Fig. 1. Experiment setup. WDM, wavelength division multiplexer.

Fig. 2. Beat note frequencies versus linear polarization orientations of the pump.

Fig. 3. Beat note frequency versus pump polarization states for pumping at 980 nm.

Fig. 4. Beat note power variation for different pump polarization states for pumping at 980 nm.

Fig. 5. Beat note frequency variation for sequential pumping at different wavelengths.