All-dielectric metamaterials offer great flexibility for controlling light-matter interaction, owing to their strong electric and magnetic resonances with negligible loss at wavelengths above the material bandgap. Here, we propose an all-dielectric asymmetric metasurface structure exhibiting high quality factor and prominent Fano line shape. Over three-orders photoluminescence enhancement is demonstrated in the fabricated all-dielectric metasurface with record-high quality factor of 1011. We find this strong emission enhancement is attributed to the coherent Fano resonances, which originate from the destructive interferences of antisymmetric displacement currents in the asymmetric all-dielectric metasurface. Our observations show a promising approach to realize light emitters based on all-dielectric metasurfaces.

A resonant metasurface with high quality factor can not only localize light at the nanoscale but also manipulate the far-field radiation. In this work, we experimentally demonstrate an active Fano-resonant metasurface that combines an asymmetric silicon nanorod array with embedded germanium quantum dots. The collective resonance of the nanorods results in strong near-field confinement, and the nanorods also lead to directional emission. This gives rise to 3 orders of magnitude enhancement of the photoluminescence intensity with respect to the unpatterned area. Besides, due to the symmetry-breaking property of the structure, the light emission is of specific polarization. Moreover, by varying the geometric parameters of the nanorods, different resonances are spectrally overlapped, which can be utilized to manipulate the far-field radiation pattern. The metasurface shows enormous potential in manipulating light emission and provides a route for high-directionality, high-efficiency LEDs and potentially functional dielectric metasurface lasers.

A light-emitting toroidal resonant metasurface that demonstrates simultaneous control of spontaneous emission and far-field polarization properties.