Possibilities and limitations of optical fibers for the transmission of excimer laser radiation

For fiber-delivery systems with UV-lasers the candidates are mainly optical fibers with an undoped high-OH silica core and a F-doped silica cladding. However, there re there important limits to UV-applications: surface damage, two- photon-absorption and defect-generation during operation. In the last two years, UV-improved fibers with significantly reduced defects have been developed. This improvement is most pronounced at 248 and 193 nm, because at these critical wavelengths the induced losses are strongly influences by the main broadband UV-defects with absorption maxima at 165 nm and 215 nm. We will summarize the results including the influence of the main parameters. In addition, the transmission capacity for the 308 nm wavelength is of interest due to medical and industrial applications. At this wavelength the influence of the nonlinearities is much lower; however, the induced losses in standard fibers are still an important factor. To show the advantages of the UV- improved fibers, the transmission characteristics at 308 nm wavelength will be described in more detail, for the first time.