Silver halide optical fibers were used as attenuated total reflection elements for infrared evanescent wave spectroscopy of gases in liquids. The evanescent wave absorption spectra of chlorodifluoromethane (Freon-22) and carbon dioxide gases (CO2) in water were studied and the dependence on vapor pressure of the gas and temperature was investigated. Absorption peaks were easily traced and correlated well with those in the literature. The use of the infrared (IR) fibers in the fiberoptic evanescent wave spectroscopy system bypasses the difficulty of ordinary IR spectroscopy related to the strong IR absorption of most liquid solvents, and provides a flexible, easy, and inexpensive way of determining the presence and concentration of gases in liquids to within about 5% accuracy.
Laser welding has been used for connecting various tissues in the body. In urology such welding has the advantage of forming an immediate water tight seal. We have developed a fiberoptic system that makes it possible to monitor and control the temperature of the tissue during welding. In previous work we demonstrated that this system could be successfully used to weld punctures in the urinary bladder of rats. It was found that optimal welding was obtained at a temperature of 55°C. In this work we used the same system for welding of large openings (cystotomy) in the urinary bladder of rats. In early experiments we used stay sutures and decompressing catheters. It was later found that complete closure can be obtained with C02-laser welding alone. This work demonstrates the feasibility of using temperature controlled laser welding as an efficient surgical tool.
A noncontact laser calorimetric method for low absorption-coefficient measurements of various optical materials is proposed. For temperature monitoring of the samples, silver halide fiber radiometry is utilized. The capability of this technique is demonstrated by the measurement of the absorption coefficients of fused-quartz rods at 500 nm (Ar laser radiation) and of mixed silver halide crystals and fibers at 10.6 µ;m (CO(2) laser radiation). Good agreement with ordinary laser calorimetry is obtained.
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