Double-clad Cr4+:YAG crystal fiber amplifier.

A novel double-clad Cr4+:YAG crystal fiber is demonstrated by use of a codrawing laser-heated pedestal growth method. Up to 10 dB of gross gain at a wavelength of 1.52 microm is achieved at a pump power of 0.83 W, which, to our knowledge, is the first Cr4+-doped fiber amplifier in the optical fiber communication band.