Optical Focusing beyond the Diffraction Limit via Vortex-Assisted Transient Microlenses

Focusing light beyond the diffraction limit is among the greatest challenges in optical sciences, which would revolutionize many optical technologies from imaging and optical trapping to light delivery and photomedicine. To achieve subdiffraction focusing, metamaterials, materials with engineered scattering properties, or attached microspheres have been proposed. Here we introduce a new paradigm to achieve a physical focus beyond the diffraction limit without additional optical elements or exogenous labels, but only using light–matter interactions. We spatially control light absorption within the focal region of a lens to generate a transient heat source and sculpt a semiparabolic refractive index pattern within the sample itself. This effectively generates a converging microlens with a focusing spot below the diffraction limit of the optical system that can be used for super-resolution imaging by scanning the spot across the sample. Our method is broadly compatible with imaging and focusing systems used in many applications.