Figure 2 | Scientific Reports

Figure 2

From: From instable directional switching to controlled unidirectional operation in a nonlinear fiber ring laser

Figure 2

Spectral evolution for the preferred counter clockwise direction at the entrance of the passive fiber with (a) no filter stage included in the cavity (broad spectrum with 6 Stokes orders prior to NUO), (b) filter stage constituted of WDMs 1–3 (a single Stokes peak prior to NUO and prevention of broadening of the laser wavelength), (c) WDMs 1–4 (SRS and NUO retardation to 12 W pump power). NUO is present in the upper parts of the figures accompanied by a much broader spectrum compared to bidirectional operation for lower pump powers. Note the different y-axes. The inset in (b,c) highlight SRS right below the NUO threshold. In (d) the Raman spectrum is shown at the threshold to lasing.

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