The dependence of the filtering bandwidth on the mode locking technique was studied in details in two types of mode locked fiber laser cavities; one utilizes SESAM, while the other employs NPE. The results show that for the two cases, below certain value of filtering bandwidth, no mode locking can be observed and the cavities will be in a lossy region. Moreover, NPE-based all fiber cavities can support narrower spectral bandwidth compared to SESAM-based cavities. Hence, NPE-based cavities produce shorter pulse width than SESAM-based ones. Experimental investigation was carried out to verify our simulation results and good agreement was achieved.
An increase in energy of pulses generated in a similariton mode-locked femtosecond fiber laser is shown experimentally
by increasing the length while reducing the doping of the ytterbium-doped fiber gain medium. Mode-locking is achieved
by nonlinear polarization rotation evolution in a cavity using a combination of fiber and bulk optical components. The
level of doping of the gain medium is varied by using lengths of differently doped ytterbium fiber. Experimental results
verify that an increase in length of gain medium with a lower doping results in an increase in the output pulse energy.
We report on a novel simple configuration of an Yb-doped fiber laser cavity comprising only Yb-doped fiber and a
saturable absorber element. Numerical results show that stable mode-locked operation does exist in such a laser cavity
in limited range of parameters. The conditions to obtain stable pulses are investigated as a function of the Yb-fiber
bandwidth, length, and gain coefficient. The temporal and spectral behavior of the femtosecond pulses are also studied
for different input parameters. The instability dynamics of the mode-locked pulse is also elucidated.