A fiber optic system for water analysis with high transparency in the deep-UV region (lambda >/= 190 nm) is presented. The system consists of special UV-improved silica fibers and a liquid-core waveguide (LCW) as an optical cell. The apertures of both light guides, the silica fiber and the LCW, are matched. The optical losses of the device are investigated experimentally and compared with theory, especially with a standard free-space geometry. The performance of the system with respect to UV absorption spectroscopy is demonstrated for nitrate and chlorine pollution in pure water. For a 203-mm-long LCW the detection limits have been determined to be as low as 22 mug/L for nitrate and 26 mug/L for chlorine.

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There are different types of optical capillary cells in use for the modern on-line UV-VIS analysis of liquids using fibre spectrometers. These cells have the advantages of low sample volume, long optical pathlengths and compatibility to fibre optics. In this paper, we will show that the liquid core waveguide (LCW) is a particularly useful device because the light intensity is confined in the liquid core. This is shown in two ways. Firstly, the measured total optical losses of the LCW capillary device indicate typical guiding losses less than 3 dB m-1 without a significant dependence on either fibre diameter or on the diameter of the capillary. Secondly, measurements of the radial intensity distribution exhibit a clear maximum in the core in the case of the LCW device. The efficiency of a liquid core waveguiding cell is investigated for different core diameters (0.3-4 mm) in combination with different coupling fibre diameters (200-600 µm). A thin cell with a 360 µm diameter with a sample volume in the µl range and low coupling losses will be discussed as well.

During the last years we developed a flexible beam guiding system for DUV-laser radiation (? 193 nm, 213 nm). This laser scalpel is based on hollow core waveguides and special fused silica optical fibers. We were able to demonstrate the feasibility of the laser scalpel to ablate biological tissues and technological materials. Our current interest is to develop a thinner scalpel tip which consists of200 im optical fibers instead of 600 tm fibers. The performance of these thin fibers was evaluated . We developed a computer controlled measurement system to study the optical fiber performance in dependence on laser fluence, laser intensity, laser repetition rate and fiber coupling conditions. We also investigated the long term behaviour ofthe modified optical fibers for the laser scalpel.

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