Passive mode locking of fiber lasers upon doubling the period of repetition of ultrashort pulses in the output radiation

The dynamics of the output radiation of fiber lasers with nonlinear losses caused by an intracavity polarizer and by nonlinear optical activity due to the Kerr nonlinearity of the fiber is studied by numerical simulation. It is shown that the model of lasing that takes into account the concentration of nonlinear losses in the intracavity polarizer describes the characteristic transient regimes of the passive mode locking, connected with a nonstationarity of the parameters of the output radiation: doubling of the period of repetition of the field structure in the output radiation, appearance of slow periodic changes of the parameters of light pulses in the regimes with the doubled period, and transitions to the regimes with chaotic change of the characteristics of ultrashort pulses.