What Is a Metalens?

A metalens is a thin, flat optical element that uses a carefully engineered pattern of subwavelength structures to control how light propagates. Unlike a conventional lens, which relies on a curved bulk profile to bend rays, a metalens uses a surface with nanoscale features known as meta-atoms. Each meta-atom locally modifies the phase, amplitude, and sometimes polarization of the incoming wave.

The central idea is simple: if we can impose the correct phase delay across a surface, we can reshape a plane wave into a converging or diverging wavefront. A metalens does exactly that, but without the depth and curvature of a traditional glass lens. This makes it possible to build optics that are extremely thin, lightweight, and compatible with compact devices such as cameras, sensors, augmented reality systems, and microscopes.

In practice, the metalens is a two-dimensional analog of a refractive lens. The local phase profile is designed so that light from a distant object is brought to a focus at a chosen plane. The phase control is distributed over the aperture, not produced by a gradual change in material thickness. That is the key distinction between a metalens and a conventional lens.

Key ideas

  • A metalens is a flat optical surface, not a curved piece of glass.
  • The surface is patterned with subwavelength meta-atoms.
  • These nanostructures impose a spatial phase profile that focuses light.
  • The result is a thinner, lighter optical element with high design flexibility.

A metalens replaces bulk curvature with engineered phase control on a surface.

Metalens with different focal length and deflection angles

Image source: Wikimedia Commons, “Metalens with different focal length and deflection angles” (CC BY-SA 4.0).

References

[1] Wikipedia contributors. “Metalens.” https://en.wikipedia.org/wiki/Metalens

[2] Khorasaninejad, M., Chen, W. T., Devlin, R. C., Oh, J., Zhu, A. Y., & Capasso, F. (2016). Metalenses at visible wavelengths: diffraction-limited focusing and subwavelength resolution imaging. Science, 352(6290), 1190–1194. https://www.science.org/doi/10.1126/science.aaf1110

[3] Wikipedia contributors. “Metasurface.” https://en.wikipedia.org/wiki/Metasurface

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