The peak power of pump pulse is a key factor in the generation of supercontinuum source. Observably, as the peak power of the pump pulse increases, the spectral range of the supercontinuum becomes wider. In order to study the blue shift limit of PCF fiber at different peak powers, in our experiment, the change in peak power is achieved by introducing a different length of chirped fiber after the oscillator to vary the pulse width. The pump source is a self-made laser with pulse duration, operating wavelength and repetition rate of 12 ps, 1064 nm and 68 MHz, respectively, which are injected into the photonic crystal fiber after three stages of amplification. Finally, a supercontinuum with an average power of 358 W in the spectral range of 466 nm to 2400 nm was achieved. Experiments have shown that the introduction of large positive chirp has a significant effect on the supercontinuum of the 10 W class, but for a supercontinuum with a sufficiently high average power (over 100 W level supercontinuum spectrum). after the peak power threshold is exceeded, further blue shift of the spectrum cannot be achieved by increasing the peak power, but the high peak power helps to improve the spectral flatness of the supercontinuum. The four-wave mixing, dispersive wave generation, radiation trapping with the soliton play much important role in the blue-shift of SC spectrum, but the short-wave edge is limited by the group velocity matching condition, which is determined by the dispersion characteristics of the PCF, not only peak power of the pump pulse. In order to further extend the short-wave spectrum, other methods are required, for example, changing the structural characteristic of the PCF, etc.
Thulium-doped fiber laser is one of the most promising high power mid-infrared sources which attracts lots of attention recently. However, there is no comprehensive theoretical model which can be used for precise simulation of the performance of the pulsed Thulium-doped fiber laser. A combined theoretical model is proposed in this work by integrating the laser rate equation and Ginzburg-Landau equation into the iteration process. Good agreement between the experiments and simulations is achieved in a Thulium-doped fiber amplifier employing counter-pumping scheme.