Metasurface Optics for Achromatic Imaging Systems

Metasurface optics harness the ability of nanostructured, subwavelength scatterers to mould optical wavefronts on ultrathin, planar platforms. By spatially varying the geometry of individual meta-atoms, these flat optical elements can impart arbitrary phase profiles, enabling lenses, gratings and beam shapers with dramatically reduced thickness and weight compared with conventional refractive or diffractive optics. A primary challenge has been chromatic aberration, whereby dispersion in meta-atom response leads to wavelength-dependent focal shifts and wavefront distortions. Recent advances have addressed this by engineering the spectral phase and group delay of each element so that light across a broad band is brought to a common focus. These developments are paving the way towards fully integrated, full-colour imaging systems with applications ranging from endoscopic probes and wearable displays to high-resolution biomedical microscopes and portable spectrometers. By combining inverse design, dispersion compensation and multi-layer stacking, metasurface imaging elements are achieving near-diffraction-limited performance across the visible and near-infrared, unlocking compact, low-cost instrumentation for global scientific, industrial and consumer markets.

Research from Nature Portfolio

Recent studies have demonstrated dispersion-engineered metasurfaces capable of maintaining uniform phase coverage and minimal aberration from 450 nm to 700 nm, achieving up to 90 % relative diffraction efficiency in both gratings and metalenses. By selecting a set of nano-structures with matched dispersion characteristics but full 0 to 2π phase control, researchers have realised broadband, polarization-insensitive devices that preserve high signal-to-noise ratio over the entire visible range. In parallel, advances in high-index dielectric materials have enabled the fabrication of titanium dioxide metalenses with record-high aspect-ratio nanopillars. Such devices exhibit continuous achromatism from 650 nm to 1000 nm with average efficiencies of 77 %–88 % and numerical apertures from 0.10 to 0.24, directly addressing the near-infrared biological imaging window and demonstrating scalable, large-area manufacturing for practical imaging modules.

Metasurface Optics for Achromatic Imaging Systems publication trend

The graph below shows the total number of articles in metasurface optics for achromatic imaging systems across all publications each year (not limited to Nature Index journals).

Technical terms

Metasurface: A planar assembly of subwavelength scattering elements engineered to tailor the phase, amplitude and polarization of light.

Achromatic: Design characteristic that ensures uniform focal length or optical behaviour across a broad wavelength range, minimising chromatic aberration.

Dispersion engineering: Controlled design of how optical phase or group delay varies with wavelength to counteract inherent chromatic aberration.

Diffraction efficiency: The ratio of light power directed into the desired diffraction order or focus to the incident power, indicating device performance.

Numerical aperture (NA): A dimensionless number characterising the light-gathering ability of a lens, defined by its maximum acceptance angle and the refractive index of the medium.

References

1. Dispersion-engineered metasurfaces reaching broadband 90% relative diffraction efficiency. Nature Communications (2023).
2. High-efficiency broadband achromatic metalens for near-IR biological imaging window. Nature Communications (2021).
3. Real time full-color imaging in a Meta-optical fiber endoscope. eLight (2023).
4. Advance of large-area achromatic flat lenses. Light: Science & Applications (2023).
5. A Multi‐foci Sparse‐Aperture Metalens. Advanced Science (2024).