Abstract
We report experimental observations and numerical simulation results on the spectrum moving, narrowing, broadening, and wavelength switching of dissipative solitons (DSs) in an all-normal-dispersion Yb-fiber laser that is passively mode-locked by using the nonlinear polarization rotation (NPR) technique. We found numerically that the DS spectrum moving, together with spectrum narrowing/broadening, is caused by the effective gain profile change resulted from the moving of the artificial spectral filter. Furthermore, we show that the wavelength switching observed in the laser is a natural consequence of the effective gain switching. The moving of the artificial spectral filter could be originated from either the cavity birefringence change or the polarizer rotation. Due to the broad gain and the artificial birefringent filter introduced by the NPR technique, apart from the central wavelength shifting and bandwidth changing, wavelength switching of DSs could be obtained by simply rotating the polarizer. Numerical simulations well reproduced the experimental observations. Our results suggest that extra effort should be made for wavelength tuning if there is any polarization-dependent component in the cavity as the wavelength switching will interrupt the continuously wavelength shift.
Highlights
Dissipative solitons (DSs) exist in a wide range of physical systems [1]
DSs have been observed in mode locked fiber lasers, and their dynamics is described by the complex Ginzburg– Landau equation (GLE)
Extensive researches have shown that spectral filtering played a crucial role on the DS formation in fiber lasers, where spectral filtering can be provided by the gain bandwidth, for example in the case of Erbium-doped fiber (EDF) lasers [4]; or generated by a bandpass filter with narrow bandwidth as in the cases of Yb-doped fiber (YDF) lasers [6]; or by an equivalent artificial filter with narrow passband [9]–[12]
Summary
Dissipative solitons (DSs) exist in a wide range of physical systems [1]. In optics, DSs have been observed in mode locked fiber lasers, and their dynamics is described by the complex Ginzburg– Landau equation (GLE). Continuous soliton wavelength tuning in a range of 29 nm was demonstrated in an anomalous fiber laser by rotating the orientation of an intracavity birefringent filter [13]. Generation of tunable single- and dual-wavelength dissipative solitons in an all-normal-dispersion mode-locked Yb-doped fiber laser was reported recently. As the DSs are the consequence of the combined effects among the cavity dispersion, fiber nonlinearity, gain and loss, and spectral filtering, it is desired to study the DS wavelength tuning/switching behaviors beyond the experimental observations, especially when the intra-cavity spectral filter has multiple passbands. Numerical simulations well reproduced the experimental observations and suggested that the spectrum tuning and the wavelength switching are caused by the change of the effective gain, which is determined by either the cavity birefringence or the orientation of the intracavity polarization. Our results show that extra effort should be made for wavelength tuning if there is any polarization dependent component in the cavity as the wavelength switching will interrupt the continuously wavelength tuning
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