High-efficiency, large-area, topology-optimized metasurfaces

Abstract

Metasurfaces are ultrathin optical elements that are highly promising for constructing lightweight and compact optical systems. For their practical implementation, it is imperative to maximize the metasurface efficiency. Topology optimization provides a pathway for pushing the limits of metasurface efficiency; however, topology optimization methods have been limited to the design of microscale devices due to the extensive computational resources that are required. We introduce a new strategy for optimizing large-area metasurfaces in a computationally efficient manner. By stitching together individually optimized sections of the metasurface, we can reduce the computational complexity of the optimization from high-polynomial to linear. As a proof of concept, we design and experimentally demonstrate large-area, high-numerical-aperture silicon metasurface lenses with focusing efficiencies exceeding 90%. These concepts can be generalized to the design of multifunctional, broadband diffractive optical devices and will enable the implementation of large-area, high-performance metasurfaces in practical optical systems.

MetaNet: a new paradigm for data sharing in photonics research

“…While the MetaNet library currently contains only unit cells of periodic deflectors, it is possible to stitch many of these unit cells together from differing devices to create an aperiodic device such as a metalens. This concept of constructing metasurfaces through the stitching of wavelength-scale unit cells has been previously demonstrated in [19] and [46]. Here, we stitch high deflection angle unit cells from MetaNet, which are designed to deflect TE polarized light to angles ranging from 55 • to 75 • , to create an off-axis metalens.…”

“…In the future, we will expand the database to include a wider scope of materials, including other variants of silicon, such as crystalline [37] and amorphous silicon [38], as well as titanium dioxide [39,40] and silicon nitride [41,42], which are commonly used for visible light applications. We will also include devices with more diverse functionalities, such as polarization control, as well as wavelength-scale scattering elements that can be stitched together to create aperiodic structures [19].…”

“…For example, elements in planar chip-based photonic systems, such as ring resonators, mode converters, and demultiplexers, consist of simple shapes based on the coupling or tapering of waveguide structures. Similarly, diffractive optics in the form of metasurfaces [16][17][18][19][20] and metamaterials utilize 'meta-atoms,' which consist of nanoresonators or nanowaveguides with intuitive optical responses. The use of simple shapes is advantageous as it enables the design process to be guided by physical intuition and allows devices to be realized using relatively simple design rules.…”

Multifunctional volumetric meta-optics for color and polarization image sensors

“…Thus, we experimentally validate the fabrication-constrained design using a centimeter-scale analog ( Fig. 3) operating at microwave frequencies in the Ka band (26)(27)(28)(29)(30)(31)(32)(33)(34)(35)(36)(37)(38)(39)(40). This device is designed to maximize the sorting efficiency at 18 wavelengths, equally spaced across the Ka band, and for both orthogonal linear polarizations.…”

“…Beyond imaging, we may tailor each pixel to collect a spectrum of interest, such as chemical fluorescence, for use in remote sensing applications [28]. Finally, this approach could be used to control the scattering based on the spatial mode of incident light for high-NA imaging [29], angular selectivity in photovoltaics [30], or automatic object recognition [31].…”