All-dielectric metasurfaces received great attention in the past years, and they are considered as a novel platform for efficient manipulation of optical beams.  Advances in the design and fabrication of such dielectric metasurfaces have led to the development of several ultra-thin optical metadevices, including flat lenses, beam converters, deflectors and holograms. Being composed of periodic or aperiodic lattices of dielectric nanoparticles, such metasurfaces exhibit low absorption in the infra-red and visible spectral ranges. Low losses allow nanoparticles to exhibit Mie-type resonances with a higher quality-factor in comparison to their plasmonic counterparts.

Most functional dielectric metasurfaces to date are based on static designs, defined through geometrical parameters, such as noparticle shape, size, and array layout. However, in many applications it is crucial to enable dynamic tunability of the device functionality with time. For example, the focal distance of a camera lens needs to be changed when taking pictures of objects at different distances; the position of the ranging beam in driver-less vehicles needs to scan different directions. Therefore, implementing dynamic control over the response of the metasurfaces is of paramount importance for their practical implementation.

In my thesis, I have developed experimental and theoretical approaches to study tunable metasurfaces. I will present different ways to tune all-dielectric metasurfaces by manipulating the refractive index as well as by changing the surrounding environment.