Generation of 6.5-W linearly polarized sub-100-fs pulse with a compact Yb-doped photonic crystal fiber amplifier

High-quality, ultrafast fiber lasers have long been favored by both research and industry for many desirable properties. Here, we present an Yb-doped fiber laser system by utilizing a directly spliced photonic crystal fiber to amplify a seed source, and sub-100 fs ultrashort pulses are obtained with an average power of 6.55 W and at a repetition rate of 100.15 MHz. The M2 factors are measured to be about M_x^2=1.13 an M_y^2=1.12, respectively. The standard deviation of output power over a 2.5-hour period is determined to be 0.72 % and no significant wavelength drifts or intensity fluctuations are observed. These results demonstrate the promising potential of this compact fiber laser system for both research and industrial applications.