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Mid infrared laser technology centered around 10pm has been driven by the availability of highly efficient, high power tunable CO2 lasers, continuously tunable lead salt diode lasers, and the rapidly advancing infrared fiber technology. Utilization of such systems is already becoming commonplace in medicine and laser heterodyne spectroscopic systems for remote sensing. These applications are increasingly requiring system flexibility, mobility, hence compaction and integration. To meet these needs, some steps toward 10 pm system integration and compaction have been explored with available mid IR components. We will report on our studies in the CO, laser + metallic piping/fiber + detector system and the tunable diode laser (TDL) + fiber detector system for heterodyning. Metallic piping will be compatible with w/g CO2 laser and w/g packaged detectors, where the 1.f. beat will be in the microwave region. Fibers will be compatible with TDL for direct butting, but incompatible with w/g packaged detectors. There is also severe thermal gradient between fiber section in the TDL coldhead at LH2 or LN2 temperatures, and section at room temperature. Current technology provides lowloss, rugged, near single mode piping, but appreciably higher loss, fragile, chemically unstable multimode fibers. However, there is no doubt fibers will be the ultimate mid IR laser system integration medium, so most of our efforts are in fiber testing and fiber system integration. Comparison studies have been done on relevent fiber parameters, such as loss, toxicity, hygroscopicity, refractive index, flexibility, shelf life, and thermal behavior at low temperatures of crystalline KRS-S, halide and chalcogenide glass fibers. Emphasis is placed on thermal shock evaluation at LN2 and LH2 temperatures with respect to mode structure, flexibility and shelf life.
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