ИСТИНА

The polarization, phase, amplitude and frequency of radiation can be effectively controlled by dielectric resonant metasurfaces [1]. High-Q resonances, such as Fano resonances can be used in order to enhance observed effects, including nonlinear ones, for example, the generation of second and third optical harmonics. Promising nowadays active control of radiation parameters is possible due to external perturbations of refractive index by electric or magnetic fields, temperature or optical pulses. It is possible to control the resonance position and achieve a decrease in Q-factor with a single laser pulse in a metasurface. However, it has been possible to achieve a resonance shift accompanied by an increase in Q-factor at ultrashort timescale only theoretically [2]. Here we move forward to vary the metasurface geometry to make fabrication feasible. The sample is an array of germanium rectangular cuboids arranged on top of the silicon ones with a thin silica gap between them. We show numerically that factor increases under optical pump pulse. We also calculate an enhancement of third optical harmonic generation. Our results can be promising for miniature nanophotonics devices. [1] A.I. Kuznetsov, A.E. Miroshnichenko, M.L. Brongersma, Y.S. Kivshar, B. Luk’yanchuk, Optically resonant dielectric nanostructures, Science 354, aag2472 (2016). [2] P.A. Shafirin, V.V. Zubyuk, A.A. Fedyanin and M.R. Shcherbakov, Nonlinear response of Q-boosting metasurfaces beyond the time-bandwidth limit, Nanophot. 11, no. 17, 4053 (2022).