Fiber-delivery system for high-power UV-A lightsources

For medical and analytical applications, thick-core fibers are widely spread. For special applications in the UV-A region, flexible and inexpensive fibers with high transmission in this wavelength region are required. On the other hand, new high-power UV-A light sources (LEDs, laser-diodes) are available in this wavelength region. Although silica-based UV-fibers are mainly used over the full UV-range, there are two additional candidates for the UV-A region: the Polymer Optical Fiber (POF) and the Polymer Clad Silica Fiber (PCSF). Especially, the higher flexibility of the thick-core POF is superior in comparison to silica fibers with the same outer diameter. However, UV-induced losses exist in these fibers, too, using UV-light sources with significant power below 350 nm wavelength. However, the UV-damage with UV-light above this wavelength is significantly reduced; test results with high-power 365 nm UV-LED and 375 nm laserdiodes will be shown and discussed. On the other hand, the entire fiber-optic system, including the light-source, will be characterized. Especially the coupling efficiency between the light-source and the fibers was studied theoretically and experimentally.