405 nm diode laser system for curing UV adhesives based on embedded sidelight-activated polymer optical fibers

Within this work, an optical system was developed for coupling 405 nm laser radiation into a bundle of polymer optical fibers (POF) for a UV curing application. Traditional UV curing methods require at least one transparent joining partner, which limits their use in certain industrial applications. To enable efficient light coupling even between non-transparent materials, a novel bonding process has been developed that uses sidelight activated POF woven into a fabric. By lateral emission from the fabric, the radiation reaches the bonding zone, so that the adhesive is cured over a large area. The optical system aims to achieve homogeneous illumination in the bonding zone by employing a diode laser, which offers advantages over traditional LED sources, particularly in terms of absorption efficiency of UV adhesives. The system is characterized by its coupling efficiency and the feasible homogeneity of the intensity profile in the image plane. Both quantities have been determined experimentally and by simulation with Zemax OpticStudio, achieving a coupling efficiency of up to 74% and a homogeneity exceeding 95% in the focal plane. Further investigation into the distribution of defects inside the fiber revealed that specific parameters significantly influence the homogeneity of lateral light emission. The results indicate that a tailored defect configuration can optimize the curing process, paving the way for future applications in industrial adhesive bonding. The findings underscore the potential for commercialization of this innovative optical coupling system within manufacturing sectors requiring efficient and large-area UV curing solutions.