Self-written micro-lenses on fiber tips: investigation of the material parameters and optical behaviour

Self-written waveguides (SWWs) are well investigated and established to create low-loss connections between different optical components, i.e. waveguides, fibers, light sources or detectors by local photopolymerization using UV-near light. However, the technique is not limited to create interconnects. In our work, the localized curing process was used to polymerize a small portion of a drop of photoresist on the tip of an optical fiber. Due to the surface tension, a lensed shape is formed at the end of the drop. This shape is preserved during the curing process and defines the geometry and thereby the focal length of the lens. The influence of different parameters such as material, layer thickness, curing time and power and the dilution of the photoresist and their effect towards the lens shape were investigated. Hereby, we were able to produce different kind of lenses on multi-mode fiber as well as on single-mode fiber tips. The corresponding focal-lengths were determined as well as the lens shapes to investigate if it is possible to control and predict the function and shape of the optical elements created.