Unidirectional lasing using loss management in a reciprocal fiber ring laser

We report on the observation of a new phenomenon, occurring in a fiber ring laser. This phenomenon describes the transition from an initially bidirectional emission of a reciprocal fiber ring laser to a unidirectional emission at a certain pump power threshold. In addition, the final direction is not predefined but appears to be randomly chosen every time the threshold is exceeded. Therefore, we term this new phenomenon as direction instability. In addition we provide a first discussion of how the pump power threshold and the final direction can be influenced by the length and the loss of the cavity.