Abstract
Based on the coupled Ginzburg-Landau equations and Jones matrices of the waveplates considered, a numerical model of an all-normal-dispersion fiber laser mode-locked by nonlinear polarization rotation has been proposed. The operating characteristics of the fiber laser discussed were studied numerically. It has been found that the proposed all-normal-dispersion mode-locked fiber laser (AND-MLFL) could deliver dissipative solitons (DSs) with a M-shaped and U-shaped spectrum, the splitting pulse with a divided spectrum and the amplifier similaritons. The evolution of the intra-cavity pulse and spectrum has been calculated under different regimes and the effects of group velocity dispersion (GVD) and nonlinearity are analyzed. When the fiber laser delivers DSs or causes pulse splitting, nonlinear effects dominate the pulse evolution. With the increase of the accumulated nonlinear phase shift, the operation states change from DS with a M-shaped spectrum to a U-shaped spectrum, and then to the splitting pulse. In the case of amplifier similaritons, both the GVD and nonlinearity play important roles in pulse evolution. The effect of nonlinear polarization rotation and filtering on the pulse reshaping has been analyzed. When the fiber laser delivers DSs with a M-shaped spectrum, the filter has a very weak effect on the pulse and on spectral reshaping. However, when the fiber laser operates in the amplifier similariton state, the filter plays a key role in pulse and spectral reshaping, whereas the nonlinear polarization rotation become less dominant. The dependence of the operational states on the filter bandwidth, fiber length, small signal gain coefficient and orientation of waveplates has also been calculated. A Yb-doped doubled-cladding fiber laser, mode-locked by nonlinear polarization rotation, has also been demonstrated and all of the four pulse regimes are obtained experimentally.
Highlights
The mode-locked fiber laser shows the key features of a broadband spectrum, high peak power, ultrashort pulse width, high beam quality and high quantum efficiency [1]–[4]
Our previous studies [16] illustrate that when the nonlinear polarization rotation (NPR) has a strong effect on the pulse reshaping, the central region of the pulse passed through the polarization beam splitter (PBS) losslessly: the rejected pulse consists of only the leading and trailing edges of the intra-cavity pulse
A birefringent quartz plate with a thickness of 4.09 nm was inserted in the cavity, serving as a filter combining with the PBS and the ISO
Summary
The mode-locked fiber laser shows the key features of a broadband spectrum, high peak power, ultrashort pulse width, high beam quality and high quantum efficiency [1]–[4]. The evolutions of the pulse and the spectrum in the cavity are described, while the effect of GVD and the nonlinearity on the pulse reshaping, under different mode-locking regimes, are analyzed.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.