Defect orientation models of germanosilicate photosensitivity:paradoxical observations

摘要

Single-photon photodarkening of a germanosilicate optical fiber preform is reported and discussed in the context of oxygen deficiency defects. Qualitative and semi-quantitative aspects of a multiphoton interference model of photorefractive change in germanosilicate fibers are explored. The conditioning of production of yellow Cerenkov radiation by a fiber is reported and attributed to homogeneously induced $chi$+(2)$/ susceptibility. Two nonlinear processes are again thought to be involved. The need for mode detuning to take full advantage of waveguide nonlinear effects is highlighted.