Chromatic Meta-Device for Extended-Depth Three-Dimensional Imaging

Achieving large axial range while maintaining high localization accuracy in three-dimensional imaging remains challenging, especially for compact, integrated meta-devices essential in modern sensing systems. Here, we overcome this limitation via a chromatic double-helix (DH) metalens with a diameter of 400 µm and a numerical aperture (NA) of 0.5, which employs a dual-encoding strategy: wavelength provides coarse axial localization, and DH point-spread function (PSF) lobe rotation provides fine localization. Imaging a 5 µm pinhole demonstrates a continuous 650 µm axial detection range across the 480–680 nm spectrum, representing a 5.7-fold extension over a monochromatic counterpart at 550 nm while retaining high precision. Resolving a USAF1951 target across this extended depth further validates its practical imaging capability beyond basic tracking. By integrating depth-dependent functionalities into a single planar meta-device, this work enables extended-depth 3D imaging in a compact architecture and opens new possibilities for miniaturized optical systems.