed of transfer of mass may not be greater than the speed of light, however, the apparent motion of objects may be superluminal Space time modulations of a surface that exhibit superluminal motion have been the topic of myriad theoretical investigations that promise nanoscale control over electromagnetic waves via the Doppler effect and Fresnel drag, whereby a moving medium alters the momentum of light Herein, we use the ultrafast photoexcitation of a 40 nm film of Indium Tin Oxide to generate superluminally travelling modulations, which act as diffractive apertures in both the spatial and temporal domains Through the design of continuous and discrete forms of synthetic motion we use the resulting space time diffraction to demonstrate ultrafast beam steering and spectral synthesis, which may be tuned using the velocity of the travelling modulation This work represents an exciting step towards the realisation of four dimensional metasurfaces and more complex schemes of synthetic motion.