Er 3+-doped phosphate glasses for fiber amplifiers with high gain per unit length

Abstract

The effect of the types of alkaline earth metal ions (Mg 2+, Ca 2+ and Ba 2+) and concentration of Al 2O 3 and BaO on the refractive index and the effective emission linewidths of the 4I 13/2− 4I 15/2 transition of Er 3+ ions in phosphate glasses, 64P 2O 5 · 12Al 2O 3 · 3.5( Er 2 O 3+ La 2 O 3)·20.5 MO ( M= Mg, Ca, Ba) and 64P 2O 5 · 3.5(Er 2O 3+La 2O 3) · (21.5 − x)Al 2O 3 · (11+x) BaO (x=0,3.5,6.5 and 9.5) , were investigated. A single mode Er 3+ doped phosphate glass fiber with a core diameter of 4 μm was fabricated by the rod-in-tube technique. A new Er 3+ doped fiber amplifier is demonstrated pumping with a 980 nm fiber pigtailed-laser diode. A gain per unit length greater than 2 dB/cm is demonstrated, which is the largest gain per unit length for fiber amplifiers to our knowledge.