Samsung Advanced Institute of Technology

Compact varifocal lenses are essential to various imaging and vision technologies.
However, existing varifocal elements typically rely on mechanically-actuated systems
with limited tuning speeds and scalability. Here, an ultrathin electrically controlled
varifocal lens based on a liquid crystal (LC) encapsulated semiconductor metasurface
is demonstrated. Enabled by the field-dependent LC anisotropy, applying a voltage
bias across the LC cell modifies the local phase response of the silicon meta-atoms,
in turn modifying the focal length of the metalens. In a numerical implementation,
a voltage-actuated metalens with continuous zoom and up to 20％ total focal shift is
demonstrated. The concept of LC-based metalens is experimentally verified through
the design and fabrication of a bifocal metalens that facilitates high-contrast switching
between two discrete focal lengths upon application of a 3.2 Vpp voltage bias. Owing to
their ultrathin thickness and adaptable design, LC-driven semiconductor metasurfaces
open new opportunities for compact varifocal lensing in a diversity of modern imaging
applications.