On April 27, the research team led by Professor Wenlong Lu from our school published their latest research findings in the prestigious international journal Nature Communications, with a paper entitled "Ultra-dispersive metasurfaces enabled by convergence-phase design using simplified nanopillar arrays." Breaking through classical metasurface phase modulation theories, the team innovatively proposed a convergence-phase design method for manipulating ultra-dispersive optical fields. This approach successfully overcomes the traditional limitation where the range of dispersive optical fields in metasurfaces is restricted by the phase modulation capabilities of nanostructures. By employing simplified nanostructures, the researchers achieved an ultra-large phase variations of 1200π and a massive dispersion range, representing a more than 30-fold improvement over existing methods. Furthermore, they developed a miniaturized chromatic confocal sensor with an unprecedented measuring range of 13mm (compared to the typical range of less than 500μm in current methods), alongside an impressive axial resolution of 50nm. This technology holds broad application prospects in fields such as smart miniature confocal sensing and ultra-large depth-of-field imaging. It is poised to serve critical industrial applications, including the measurement of aero-engine integrally bladed rotors (IBRs), micro-holes in aero-engine main shafts, and micro-channels within spacecraft propulsion systems. Professor Wenlong Lu from our school and Professor Joel K. W. Yang from the Singapore University of Technology and Design (SUTD) are the co-corresponding authors of this paper. Yunquan Wu (2021-cohort Ph.D. student) and Zhichen Cao (2023-cohort Ph.D. student) from our school, along with Professor Hao Wang from Beihang University, are the co-first authors.
Metasurface, owing to their exceptional optical properties and compact, lightweight architectures, offer a promising route to overcome these limitation of conventional optical elements in dispersion and scale. However, to satisfy the demands of simultaneous modulation of the reference wavelength phase and phase dispersion in dispersive optical fields, current methods have relied on highly complex nanostructures with stringent fabrication requirements, typically restricting the achievable phase variations below 40π and dispersion range under 500 μm.
To address this challenge, the team broke through the conventional phase modulation mechanisms of dispersive metasurfaces. By overlapping phase of multiple wavelengths with that of a central wavelength, the broadband phase modulation can be simplified to an equivalent single-wavelength model with modulo-2π wrap-ping. This approach successfully resolves the phase disorder issue that typically arises during the modulo 2π wrapping of broadband dispersion phases, enabling an ultra-large phase modulation of 1200π—a more than 30-fold enhancement over existing approaches (as illustrated in the figure below).
convergence-phase design method
Based on this method, the research team fabricated an ultra-dispersive metasurface utilizing simplified cylindrical nanopillars with an aspect ratio of less than 4 and diameters exceeding 200 nm. The fabricated metasurface features a diameter of 3.6 mm, a numerical aperture (NA) of 0.15, and an axial dispersion range reaching up to 13.27 mm, alongside an average focusing efficiency of 50%. Notably, these low-aspect-ratio and sub-micron diameter cylindrical nanopillars eliminate the need for high-resolution lithography processes, thereby drastically reducing fabrication complexity and costs. This breakthrough lays a solid theoretical foundation for the mass manufacturing and practical application of ultra-dispersive metasurfaces (as shown in the figure below).
Characterization of the ultra-dispersive metasurface
The practicality of this method is fully demonstrated through real-world application validations (as illustrated below). Utilizing the ultra-dispersive metasurface, the research team constructed a spectral tomographic imaging setup capable of achieving a millimeter-level depth of field and a lateral resolution of 1.095 μm. Imaging experiments conducted on human oral epithelial cells and two-photon polymerization (TPP) printed samples revealed that the ultra-dispersive metalens can recover the detailed features of the samples while simultaneously acquiring depth information from different positions (as shown in the figure below).
Apply ultra-dispersive metalens for spectral tomography
Additionally, the research team utilized ultra-dispersive metalenses to design a series of miniaturized chromatic confocal sensors with measuring ranges of 2 mm, 4 mm, and 13 mm, achieving a significantly smaller footprint than their commercial counterparts. Experimental validation confirmed that the 13 mm range sensor achieves an axial resolution of 50 nm. Profilometry experiments were conducted on radar chip packaging components and MEMS scanning micromirror actuators (as shown in the figure below). The results demonstrate that the sensors are capable of capturing complete profiles of the MEMS scanning micromirror while performing high-resolution localized scans to resolve the micrometer-scale features of flexible hinges, showcasing outstanding feasibility for engineering applications.
Chromatic confocal sensors integrated with ultra-dispersive metalenses
This research was supported by the National Natural Science Foundation of China, the National Key R&D Plan, and the Key R&D Plan of Hubei Province, among others.
Original Article: https://doi.org/10.1038/s41467-026-72332-9
