High-energy quasi-trapezoid noise-like pulse generation and harmonic operation in a fiber laser.

We report on the observation of quasi-trapezoid noise-like pulses (NLPs) in a fiber laser with a large anomalous dispersion regime based on nonlinear polarization rotation. Trapezoidal NLPs operate at 1568 nm with a fundamental repetition rate of 946.14 kHz. The pulse width can widen from 12.54 to 32.17 ns, and the pulse energy can be increased from 8.81 to 25.84 nJ by increasing the pump power from 77.4 to 244.4 mW. The maximum intracavity energy of a trapezoidal pulse can reach ~258.4 nJ. Furthermore, stable high-order harmonics are obtained by regulating the pump power and polarization state. In the harmonic mode-locking regime, the second- to the tenth-order harmonic trapezoidal pulses can be achieved in the fiber laser. [ABSTRACT FROM AUTHOR]