Doughnut beam shaping based on a 3D nanoprinted microlens on fiber tip

Spatial beam intensity shaping is of great significance in many applications, such as laser fabrication and medical treatment. In this study we present a new method for doughnut beam shaping based on 3D nanoprinted microlens on fiber tip. The optical structure of the microlens was first designed and optimized based on illumination optics in software, and then the microlens was fabricated on a single-mode-fiber tip by femtosecond laser induced two-photon polymerization. Both simulation and experiment results have demonstrated that the Gaussian beam output from a single-mode fiber can be successfully transferred to a high-quality doughnut beam by using the fiber-tip microlens. The proposed microlens shows larger tolerance in fabrication resolution compared with optical diffraction beam shaping elements. Our research shows that the femtosecond laser induced two-photon polymerization provides a new and flexible method for the integration of micro-scaled beam shaping elements on optical fibers.