Experimental Investigation of Ultrafast Yb:fiber Oscillators Based on Several Dominant Mode Locking Methods

To find out which kind of mode-locked fiber oscillator is superior, six kinds of typical mode-locked Yb:fiber oscillators, including nonlinear polarization evolution (NPE)-based oscillators (i.e. conventional NPE-based oscillator, polarization maintaining (PM) NPE-based oscillator), nonlinear amplifying loop mirror (NALM)-based oscillators (i.e. figure-8 oscillator, all-fiber figure-9 oscillator, free-space figure-9 oscillator), and semiconductor saturable absorption mirror (SESAM)-based oscillator, were presented and crosswise compared. Except for the conventional NPE-based one, all the others were constructed with all-PM fiber components. Experimentally, detailed crosswise comparisons were carried out quantitatively and qualitatively for different oscillators in terms of spectral bandwidth, spectral shape, pulse repetition rate, signal-to-noise ratio (SNR), mode-locking threshold, self-starting mode-locking pump power, robustness, component life, construction simplicity, and so on. In addition, subjective sensations on each oscillator were also provided, which could be helpful for decision-making when one wants to make or purchase an oscillator. Finally, the all-fiber figure-9 oscillator was suggested to be the best choice even it needs higher pumping power, which could be an ideal seed for high power ultrafast laser amplifiers.

Automated summary

The study presents a comparison of six typical mode-locked fiber oscillators and suggests the all-fiber figure-9 oscillator as the best choice for high power ultrafast laser amplifiers, despite the need for higher pumping power.