ИСТИНА

Dielectric metasurfaces stand out as a prominent area of research in modern nanophotonics. They offer precise control over light properties through the localization of electromagnetic field at the nanoscale [1]. Remarkable enhancement of optical effects through variation of radiation amplitude, direction, phase, polarization have been demonstrated in many works [2,3]. These effects can be further modulated by external factors like a magnetic field, which changes magneto-optic light characteristics. Even a 5-nm-thick film can effectively enhance magneto-optic intensity and polarization effects [4,5]. For a deeper understanding of the dynamics of electrons and photons, and to determine the mechanisms of relaxation, ultrafast laser pulses are employed. When the pulse duration is comparable to the resonance lifetime, pulse-shaping and all-optical switching effects become observable [6, 7]. However, the ultrafast dynamics of magneto-optical effects in metasurfaces with Mie resonances remain unexplored. By introducing metasurfaces into the optical path of femtosecond lasers, we can dynamically shape the polarization of individual pulses. In this research, a two-dimensional array of silicon nanodisks with a thin layer of nickel on top was examined. The lattice located on a quartz substrate. The resonant wavelength for this metasurface is 810 nm, corresponding to the excitation of magnetic and electric dipole Mie modes. Under resonant conditions, the localization of the electromagnetic field near the upper boundary of the silicon nanodisk increases the effective length of light-nickel interaction. Thus, in a static case, polarization plane rotation is observed to be 1.1 degrees, which is 22 times higher compared to an unstructured nickel film of the same thickness. To experimentally study the intrapulse dynamics of Faraday rotation, a cross-correlation scheme was employed. A laser pulse with a duration 150 femtoseconds interacted with the metasurface. The highest value of polarization plane rotation dynamics was observed at the resonant wavelength. Within the pulse duration, the Faraday effect increased by 0.4 degrees, which corresponds to a 36% modulation. These results qualitatively correlate with numerical simulation data. Our findings pave the way for the development of next-generation magnetophotonic devices with enhanced performance and functionality.