High-resolution trapped-ion fluorescence imaging via an integrated metalens

We demonstrate the first integration of a metalens inside the ultra-high-vacuum (UHV) chamber of an ion trap, enabling near-diffraction-limited imaging of trapped ions. A single trapped Yb⁺ ion is laser-cooled close to the Lamb-Dicke regime to characterize the metalens performance, achieving a full-width at half-maximum (FWHM) of 1.16 ± 0.09 μm, which aligns closely with the Abbe diffraction limit of 1.15 μm and outperforms conventional external-cavity lenses (2.37 ± 0.12 μm) with the same numerical aperture. We further demonstrate near-diffraction-limited imaging of multi-ion systems over the accessible off-axis range. Our results establish the metalens as a superior optical element for ion fluorescence imaging, providing higher resolution for applications in ion position calibration, multi-qubit readout, and precision measurement. Furthermore, this miniaturized and integrable approach overcomes traditional optical constraints, delivering near-diffraction-limited imaging and advancing the development of compact ion trap platforms.