Multi-Channel Electrically Tunable Varifocal Metalens With Compact Multilayer Polarization-Dependent Metasurfaces and...

As an essential module of optical systems, a varifocal lens usually consists of multiple mechanically moving lenses along the optical axis. The recent development of metasurfaces with tunable functionalities holds the promise of miniaturizing varifocal lenses. However, existing varifocal metalenses are hard to combine electrical tunability with a scalable number and range of focal lengths, which limits the practical applications. Our previous work shows that the electrically tunable channels could be increased to 2^N by cascading N polarization-dependent metasurfaces with liquid crystals (LCs). Here, we demonstrate a compact eight-channel electrically tunable varifocal metalens with three single-layer polarization-multiplexed bi-focal metalens and three LC cells. The total thickness of the device is ∼6 mm, while the focal lengths can be switched among eight values within the range of 3.6-9.6 mm (3.6, 4.2, 4.5, 4.9, 6.2, 6.9, 8.4, 9.6 mm). The scheme is scalable in both the number and range of focal lengths, as well as has the advantage of further miniaturization. We believe that our proposal would open new possibilities for miniaturized imaging systems, AR/VR displays, LiDAR, etc.