title: Metalenses at visible wavelengths: Diffraction-limited focusing and subwavelength resolution imaging.
abstract: Subwavelength resolution imaging requires high numerical aperture (NA) lenses, which are bulky and expensive. Metasurfaces allow the miniaturization of conventional refractive optics into planar structures. We show that high-aspect-ratio titanium dioxide metasurfaces can be fabricated and designed as metalenses with NA = 0.8. Diffraction-limited focusing is demonstrated at wavelengths of 405, 532, and 660 nm with corresponding efficiencies of 86, 73, and 66%. The metalenses can resolve nanoscale features separated by subwavelength distances and provide magnification as high as 170×, with image qualities comparable to a state-of-the-art commercial objective. Our results firmly establish that metalenses can have widespread applications in laser-based microscopy, imaging, and spectroscopy.
authors.affiliation: Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA.
authors.forename: Mohammadreza
authors.initials: M
authors.lastname: Khorasaninejad
authors.affiliation: Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA.
authors.forename: Wei Ting
authors.initials: WT
authors.lastname: Chen
authors.affiliation: Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA.
authors.forename: Robert C
authors.initials: RC
authors.lastname: Devlin
authors.affiliation: Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA. University of Waterloo, Waterloo, ON N2L 3G1, Canada.
authors.forename: Jaewon
authors.initials: J
authors.lastname: Oh
authors.affiliation: Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA.
authors.forename: Alexander Y
authors.initials: AY
authors.lastname: Zhu
authors.affiliation: Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA. capasso@seas.harvard.edu.
authors.forename: Federico
authors.initials: F
authors.lastname: Capasso