ИСТИНА

Mie-resonant nanophotonic structures made of dielectric and semiconductor materials with high refractive indices are considered as a promising platform for novel functional optical devices [1–2]. To make such structures active different mechanisms have been proposed recently [3–4]. All-optical switching based on photo-induced carrier generation manifests itself as one of the most promising techniques owing to the intrinsic ultrafast speed of this process [5]. However, most experimental demonstrations to date are limited by transmittance or reflection changes missing active beam profile control by such nanophotonic structures. In this work three different examples of the spatial light control with optically tunable nanophotonic structures are presented. First, GaAs metasurface composed of asymmetric nanoparticle trimers is considered. It is shown that such structure can redistribute light energy between different diffraction orders under low-power laser pumping. Experimentally we demonstrate up to 16% modulation at the pump fluence as low as several µJ/cm2 with the characteristic switching time of 1.2 ps. This effect is caused by the non-uniform absorption of the elements forming the metasurface and by consequent change of their resonant properties due to the free-carrier injection mechanism. Second, we consider asymmetric dimer composed of two GaAs nanoparticles combined with integrated waveguide on the dielectric substrate. It is shown than by optical pumping one can control light coupling efficiency to the waveguide through the modification of the nanoantenna scattering profile. Finally, we investigate gradient GaAs metasurface for the ultrafast image processing using Fourier filtering approach. Achieved results can be used for development of ultrafast optical devices capable of the effective low-power spatial light control. [1] A. I. Kuznetsov et al., “Optically resonant dielectric nanostructures,” Science, 354, aaf2472 (2016). [2] M. Decker, I. Staude, “Resonant dielectric nanostructures: a low-loss platform for functional nanophotonics,” J. Opt., 18, 103001 (2016). [3] R. Paniagua-Dominguez et al., “Active and tunable nanophotonics with dielectric nanoantennas”, Proc. IEEE, 749 – 771 (2020). [4] T. Badloe et al., “Tunable Metasurfaces: The Path to Fully Active Nanophotonics”, Adv. Photonics Res., 2, 2000205 (2021). [5] R. Shcherbakov et al., “Ultrafast all-optical switching with magnetic resonances in nonlinear dielectric nanostructures,” Nano Lett., 15, 6985–6990 (2015).