Abstract
Optical components, such as lenses, have traditionally been made in the bulk form by shaping glass or other transparent materials. Recent advances in metasurfaces provide a new basis for recasting optical components into thin, planar elements, having similar or better performance using arrays of subwavelength-spaced optical phase-shifters. The technology required to mass produce them dates back to the mid-1990s, when the feature sizes of semiconductor manufacturing became considerably denser than the wavelength of light, advancing in stride with Moore's law. This provides the possibility of unifying two industries: semiconductor manufacturing and lens-making, whereby the same technology used to make computer chips is used to make optical components, such as lenses, based on metasurfaces. Using a scalable metasurface layout compression algorithm that exponentially reduces design file sizes (by 3 orders of magnitude for a centimeter diameter lens) and stepper photolithography, we show the design and fabrication of metasurface lenses (metalenses) with extremely large areas, up to centimeters in diameter and beyond. Using a single two-centimeter diameter near-infrared metalens less than a micron thick fabricated in this way, we experimentally implement the ideal thin lens equation, while demonstrating high-quality imaging and diffraction-limited focusing.
Highlights
Metasurfaces control the wavefront of light using arrays of fixed optical phase shifters, amplitude modulators, and/or polarization changing elements[1]
We have shown the design, fabrication, and optical characterization of the large area metalenses, 2 centimeters in diameter with efficiency greater than 91%, fabricated using photolithographic steppers
The metalens, which is only 600 nm thick, in combination with the 0.5 mm thick substrate is a close experimental approximation of a lens described by the ideal thin lens equation
Summary
Metasurfaces control the wavefront of light using arrays of fixed optical phase shifters, amplitude modulators, and/or polarization changing elements[1]. By tailoring the properties of each element of the array, one can spatially control these properties of the transmitted, reflected, or scattered light and mold the wavefront[2] Based on this concept, various functionalities have been demonstrated including lenses, axicons, blazed gratings, vortex plates and wave plates[3,4,5,6,7,8,9,10,11]. The data describing large designs are faced with the challenge of enormous file sizes due to having millions or billions of individual microscopic meta-elements (necessitated by the subwavelength size criterion) described over macroscopically large device areas This extremely high data density over large areas generates unmanageably large total file sizes, limiting the fabrication of metalenses to sizes no larger than a few millimeters. Certain conversion software or mask writing machines impose an upper limit on the number of levels that any design may contain (e.g., 16, which was used with our design), so an algorithm based on METAC but limited to 16 levels, which we call METAC16, was included for reference
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