Study on self-pulsing dynamics in Yb-doped photonic crystal fiber laser

• Self-pulsing dynamics is studied in Yb-doped photonic crystal fiber laser.
• In double end pumping configuration self-pulsing is reduced at high pump powers.
• Rate equations were solved without feed back from the mirrors in the cavity.
• Non-uniform distribution of single-pass upper level population along fiber length.
• Weakly pumped part of fiber causes “saturable absorption” and hence pulsing.

In this paper, we present the experimental and analytical study of self-pulsing dynamics in Yb-doped photonic crystal fiber laser in single-end and double-end pumping configurations. It has been found that the intensity of self-pulses is considerably higher in the single-end pumping configuration as compared to that for double-end pumping configuration. In both the cases, it was noted that when the pump power was sufficiently high, intensity and occurrence of the self-pulses were reduced. However, the reduction in the intensity of self-pulses was significant in the double-end pumping. Experimental study shows that occurrence of self-pulses is due to the initial relaxation oscillations and re-absorption and there is no role of nonlinear phenomena in the generation of self-pulses. The rate equation analysis shows that the non-uniformity in single pass distribution of upper level population along the fiber length is responsible for re-absorption and hence self-pulsing. In the case of single-end pumping, single pass distribution of upper level population along the fiber length has more non-uniformity as compared to the double-end pumping, and hence stronger self-pulsing is observed.