Abstract
Abstract Metasurface lenses (metalenses) offer an ultrathin and simple optical system with dynamic functions that include focal length tuning. In this study, a rotational varifocal (i.e., moiré) metalens based on octagonal single-crystal silicon pillars was designed and fabricated to realize a high transmittance, whole 2π phase coverage, and polarization insensitivity for visible wavelengths. The moiré metalens consists of a pair of cascaded metasurface-based phase lattices and the focal length can be adjusted from negative to positive by mutual rotation. The fabricated moiré metalens demonstrated a focal length that can be tuned from −36 mm to −2 mm and from 2 to 12 mm by mutual rotation from −90° to 90°, and the experimental measurements agreed well with theoretical values at the design wavelength of 633 nm. Imaging was demonstrated at three distinct wavelengths of 633, 532, and 440 nm.
Highlights
Metasurfaces are a planar type of metamaterial and are promising as optical components
A rotational varifocal metalens based on octagonal single-crystal silicon pillars was designed and fabricated to realize a high transmittance, whole 2π phase coverage, and polarization insensitivity for visible wavelengths
Rotational varifocal metalenses, which are known as moiré metalenses, consist of a pair of two metasurfaces
Summary
Metasurfaces are a planar type of metamaterial and are promising as optical components. Rotational varifocal metalenses, which are known as moiré metalenses, consist of a pair of two metasurfaces. Their focal length can be tuned by mutual rotation. Moiré metalenses have the advantages of compactness along the optical axis, an unchanged aperture size, and a wide tuning range from negative to positive focal lengths. Luo et al [49] recently demonstrated a moiré metalens for the visible wavelength of 532 nm, its tuning range was limited to the positive region. A moiré metalens for visible wavelengths and with both negative and positive focal length tuning was designed and fabricated by using single-crystal silicon octagonal pillars. Imaging at three distinct wavelengths of 633, 532, and 440 nm was demonstrated
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