@article{21527,
  abstract     = {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.},
  author       = {Roques-Carmes, Charles and Lin, Zin and Christiansen, Rasmus E. and Salamin, Yannick and Kooi, Steven E. and Joannopoulos, John D. and Johnson, Steven G. and Soljačić, Marin},
  issn         = {2330-4022},
  journal      = {ACS Photonics},
  keywords     = {metasurfaces, inverse design, multilayered metaoptics, 3D printing, topology optimization},
  number       = {1},
  pages        = {43--51},
  publisher    = {American Chemical Society},
  title        = {{Toward 3D-printed inverse-designed metaoptics}},
  doi          = {10.1021/acsphotonics.1c01442},
  volume       = {9},
  year         = {2022},
}