Dielectric metasurfaces made from vertically oriented nanoresonators
Dielectric metasurfaces control optical wavefronts via nanoscale resonators laid out across a surface. However, most metasurfaces are, by design, planar. In this work, we demonstrate the ability to fabricate dielectric metasurfaces with vertically oriented dielectric resonators using membrane projection lithography. We first numerically characterize the resonant modes of an array of vertically oriented germanium ellipses with no substrate and identify a narrowband region where the resonators satisfy the first Kerker condition. We then fabricate seven metasurfaces by depositing germanium ellipses onto walls of a 3D micrometer-sized silicon nitride photonic scaffold and characterize their transmission. We find that signatures of the multipolar modes seen in the unsupported array persist in the supported array, but the overall behavior is more complicated due to the scaffold. Further, we show that for a conceptual metasurface containing two coupled, vertically oriented ellipses, the ellipses can generate a sharp resonance with a quality factor of 240.