Rare-earth doped single-crystal (SC) Yttrium Aluminum Garnet (YAG) fibers are excellent candidates for high power lasers. These SC fiber optics combine the favorable low Stimulated Brillouin Scattering (SBS) gain coefficient and excellent thermal properties to make them an attractive alternative to glass fiber lasers and amplifiers. Various rare-earth doped SC fibers have been grown using the laser heated pedestal growth (LHPG) technique. Several cladding methods, including in-situ and post-growth cladding techniques, are discussed in this paper. A rod-in-tube approach has been used by to grow a fiber with an Erbium doped SC YAG fiber core inserted in a SC YAG tube. The result is a radial gradient in the distribution of rare-earth ions. Post cladding methods include sol-gel deposited polycrystalline.
Single crystal (SC) yttrium aluminum garnet (YAG, Y3Al5O12) as a host material has the ability to be doped with high
concentrations of Er3+ ions. We utilize this ability to grow a 50% Er3+ doped YAG SC fiber, which was inserted into
a SC YAG tube. This rod-in-tube was used as a preform in our laser-heated pedestal growth (LHPG) apparatus to
grow a fiber with a radial distribution of Er3+ ions. The work shows that there is a distribution of Er3+ ions from their
fluorescence and two different techniques were used to measure the index of refraction.