The integration of single atoms with photonic integrated circuits promises scalable quantum information platforms, yet a fundamental challenge of trapping atoms into the near-field interaction region of the waveguide mode remains. Here we propose an on-chip waveguide-based nanolens, designed to focus a free-space incident Gaussian beam, thereby creating a tight optical beam directly above the waveguide surface. In contrast to treating the diffraction effect of the on-chip nanostructure as detrimental, our approach can utilize the effect to realize precise near-field positioning and trapping of single atoms, which allows strong coupling between the trapped atom and the guided photons in the waveguide. Through numerical simulation, we demonstrate that for a free-space input of an 852-nm Gaussian beam with a waist of $1\mu \mathrm{m}$, a waveguide can generate a near-field focused beam with a waist of only $0.66\mu \mathrm{m}$ and a height of about $0.07\mu \mathrm{m}$ above the waveguide surface, featuring a 3.0-mK dipole trap with only 3.5-mW free-space trap laser power assisted by a blue-detuned waveguide mode. The increase of atomic spontaneous emission rate induced by near-field atom-waveguide mode coupling is analyzed by the Purcell factor, which is up to $3.1\times {10}^{-3}$. Furthermore, it is demonstrated that the cold atoms can be transported from the trap center of the nanolens to the optical trap arrays created by the evanescent field of the waveguide modes. Our proposal provides a scalable approach for realizing a near-field waveguide-integrated single-atom array, paving the way toward hybrid photonic-atomic circuits for quantum applications.

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• Atom & ion trapping & guiding
• Spontaneous emission
• Stark effect