Focal length adjustable metalenses for zoom imaging

Abstract

Lenses with tunable focal length are crucial to the operation of many optical systems, as in photography, mixed reality, and microscopy. Various technologies exist that support this behavior, but they often entail high power consumption and rely on bulky and expensive optical components. With recent advances in metasurface optics in miniaturizing and augmenting traditional systems, these devices may enable the next generation of varifocal lenses. These devices are flat optical elements comprising arrays of subwavelength-spaced scatterers that can impart spatially varying phase, amplitude, and polarization changes on wavefronts. In recent years, this field has attracted substantial research interest and has produced several demonstrations of focal length adjustable metalenses. These techniques, however, often rely on high control voltages to apply a strain to a flexible substrate or depend on microelectromechanical actuators that require sophisticated fabrication and cannot scale to large area apertures. Here, we discuss our work developing and building a 1 cm aperture Alvarez lens metasurface system with which we demonstrate a focal length tuning range of 6 cm (>200% change) at 1550 nm wavelength. We also design 1 mm Alvarez lens-inspired higher order metasurfaces for full-color imaging when combined with post-capture deconvolution. Using both designs, we demonstrate varifocal zoom imaging.