RESUMEN
Switching of light polarization on the sub-picosecond timescale is a crucial functionality for applications in a variety of contexts, including telecommunications, biology and chemistry. The ability to control polarization at ultrafast speed would pave the way for the development of unprecedented free-space optical links and of novel techniques for probing dynamical processes in complex systems, as chiral molecules. Such high switching speeds can only be reached with an all-optical paradigm, i.e., engineering active platforms capable of controlling light polarization via ultrashort laser pulses. Here we demonstrate giant modulation of dichroism and birefringence in an all-dielectric metasurface, achieved at low fluences of the optical control beam. This performance, which leverages the many degrees of freedom offered by all-dielectric active metasurfaces, is obtained by combining a high-quality factor nonlocal resonance with the giant third-order optical nonlinearity dictated by photogenerated hot carriers at the semiconductor band edge.
RESUMEN
Defects in two-dimensional (2D) transition metal dichalcogenides (TMDs) greatly influence their electronic and optical properties by introducing localized in-gap states. Using different non-invasive techniques, we have investigated the spatial distribution of intrinsic defects in as-grown chemical vapor deposition (CVD) MoS2monolayers and correlated the results with the growth temperature of the sample. We have shown that by increasing the CVD growth temperature the concentration of defects decreases and their spatial distribution and type change, influencing the sample's electronic and optical properties.
