2 μm bright-dark pulses in Tm-doped fiber ring laser with net anomalous dispersion

We demonstrate bright-dark pulses near 2 mu m in a Tm-doped fiber laser (TDFL) for the first time. Bright-dark pulses could be achieved when the laser works in the passively mode-locking regime and the net group velocity dispersion is quite anomalous. A polarization controller is employed to manipulate the polarization states of the laser oscillation modes. The dark and bright pulses are confirmed to be two orthogonal linear polarization components that are coupled incoherently in the laser cavity. Experimental results also show that the dark and bright pulses have different spectral distributions. (C) 2014 The Japan Society of Applied Physics