Light diffraction in all-optical time-varying metasurfaces
File(s)
Author(s)
Tirole, Romain
Type
Thesis
Abstract
This thesis focuses on frequency control of optical waves using time-varying effects in nanophotonic media. Particularly, diffraction by a slit in time is demonstrated using ultrafast all-optical mirrors. We first demonstrate a large reflectivity change from an Indium Tin Oxide/Gold bilayer under optical pumping, at speeds high enough to observe time-varying effects. Then, treating the mirror as an interface, we show time-diffraction from the sample, corresponding to broadening and shifting of the spectrum of light reflected by the mirror during its modulation. This is clearly confirmed by a double slit diffraction experiment, replicating Young's experiment in time, with a generated spectrum exhibiting oscillations in frequency. Insights on the electron dynamics within Indium Tin Oxide is gained, with in particular a striking shortening of the permittivity modulation rise time unlocking the access to an even lower timescale for time-varying effects. Finally, time-varying effects on harmonic generation from Indium Tin Oxide and Gallium Phosphide thin films are demonstrated, exhibiting strong temporal refraction and new mechanisms for temporal modulation.
Version
Open Access
Date Issued
2023-06
Date Awarded
2023-09
Copyright Statement
Creative Commons Attribution NonCommercial Licence
License URL
Advisor
Sapienza, Riccardo
Maier, Stefan
Sponsor
Engineering and Physical Sciences Research Council
Grant Number
2277247
Publisher Department
Physics
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)