Controlling fluorescence emission with split-ring-resonator-based plasmonic metasurfaces

Metasurfaces, which consist of resonant metamaterial elements in the form of two-dimensional thin planar structures, retain great capabilities in manipulating electromagnetic wave and potential applications in modifying interaction with fluorescent molecules. The metasurfaces with magnetic responses are favorable to weakening fluorescence quenching while less investigated in controlling fluorescence. In this paper, we demonstrate control over fluorescence emission by engineering the magnetic and electric modes in plasmonic metasurfaces consisting of 45-nm-thick gold split-ring-resonators (SRRs). The fluorescence emission exhibits an enhancement factor of approximate to 18 and is predominantly x-polarized with assistance of the magnetic mode excited by oblique incidence with an x-polarized electric field. The magnetic and electric modes excited by oblique incidence with a y-polarized electric field contribute to the rotation of emission polarization with respect to the incident polarization. The results demonstrate manipulating the interaction of fluorescent emitters with different resonant modes of the SRR-based metasurface at the nanoscale by the polarization of incident light, providing potential applications of metasurfaces in a wide variety of areas, including optical nanosources, fluorescence spectroscopy and compact biosensors.