Analysis of a 1060-nm Nd:SiO2 superfluorescent fiber laser

This CW source is made of a single-mode Nd-doped silica fiber end-pumped near 830 nm by a dye laser, with a thin high reflector placed against its input end for enhanced conversion. At the maximum output power of 13 mW, obtained with a pump power of 75 mW, the emission linewidth is still as broad as 16 nm, and the pump-to-signal conversion efficiency approaches the quantum limit of 78%. A simple model of superfluorescence in fibers, which relates the source emission characteristics to the fiber single-pass gain, is also presented. The single-pass gain, measured to be 0.27 dB/mW, was used to fit the model to the data. A good agreement is found for the nonlinear output versus input power curves of the sources, but it appears that the emission linewidth does not narrow with increasing pump power as fast as expected. Based on these results and an existing model of gain in single-mode fibers, it is suggested that simple improvements in the fiber design may reduce the pump requirement of this source and make laser-diode pumping possible