Figure 2: Design of anapole nanolaser.
Figure 2
(a) Tunability of the direct bandgap of InxGa(1?x)As as a function of the molar ratio x of InAs. (b) Pseudocolour plot of the scattering cross-section Csca of an In0.15Ga0.85As nanodisk for a varying disk diameter d and of the incident wavelength. The incident field is linearly polarized along the Ex direction. The white dashed line LED Down Light the region where the scattering is suppressed by the presence of anapole states. (c) Scattering cross-section for an In0.15Ga0.85As nanodisk of diameter d=440?nm and height h=100?nm. For these choice of parameters, the anapole wavelength coincides with the semiconductor emission wavelength λ0 (red arrow). The red shaded area shows the Lorentzian gain profile of the In0.15Ga0.85As semiconductor that is entirely contained in the scattering suppression region.
Full size image
Figure 2b illustrates the scattering cross-section Csca33 of a nanodisk of In0.15Ga0.85As with height 100?nm and different values of diameter d. The figure shows a region where the scattering of the nanodisk is suppressed in all directions (see Fig. 2b dashed line). Such special region, which extends in the visible and in the near infrared for In0.15Ga0.85As nanodisks, is sustained by the presence of non-radiating anapole states that do not possess far-field emission. This is further confirmed by the multipole decomposition of the electromagnetic fields as a function of the incident wavelength for a nanodisk with diameter d=440?nm and height h=100?nm (Supplementary Figs 2–5).