Realizing high adjustability of bandwidth and energy of output pulse in a self-similar femtosecond fiber laser

•High adjustability in energy and bandwidth of self-similar femtosecond fiber laser.•Investigation the impact of key cavity parameters on spectral bandwidth and energy.•The optimal output coupling rate of 0.5/0.1 for the maximum energy/ bandwidth.•The larger compressor negative GVD for broader bandwidth and higher pulse energy.•The maximum variation ranges of Net GVD for modulation depth of 0.04.•The optimal value of Net GVD of 0.015 ps2 for the broadest adjustability range. Numerical solving of nonlinear Schrödinger equation is performed for a self-similar femtosecond fiber laser cavity in order to investigate the effect of its key parameters (e.g., output coupling rate, net dispersion of cavity, and modulation depth) on the energy and the spectral bandwidth of output pulse in the stable mode-locking state. The calculations indicate that by decreasing the output coupling rate from 0.8 to 0.1, the output pulse bandwidth increases while the maximum output energy can be achieved for the output coupling rate value of about 0.5. On the other hand, the decrease in net cavity dispersion due to the increase of negative GVD of the pulse compressor will increase the bandwidth and energy of the output pulse. Finally, the optimal net cavity dispersion is determined for which the widest adjustment range of modulation depth is obtained; this leads to a broad adjustability range for energy and spectral bandwidth of the output pulse. Then, the design and fabrication of a self-similar femtosecond fiber laser with a high adjustability range for bandwidth and energy of output pulse is realized according to the simulation results.