Nonlinear Polarization Evolution Influence on Pump-Induced Repetition Frequency Dynamics in Hybridly Mode-Locked Erbium Fiber Laser

Erbium-doped mode-locked fiber lasers emitting ultra-short pulses (USP) of pico- and femtosecond durations are well-elaborated commercially available devices offering great flexibility in design, regimes of operation and output characteristics. These sources usually referred to as frequency combs are widely employed in different fields of science and industry. However, many efforts have been already put on comb stabilization systems development as well as understanding their potential stability limitations, while less activity is aimed to study fundamental principles standing for repetition (f) and carrier-to-envelope offset (f_ceo) response behaviour upon different perturbations such as pump power or temperature variations. Recently, a theory of femtosecond frequency comb from an Erbium fiber laser has been proposed [3] identifying a number of physical mechanisms including spectral shift, third-order dispersion (TOD), resonant gain, self-steepening (SS) and chirp-assisted frequency dependent loss (FDL) responsible for pump-induced changes in pulse repetition frequency. In this work, we have shown for the first time a decisive contribution from Nonlinear Polarization Evolution (NPE) mode-locking mechanism to pump-induced repetition frequency response dynamics via frequency dependent loss term in the stretched-pulse Erbium-doped all-fiber ring oscillator with distributed polarizer.