Compact Yb-doped mode-locked fiber laser with only one polarized beam splitter.

We experimentally demonstrate a kind of simplified Yb-doped mode-locked fiber laser with a nonlinear polarization rotation technique. In the oscillator, there are no waveplates, physical bandpass filters, or polarization controlling devices except for one polarized beam splitter and a polarization-independent isolator. In the experiment, self-started stable mode locking pulse trains are obtained with four different cavity lengths: 110 m, 66 m, 50 m, and 26 m. To make clear the mechanism of pulse formation of this kind of simplified fiber laser, the characteristics of which are called an artificial saturable absorber, are discussed and the influences of these parameters on mode locking are also analyzed.