A hybrid achromatic metalens

• Published in: Nature communications Vol. 11; no. 1; p. 3892
• Main Authors: Balli, F., Sultan, M., Lami, Sarah K., Hastings, J. T.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 04.08.2020; Nature Publishing Group; Nature Portfolio
• Subjects: 142/126; 147/135; 639/624/399/1015; 639/624/400/1113; 639/925/927/1021; Aberration; Computer simulation; Diffraction; Direct laser writing; Efficiency; Humanities and Social Sciences; Mass production; multidisciplinary; Numerical aperture; Optical components; Phase plates; Ray tracing; Refractivity; Science; Science (multidisciplinary); Search algorithms; Size reduction; Wavelength
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-020-17646-y

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. Metalenses that correct chromatic aberration also suffer from reduced focusing efficiency. Here, the authors introduce a Hybrid Achromatic Metalens which merges a metalens and phase plate to offer improved focusing efficiency over a broad wavelength range and diffraction limited imaging performance.