Polarization-locked temporal vector solitons in a fiber laser: experiment

We experimentally observe polarization-locked vector solitons in a passivel y mode-locked fiber laser. The vector soliton pulse is composed of componen ts along both principal polarization axes of the linearly birefringent lase r cavity. For certain values of birefringence and pulse energy these compon ents propagate with a constant relative optical phase of +/- pi/2, and henc e the pulse has a fixed elliptical polarization state. The linear birefring ence of the cavity is canceled by the nonlinear birefringence created by th e unequal amplitudes of the two polarization components. This dynamic equal ization of the phase velocities of the components results in the stable pro pagation of an elliptically polarized vector soliton pulse. Under different conditions we also observe the nonlinear instability of the fast principal axis as an intracavity pulse linearly polarized along the slow axis of the cavity. We present the experimental characterization of both the polarizat ion-locked vector soliton and the fast axis instability and discuss the non linear mechanism creating both phenomena. (C) 2000 Optical Society of Ameri ca [S0740-3224(00)01003-1] OCIS codes: 060.5530, 190.4370, 140.4050, 320.70 90, 140.3500.