A fiber optic system for water analysis with high transparency in the deep-UV region (λ ≥ 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 μg/L for nitrate and 26 μg/L for chlorine.
© 1998 Optical Society of America
(060.2290) Fiber optics and optical communications : Fiber materials
(120.6200) Instrumentation, measurement, and metrology : Spectrometers and spectroscopic instrumentation
(230.7370) Optical devices : Waveguides
(280.0280) Remote sensing and sensors : Remote sensing and sensors
(300.6540) Spectroscopy : Spectroscopy, ultraviolet
Peter Dress, Mathias Belz, Karl F. Klein, Kenneth T. V. Grattan, and Hilmar Franke, "Water-Core Waveguide for Pollution Measurements in the Deep Ultraviolet," Appl. Opt. 37, 4991-4997 (1998)