Optical metasurfaces are two-dimensional arrays of subwavelength structures which effectively control light characteristics, such as polarisation, amplitude, and phase. The metasurface optical behaviour originates from the collective electromagnetic wave resonance within the nanostructures and allows the development of a new type of integrated photonic devices, such as phase-matching-free nonlinear wavelength convertors and convolutional image processors. However, because of the fixed geometry of the metasurface structural units, finding a reversible and dynamic way to alter their optical output is a challenge to overcome.

In this seminar, I will discuss polarisation tuning as a tool to control the third-harmonic generation process in metasurfaces. Then, I will cover exploiting the thermo-optical effect for dynamically altering metasurface optical response and forming tunable images. Next, I will show utilising localised transparent micro-heaters and electrical switching for programming the scattering properties of the metasurfaces capable of delivering a sub-millisecond switching speed. I will conclude my talk by presenting our work on the ultrafast tuning of metasurfaces with a high absolute transmission modulation above 20% as a viable method for switching metasurface optical characteristics.