Schirato, AndreaCrotti, GiuliaZaccaria, Remo ProiettiAlabastri, AlessandroValle, Giuseppe Della2022-06-082022-06-082022Schirato, Andrea, Crotti, Giulia, Zaccaria, Remo Proietti, et al.. "Hot carrier spatio-temporal inhomogeneities in ultrafast nanophotonics." <i>New Journal of Physics,</i> 24, no. 4 (2022) IOP Publishing: https://doi.org/10.1088/1367-2630/ac6009.https://hdl.handle.net/1911/112450Light-induced hot carriers in nanostructures and their corresponding optical nonlinearity have been extensively examined during the last decades. However, nonlinear optical effects dictated by the spatio-temporal evolution of out-of-equilibrium electrons at the nanoscale represent a much more recent research focus. Here we theoretically discuss the role of spatial inhomogeneities that energetic electrons feature across individual nanoantennas in metasurface configuration upon illumination with femtosecond laser pulses. As exemplary cases, we consider two-dimensional geometries of gold meta-atoms having either a high aspect ratio or a tapered cross-section and model their ultrafast optical response. A comparison with numerical results obtained either neglecting or accounting for spatial effects indicates that deep sub-wavelength spatio-temporal transients of carriers may have a significant impact on the dynamics of the all-optically modulated signal, with major quantitative corrections up to predicted changes in sign. Our results present hot-electron local inhomogeneities as an emerging subject with potentially relevant applications in various ultrafast nanophotonic configurations.engOriginal content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.Journal articleSchirato_2022https://doi.org/10.1088/1367-2630/ac6009