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Published November 24, 2020 | Supplemental Material
Journal Article Open

Array-Level Inverse Design of Beam Steering Active Metasurfaces


We report an array-level inverse design approach to optimize the beam steering performance of active metasurfaces, thus overcoming the limitations posed by nonideal metasurface phase and amplitude tuning. In contrast to device-level topology optimization of passive metasurfaces, the outlined system-level optimization framework relies on the electrical tunability of geometrically identical nanoantennas, enabling the design of active antenna arrays with variable spatial phase and amplitude profiles. Based on this method, we demonstrate high-directivity, continuous beam steering up to 70° for phased arrays with realistic tunable antenna designs, despite nonidealities such as strong covariation of scattered light amplitude with phase. Nonintuitive array phase and amplitude profiles further facilitate beam steering with a phase modulation range as low as 180°. Furthermore, we use the device geometries presented in this work for experimental validation of the system-level inverse design approach of active beam steering metasurfaces. The proposed method offers a framework to optimize nanophotonic structures at the array level that is potentially applicable to a wide variety of objective functions and actively tunable metasurface antenna array platforms.

Additional Information

© 2020 American Chemical Society. Received: June 16, 2020; Accepted: October 6, 2020; Published: October 30, 2020. The authors thank L. Sweatlock and P. Hon regarding preliminary discussions about the project and Y. Tokpanov for discussions regarding optimization algorithms. The authors acknowledge metasurface device fabrication support provided by the Kavli Nanoscience Institute (KNI). The FDTD computations presented here were conducted on the Caltech High Performance Cluster, partially supported by a grant from the Gordon and Betty Moore Foundation. Author Contributions. P.T. and G.K.S. contributed equally to this work. Author Contributions: P.T., G.K.S., R.S., and H.A.A. conceived the original idea. P.T. analyzed forward design methods, designed the iterative genetic optimization, performed several optimization studies, analyzed the experimental results, and wrote the manuscript. G.K.S. and R.S. performed the design and simulations of the electro-optically tunable metasurface. G.K.S performed the FDTD simulations and numerical design, fabricated the metasurface device, performed the optical measurements, and extracted the experimental data. K.T.F. helped with the analysis of forward design methods and the design of the genetic algorithm. R.S. and M.G. supported in designing theoretical studies and performing data analysis. G.K.S. and M.G. built the experimental setup. H.A.A. organized the project, designed optimization studies, analyzed the results, and prepared the manuscript. All authors have given approval to the final version of the manuscript. This work was supported by National Aeronautics and Space Administration (NASA) Early Stage Innovation (ESI) Grant 80NSSC19K0213 and Samsung Electronics. The authors declare no competing financial interest.

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August 20, 2023
October 20, 2023