Micro-needle-dispenser-based direct writing of optical microlenses on optical fiber facets for visible-range applications

This study presents a droplet-based micro-dispensing technique for the fabrication of photopolymer microlenses directly on the end facets of optical single-mode fibers. The process is based on a layer-by-layer droplet stacking approach, where each deposited droplet is individually cured with ultraviolet light to achieve precise control over the microlens height, curvature, and geometry. In contrast to traditional fabrication techniques, this method removes the need for lithographic or molding processes and allows rapid and customizable fabrication. Finite-Difference Time-Domain (FDTD)-based optical simulations agree with the experimental results, confirming accurate control over the beam shaping properties of the fabricated lenses. A focal beam radius down to approximately 1.7 μm with a working distance of 38 μm at a wavelength of 635 nm has been achieved. This facilitates potential applications e.g. where coupling from single-mode fibers to photonic chips with smaller mode field diameter (MFD) is required. The developed approach provides a scalable method for directly integrating microlenses into photonic integrated circuits and other optical platforms for sensing, imaging, and biomedical single-fiber probing applications.