Spatial Beam Intensity Shaping Based on an On-Fiber 3D Nanoprinted Microlens

Micro- and nano-sized optical elements have been widely explored for various applications, including telecommunications, sensing technologies, and laser processing. The “center beam-in-ring” beam configuration is promising in laser cutting and welding to avoid spatter of particles or droplets, and it holds potential applications in medical treatment. In this study we propose a dot-in-ring and a ring-in-ring beam shaping microlens fabricated on the tip of an optical fiber. These microlenses, featuring freeform light output surface designs, were fabricated on cleaved fiber ends using femtosecond laser-induced two-photon polymerization (TPP) 3D printing. Both simulations and experimental results confirm that the proposed fiber-tip microlenses effectively convert the Gaussian beam from a single-mode fiber into a dot-in-ring beam and a ring-in-ring beam, while maintaining excellent optical field propagation and energy distribution over a defined distance. This work highlights the capability of TPP 3D printing as a powerful tool for integrating micro-scale beam shaping elements onto optical fibers, enabling the development of compact devices.