Varifocal zoom imaging with large area focal length adjustable metalenses

Abstract

Varifocal lenses are essential components of dynamic optical systems with\napplications in photography, mixed reality, and microscopy. Metasurface optics\nhas strong potential for creating tunable flat optics. Existing tunable\nmetalenses, however, typically require microelectromechanical actuators, which\ncannot be scaled to large area devices, or rely on high voltages to stretch a\nflexible substrate and achieve a sufficient tuning range. Here, we build a 1 cm\naperture varifocal metalens system at 1550 nm wavelength inspired by an Alvarez\nlens, fabricated using high-throughput stepper photolithography. We demonstrate\na nonlinear change in focal length by minimally actuating two cubic phase\nmetasurfaces laterally, with focusing efficiency as high as 57% and a wide\nfocal length change of more than 6 cm (> 200%). We also test a lens design at\nvisible wavelength and conduct varifocal zoom imaging with a demonstrated 4x\nzoom capability without any other optical elements in the imaging path.\n