Polarization-domain-wall complexes in fiber lasers

To study the possible build-up of polarization-domain-walls (PDWs) in fiber laser cavities, an erbium-doped fiber ring laser was used and a wide range of vector polarization dynamics that can be selected at a given pump power, by using the degrees of freedom of two intracavity polarization controllers (PC) was investigated. A simple theoretical model that explains polarization switching in fiber ring lasers featuring a normally dispersive cavity with a typical, moderate, level of birefringence is presented. Such polarization dynamics, based on a special class of polarization-domain-wall structures, agrees qualitatively well with experimental observations. The paper stresses on the complex and chaotic nature of the observed polarization-switching states. These complex dynamics are corroborated by detailed numerical simulations predicting the build-up of consecutive and transient PDW structures at the subnanosecond scale, which are not fully resolved experimentally.