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Metasurfaces are two-dimensional arrays of subwavelength scatterers designed to control electromagnetic waves in ways that extend beyond conventional optics. By arranging tiny resonators or antennas with spatially varying geometry, distance, orientation, and material properties, the surface can tailor amplitude, phase, polarization, and dispersion of transmitted or reflected waves across a broad range of frequencies, from radio waves to visible light.

The operating principle relies on local interactions between incident waves and the meta-atoms. Each element imposes a specific phase shift and polarization transformation, and a carefully engineered spatial pattern converts an incoming wavefront into a desired output, often following a generalized Snell’s law. Metasurfaces enable compact lenses, beam deflectors, holograms, polarization converters, and other beam-shaping devices with potentially reduced thickness and weight compared with traditional optics.

Materials and fabrication vary by application. Dielectric and plasmonic materials are common, with dielectric metasurfaces often offering lower loss in the optical regime. Fabrication typically involves lithography, nanoimprint, or etching processes to create subwavelength features. Practical considerations include losses, bandwidth, angular tolerance, and fabrication precision, all of which influence efficiency and performance.

Twisted metasurfaces form a notable subcategory in which unit cells rotate across the aperture to introduce geometric (Pancharatnam–Berry) phase control. This twist enables generation of orbital angular momentum, complex polarization states, and multiplexed or multi-channel wavefront manipulation, expanding the design space for advanced photonic and radio-frequency devices.

Overall, metasurfaces represent a versatile platform for compact, multifunctional wave control, with ongoing research addressing higher efficiency, broader bandwidth, and scalable manufacturing.