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.
Highlights
Subwavelength resolution imaging requires high numerical aperture (NA) lenses, which are bulky and expensive
Typical high-NA objectives consist of precisionengineered compound lenses which make them bulky and expensive, limiting their applications and hindering their integration into compact and cost-effective systems
Singlet planar lenses with high NA in the visible range are in high demand due to their potential widespread applications in imaging, microscopy, and spectroscopy
Summary
Subwavelength resolution imaging requires high numerical aperture (NA) lenses, which are bulky and expensive. Simulations using a commercial finite difference time domain (FDTD) solver (Lumerical Inc., Vancouver) in Fig. 1F show that conversion efficiencies as high as 95% are achieved and that the metalens can be designed for a desired wavelength via tuning of nanofin parameters. The metalenses’ focal spot profiles and efficiencies were measured using the experimental setup shown in fig.
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