Active devices and nanoantennas are promising research area of nanophotonics. They can be used to build high-speed elements, optical switches, and sensors. The ultrafast all-optical switches can be represented as semiconductor metasurfaces and nanoantennas, which scattering properties are controlled using femtosecond laser pulses in the pump-probe technique. In this work, the ultrafast dynamics of the light scattering is experimentally investigated for phased arrays of asymmetric sub-wavelength GaAs super-cells consisting of resonators of the various sizes. Energy reallocation of the incident radiation into the different diffraction orders, controlled by the design of the metasurface, was obtained. This effect appears only for the resonant polarization for the structure, as well as at wavelengths close to the optimized value of 800-815 nm. Such energy reallocation is a sign of the phase-manipulation behavior of the metasurface. GaAs metasurfaces are studied by Fourier plane imaging microscopy, in which pump and probe signals of different diffraction orders can be measured independently. The transmission coefficient modulation ∆𝑇⁄𝑇 of the probe pulse in the first diffraction order is shown to be ~15% at a pump fluence of 0.02 μJ/cm^2. The femtosecond relaxation time of free carriers in the GaAs metasurface is ~150 fs. These properties indicate that asymmetric GaAs nanoantennas can be used as all-optical switches.
In this paper we report on fabrication of a nanocomposite based on CdSe quantum dots mixed with commercial photoresist ORMOCOMP and proved its high structurability by direct laser writing. The distribution of quantum dots was visualised by transmission electron microscopy and the quality and geometrical parameters of the structures were studied by optical and atomic force microscopy. We manufactured a novel photonic device for Bloch surface electromagnetic waves in photonic crystals and thoroughly studied their propagation by both leakage microscopy and back focal plane imaging methods. By z-scan method we measured the nonlinear Kerr coefficient of quantum dots. Its high value makes the manufactured photonic device promising for all-optical switching applications.