Rotationally tunable varifocal 3D metalens

Varifocal optics have a variety of applications in imaging systems. Metasurfaces offer control of the phase, transmission, and polarization of light using subwavelength engineered structures. However, conventional metasurface designs lack dynamic wavefront shaping which limits their application. In this work, we design and fabricate 3D doublet metalenses with a tunable focal length. The phase control of light is obtained through the mutual rotation of the singlet structures. Inspired byMoire lenses, the proposed structure consists of two all-dielectric metasurfaces. The singlets have reverse-phase profiles resulting in the cancellation of the phase shift in the nominal position. In this design, we show that the mutual rotation of the elements produces different wavefronts with quadratic radial dependence. Thus, an input plane wave is converted to spherical wavefronts whose focal length depends on the rotation. We use a combination of a nanopillar and a phase plate as the unit cell structure working at a wavelength of 1500 nm. Our design holds promise for a range of applications such as zoom lenses, microscopy, and augmented reality. (C) 2021 Optical Society of America

Automated summary

Varifocal optics have various applications in imaging systems. In this work, a 3D doublet metalens with a tunable focal length is designed and fabricated, allowing for phase control of light through mutual rotation of singlet structures to produce different wavefronts converting input plane waves into spherical wavefronts whose focal length depends on rotation. The design holds promise for applications such as zoom lenses, microscopy, and augmented reality.