Pulling Doped-YAG Single-crystal Fibers

Pulling bulk crystal into fiber is suitable for §dvice applications in optical communications because §of its structural similarity to silica fiber. Among §fiber growth techniques, the laser-heated pedestal §growth method (LHPG) was adopted. It is crucible §free and can therefore produce high-quality single §crystals. However, interface loss of the fiber is §one of the main causes of optical loss. In order to §reduce the loss, a proper method to clad the fiber §is important for high performance device. For laser §application, high-efficient Nd:YAG lasers were §demonstrated using gradient-index crystal fibers. §For ASE and optical amplifier applications, Cr4+:YAG §crystal fiber was studied due to its fluorescence §just covering the low loss window of optical fiber. §To reduce the fiber diameter and propagation loss, a §novel cladding technique, codrawing LHPG, was §developed. A double-clad fiber was successfully §grown by the technique. As much as 2.36 mW of ASE §with a bandwidth of 265 nm was demonstrated. Up to §16-dB of gross gain at 1470 nm was also achieved. It §is the first transition metal-doped fiber amplifier §in the optical communication band.