Broadband highly directive 3D nanophotonic lenses

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Publication date
Reference E. Johlin, S. Mann, S. Kasture, A.F. Koenderink and E.C. Garnett, Broadband highly directive 3D nanophotonic lenses, Nature Commun. 9, 4742: 1-8 (2018)
Groups Nanoscale Solar Cells, Resonant Nanophotonics

Controlling the directivity of emission and absorption at the nanoscale holds great promise
for improving the performance of optoelectronic devices. Previously, directive structures have
largely been centered in two categories

nanoscale antennas, and classical lenses. Herein,
we utilize an evolutionary algorithm to design 3D dielectric nanophotonic lens structures
leveraging both the interference-based control of antennas and the broadband operation of
lenses. By sculpting the dielectric environment around an emitter, these nanolenses achieve
directivities of 101 for point-sources, and 67 for
nite-source nanowire emitters; 3× greater
than that of a traditional spherical lens with nearly constant performance over a 200 nm
wavelength range. The nanolenses are experimentally fabricated on GaAs nanowires, and
characterized via photoluminescence Fourier microscopy, with an observed beaming half-
angle of 3.5° and a measured directivity of 22. Simulations attribute the main limitation in the
obtained directivity to imperfect alignment of the nanolens to the nanowire beneath.