Metalenses, ultra-thin optical elements that focus light using subwavelength structures, have been the subject of a number of recent investigations. Compared to their refractive counterparts, metalenses offer reduced size and weight, and new functionality such as polarization control. However, metalenses that correct chromatic aberration also suffer from markedly reduced focusing efficiency. Here we introduce a Hybrid Achromatic Metalens (HAML) that overcomes this trade-off and offers improved focusing efficiency over a broad wavelength range from 1000-1800 nm. HAMLs can be designed by combining recursive ray-tracing and simulated phase libraries rather than computationally intensive global search algorithms. Moreover, HAMLs can be fabricated in low-refractive index materials using multi-photon lithography for customization or using molding for mass production. HAMLs demonstrated diffraction limited performance for numerical apertures of 0.27, 0.11, and 0.06, with average focusing efficiencies greater than 60% and maximum efficiencies up to 80%. A more complex design, the air-spaced HAML, introduces a gap between elements to enable even larger diameters and numerical apertures.
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This work was supported in part by Intel Corporation. Additional support for this work was provided by the Reese S. Terry professorship in Electrical Engineering at the University of Kentucky. This work was performed in part at the U.K. Center for Nanoscale Science and Engineering and the U.K. Electron Microscopy Center, members of the National Nanotechnology Coordinated Infrastructure (NNCI), which is supported by the National Science Foundation (ECCS-1542164). This work used equipment supported by National Science Foundation Grant No. CMMI-1125998.
The data that support the plots and findings of this paper are available in the supplementary information and from J.T.H. upon reasonable request. Source data is provided with this paper and is available for download as an additional file listed at the end of this record.
Balli, Fatih; Sultan, Mansoor A.; Lami, Sarah K.; and Hastings, J. Todd, "A Hybrid Achromatic Metalens" (2020). Electrical and Computer Engineering Faculty Publications. 39.