Multiple Fano Resonances in Symmetry-Breaking Silicon Metasurface for Manipulating Light Emission

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.