Efficient amplification using the super(4)F sub(3)2/ arrow right super(4)I sub(9)2/ transition in Nd-doped silica fiber

Amplification characteristics of the three-level super(4)F sub(3)2/ arrow right super(4)I sub(9)2/ transition in Nd-doped silica glass fiber are investigated under strong signal saturation and high pump power (150 mW). Aluminum codoped Nd-silica fibers exhibit strong superfluorescent behavior in the four-level super(4)F sub(3)2/ arrow right super(4)I sub(11)2/ transition which limits the optical conversion efficiency into the three-level transition. Ge-doped silica fibers do not exhibit this limitation and can efficiently amplify in the three-level transition with current laser-diode pump technology.