Centimeter-scale Yb-free heavily Er-doped silica fiber laser

The laser behavior of a centimeter-scale Er³⁺/Al³⁺ codoped silica fiber with core numerical aperture and core diameter of 0.15 and 8 μm, respectively, is reported. The core glass was prepared by the sol-gel method combined with high-temperature sintering; it contained Er³⁺ ion concentration as high as 1.32×10²⁰  ions/cm³ and an Al/Er mole ratio of 10. The high doping homogeneity of Er³⁺ ions in the fiber core was confirmed by an electron probe microanalyzer element scanning, long Er³⁺:  I_13/24 emission lifetime of 11.4 ms, and low refractive index fluctuation of fiber core (±1×10^-4). The signal gain of fibers with 4.6 cm, 10 cm, and 16 cm lengths was tested in the 1500-1620 nm range. A gain of 7 dB is achieved at 1560 nm in a 16-cm-long EDF under 230 mW pump power. Aimed for CO₂ sensor application, the laser behavior of Er/Al codoped fiber was tested at 1572 nm. A slope efficiency of 12% and an output power of 15 mW were achieved in a 10-cm-long fiber under 166 mW absorbed pump power. The newly developed silica fiber is promising for use in high-repetition-rate lasers.