Study on the dynamics of a gain spectral hole in silica-based erbium-doped fiber at 77 K

A study on the dynamics of gain spectral hole burning (GSHB) in a silica-based erbium-doped fiber amplifier at 77 K was performed. When a saturation signal was input into an Er3+-doped fiber, a multigain spectral hole structure that consisted of nine gain spectral holes, was observed in the wavelength region from 1510 to 1640 nm at 77 K. As for the Er3+ ion concentration dependence of these gain spectral holes, the depth of the gain spectral hole at around 1530 nm was found to become shallower in the silica-based erbium-doped fiber that had higher Er3+ ion content. This Er3+ ion concentration dependence of the gain spectral hole depth suggests that the contribution of the energy-transfer interaction between Er3+ ions excited to the Stark levels within the ^4 I_13/2 manifold plays an important role in the gain spectral hole formation at 77 K. As far as we know, this is the first report of the Er3+ ion concentration effect on the GSHB in the Er3+-doped fiber. The dynamics of GSHB is discussed in relation to the effect of energy transfer between Er3+ ions. In addition, the relation between gain spectral hole structure and the Stark energy structure of Er3+ ion is also discussed.