posted on 2022-01-07, 16:39authored byCharles Roques-Carmes, Zin Lin, Rasmus E. Christiansen, Yannick Salamin, Steven E. Kooi, John D. Joannopoulos, Steven G. Johnson, Marin Soljačić
Optical metasurfaces have been heralded
as the platform to integrate
multiple functionalities in a compact form-factor, with the potential
to replace bulky optical components. A central stepping stone toward
realizing this promise is the demonstration of multifunctionality
under several constraints (e.g., at multiple incident wavelengths
and/or angles) in a single device, an achievement being hampered by
design limitations inherent to single-layer planar geometries. Here,
we propose a framework for the inverse design of multilayer metaoptics
via topology optimization, showing that even few-wavelength thick
devices can achieve high-efficiency multifunctionality, such as multiangle
light concentration and plan-achromaticity. We embody our framework
in multiple closely spaced patterned layers of a low-index polymer,
with fabrication constraints specific to this platform enforced in
the optimization process. We experimentally demonstrate our approach
with an inverse-designed 3D-printed light concentrator working at
five different nonparaxial angles of incidence. Our framework paves
the way toward realizing multifunctional ultracompact 3D nanophotonic
devices.