Metalens Enables Parallel Chromatic Confocal Imaging over a Millimeter-Scale Depth Range with an Axial Space-Bandwidth Product of 68.

Abstract

Confocal microscopy provides optical sectioning and micrometer-scale resolution but remains constrained by mechanical axial scanning and bulky optics. Leveraging the intrinsic chromatic dispersion of a custom-designed metalens, we demonstrate parallel confocal depth imaging over a 1.3 mm axial range within a 200 nm visible bandwidth by encoding wavelengths into different axial positions to eliminate mechanical axial scanning, which yields an axial space-bandwidth product (ASBP) of ≈68. A single-mode fiber functions simultaneously as an illumination/collection probe and confocal pinhole, forming a compact design. The system achieves an axial resolution of 11.4 μm (axial sensitivity of 0.15 μm) and a lateral resolution of 2.19 μm near the optimal wavelength of 530 nm. The parallel confocal imaging capability across an extended depth is further validated by depth-resolved imaging and surface profile measurement. This compact, label-free platform underscores the potential of meta-optical chromatic confocal imaging for large-depth, high-resolution microscopic applications.