Combined metagratings for efficient broad-angle scattering metasurface

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DOI http://dx.doi.org/10.1021/acsphotonics.8b01795
Reference V. Neder, A. Alù, Y. Ra’di and A. Polman, Combined metagratings for efficient broad-angle scattering metasurface, ACS Photonics, (2019)
Group Photonic Materials

Spectrally controlled diffusion and reflection of light are key operations for light management in many optical devices. Integration of this operation in complex nanophotonic devices requires a 2D interface that provides tailored spectrum and directivity control. Here, we present a metagrating superstructure that realizes a resonant light reflector with tailored angular scattering profile. Millimeter-sized metasurfaces are built from arrays of combined supercells of 20-50 μm, composed of 5-7 differently pitched metagratings that tailor at will and with large efficiency the angular response. Each supercell is composed of one or more Si Mie resonators, arranged in a periodic array above a Ag back plane and tailored to resonantly scatter light at 650 nm into only the ±1 diffraction orders with very high efficiency. By varying the pitch and supercell design, we can tailor the overall metasurface reflection profile with large flexibility, realizing a broad-angle Lambertian-type scattering metasurface, as well as a large-angle (35-75°) scattering metasurface, both with resonant optical scattering efficiencies above 70%. These ultra-thin structures, fabricated using thin-film deposition, electron beam lithography and reactive ion etching, can find applications for light trapping and spectrum splitting in solar cells and other devices.