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Nonscattering-to-Superscattering Switch with Phase-Change Materials

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journal contribution
posted on 23.07.2019, 21:43 by Sergey Lepeshov, Alex Krasnok, Andrea Alù
Phase-change materials (PCMs) can switch between different crystalline states as a function of an external bias, offering a pronounced change of their dielectric function. To take full advantage of these features for active photonics and information storage, stand-alone PCMs are not sufficient because the phase transition requires strong pump fields. Here, we explore hybrid metal–semiconductor core–shell nanoantennas loaded with PCMs, enabling a drastic switch in scattering features as the load changes its phase. Large scattering, beyond the limits of small resonant particles, is achieved by spectrally matching different Mie resonances, while scattering cancellation and cloaking is achieved at anapole state with out-of-phase electric dipole oscillations in the PCM shell and Ag core. We show that by tuning the PCM crystallinity, we can largely vary total (∼15 times) and forward (∼100 times) scattering. Remarkably, a substantial reconfiguration of the scattering pattern from Kerker (zero backward) to anti-Kerker (almost zero forward) regimes with little change (∼5%) in crystallinity is predicted, which makes this structure promising for low-intensity nonlinear photonics.