Lasers erbium-doped crystals

Erbium-doped yttrium-aluminum-garnet, a crystal used for lasers. It lases at a fundamental wavelength of 2.94 gm. 

Glass fibers, up to 0.5 m in length and 5 to 30 jjm in diameter were pulled from the apparatus at rates of 1.0-1.5 m/s before crystallization terminated the process. The fibers had a homogeneous appearance and smooth surfaces. They were transparent, highly flexible, and x-ray amorphous. Glass fibers of this kind, which were also made from erbium- or neodynium-doped yttria alumina compositions, would therefore expand the range of fiber lasers into the mid-infrared. 

---