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Frequency-Doubling In Glass Fibers

The recent observation of efficient second-harmonic generation in glass fibers is a very exciting result. Fibers containing a small amount of phosphorous (and germania) doping in the core, that undergo an optical "preparation" process show efficient frequency-doubling. In this paper, a review is presented of some of the most important experiments reported in the literature, as well as a critical discussion of the models existent at present to explain the processes involved.