Presentation description

Confocal microscopy exploits the wave nature of light by projecting it through a small aperture to capture its geometric shadow. As aperture size decreases, more light enters the shadow, enhancing image resolution. Yet when reduced to near the wavelength scale, this introduces high-order diffraction, scattering light into distorted patterns and undermining performance. Traditional solutions use metasurfaces with nanostructures at sub-wavelength scales to suppress high-order diffraction. However, these systems face limits in spatial accuracy due to electromagnetic coupling between neighboring nanostructures.
Our alternative approach utilizes high-order diffraction rather than eliminating it. By manipulating scattered diffraction through a precisely calculated Fresnel zone distribution in flat lenses, we produce information-rich patterns. This method leverages large spatial frequencies propagated by high-order diffraction to reduce lateral focal size down to 0.44 λ, all without sub-wavelength features-significantly easing mass manufacturing. Experimentally, we have demonstrated center-to-center dry resolution of 190 nm, the highest reported among visible-light confocal microscopies, and achieved direct-writing resolution of 400 nm (0.385 λ) using laser-ablation lithography ["High-order diffraction for optical superfocusing," Nature Communications, Sep 6, 2024, https://doi.org/10.1038/s41467-024-52256-y].
The critical remaining challenge is operating this confocal system while moving samples with nanometer precision. Nanometer-scale vibrations, inherent to nearly all environments, limit accuracy. To address this, we developed specially fabricated components compatible with standard hardware that suppress these vibrations from over 100 nm to less than 3 nm on all axes. This breakthrough has enabled us to perform 3D scans of samples with unprecedented resolution and precision, establishing a new performance benchmark for confocal microscopy.