Metalenses
Metalenses are planar optical elements composed of metasurfaces—two-dimensional arrays of subwavelength nanostructures that impart spatially varying phase to transmitted light. By engineering the geometry of each scattering element, a metalens can produce the same wavefront as a conventional curved lens but in a thin, flat form factor. There are two common phase-control approaches: propagation phase, where the resonant response of a nanoscale pillar provides a local phase shift, and geometric phase (Pancharatnam-Berry phase), where rotation of anisotropic elements converts polarization state into a phase shift.
Fabrication uses nanoscale lithography on substrates such as glass or silicon, with common materials including TiO2,
Applications include compact imaging lenses for smartphone cameras, microscopy, augmented reality, LiDAR, and space- and fiber-optic