Nonlinear optical response of embedded-semiconductor quantum dots covered by plasmonic metasurfaces

We report the first experimental finding of nonlinear responses of photoluminescence (PL) intensity in coupling systems of plasmonic metasurface and InAs quantum dots (QDs) embedded in a GaAs substrate. We numerically designed the coupling systems and experimentally studied the PL at room temperature (RT). We found that even weak excitation induces superlinear response of the PL intensities. For comparison, we fabricated and tested a series of metallic grating couplers on the QD-embedded GaAs substrate. Although the excitation light efficiently couples to grating structures, we found that the degree of nonlinearity of the PL assisted by the plasmonic metasurfaces is higher than the case of the grating structures. These results indicate that the coupled systems of QD emitters and the plasmonic metasurfaces are essentially nonlinear systems.