A Self-Shielded Optical Nanoantenna probe for Sub-Diffraction Confinement in Optical Trapping, Imaging, and Quantum sensing Applications

This work introduces a self-shielded optical nanoantenna probe designed for sub-diffraction confinement and multifunctional nanophotonics applications. Our approach utilizes a simplified wet chemical etching process to create a wedge-shaped aperture in a a photosensitive single‑mode optical fiber, yielding a robust, compact, and cost-effective platform for advanced optical manipulation and quantum sensing applications. The wedge geometry controls the formation of a high-intensity annular region with a well-defined low-intensity center, desirable for optical trapping, biosensing, high-resolution imaging, and the potential excitation of quantum emitters, such as nitrogen vacancy (NV) centers in diamonds. Furthermore, placing a microsphere in the nanoantenna’s vicinity can enable the generation of a classical photonics nanojet alongside the non-diffracting bottle beam, thereby offering additional functionality and control for a range of multimodal applications. Our results show that this wedge-tipped nanoantenna maintains strong field confinement, with a spot size and depth of field comparable to those of previously reported microsphere-assisted nanojets, while retaining greater robustness, reproducibility, and ease of fabrication. The ability to generate both non-diffracting bottle beams and enhanced nanojets using a single platform paves the way for developing integrated nanophotonics, optical tweezers, high-resolution imaging, biosensing technologies, and platforms for investigating light–matter interactions with nitrogen vacancy (NV) color centers in diamonds and other materials.