Sapphire optical fibers for the delivery of Erbium:YAG laser energy

Single-crystal sapphire fibers are produced by the Saphikon edge-defined, film-fed growth (EFG TM ) technique. Total losses below 3 dB/meter have been measured at the Erbium:YAG laser wavelength of 2.94 microns. Fibers with lengths greater than a meter have delivered over 400 mJ of Er:YAG laser energy. EFG fibers have been shown to lose less than 10% transmission when bent to a 6 cm radius. The apparent numerical aperture (NA) has been measured as 0.31 for an unclad fiber, and 0.38 for fiber clad with teflon FEP. Scattering losses were shown to dominate loss, with measurements at both visible and 3 micron wavelengths using integrating spheres. Spectroscopy was used to identify absorptive losses in the EFG fibers.