The Er:YAG laser-induced damage (LID) threshold and modal properties of single-crystal sapphire fibers grown by the laser-heated pedestal-growth method have been measured. The lowest loss (∼0.4-dB/m) sapphire fibers produce little mode mixing and therefore deliver a near-single-mode output profile if the Er:YAG laser input beam profile is also nearly Gaussian. Normally, however, Er:YAG laser output beam profiles are multimode with numerous high-energy spikes. This leads not only to a multimode output from the fiber but also increased fiber loss that is due to higher-order mode coupling. The results of LID testing give a damage fluence of ∼1.4 kJ/cm2 for 300-μm core-only sapphire fibers at 2.94 μm.
© 1998 Optical Society of AmericaFull Article | PDF Article
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