A theoretical and experimental study on all-normal-dispersion Yb-doped mode-locked fiber lasers

We report on a theoretical and experimental study of an all-normal-dispersion （ANDi） Yb-doped mode-locked fiber laser, in which nonlinear polarization rotation （NPR） is used to realize mode-locking without any dispersion compensation. Based on the coupled nonlinear Schr6dinger （CNLS） equation, a model simulating the mode-locked process of an all-normal-dispersion ring fiber laser is developed, which shows that the achievement of stable mode-locking depends on the alignment of the polarization controller （PC） along the fast-polarization axis of the fiber, the birefringence intensity, and the net cavity dispersion. According to the theoretical analysis, stable mode-locked pulses with pulse duration 300 ps and average output power 33.9 mW at repetition rate 36 MHz are obtained.

Experimental Investigation of Wavelength-Tunable All-Normal-Dispersion Yb-Doped Mode-Locked Fiber Lasers:Compression and Amplification

Wavelength-tunable ultrashort pulse source with high energy is highly desired for a lot of applications. The wavelength-tunable all-normal-dispersion （ANDi） mode-locked fiber laser, which can be compressed easily and amplified by an all-fiber structure, is a promising seed of such a source with compact structures. The pulse compression and amplification at different center wavelengths （from 1026 to 1058nm） of the tunable ANDi Yb- doped mode-locked fiber lasers that we previously proposed are experimentally investigated in this work. It is found that, for different wavelengths, the duration and chirp of the direct output pulse from the oscillator vary considerably, however, the duration of compressed pulse fluctuates less. For the amplification process, due to the unf/at gain spectrum of Yb-doped fiber, the gain at a short wavelength is larger than that at a long wavelength. Consequently, the trends of spectrum distortions induced by the amplification process are different for different wavelengths. These results and analyses will be helpful for the design of a high-energy and wavelength-tunable ultrashort pulse source based on an ANDi seed.

Tunable,High-Order Harmonically Mode-Locked All-Normal-Dispersion Ytterbium Fiber Laser

We report the generation of passively tunable high peak signal-to-noise ratio harmonic mode-locked （HML） all- normal-dispersion Yb-doped fiber laser with a single birefringent filter in a ring cavity configuration. The highest fourth harmonic of the fundamental mode-locked frequency at a repetition rate of 88 MHz is obtained. The pulses are compressed to 627fs by using an external grating-pair compressor. For the fourth HML output, the peak signal-to-noise ratio of the rf is 73dB and the average power is as high as 110mW with the pump power of 500mW. Soliton bunches which contain multipulses are also observed in the weak mode-locked regime of the HML, and the separation between interpulses in a dissipative soliton bunch can be controlled by adjustment of the waveplates and spectral filter in the cavity：

Wavelength-tunable dissipative soliton from Yb-doped fiber laser with nonlinear amplifying loop mirror

We report a Yb-doped mode-locked fiber laser based on a nonlinear amplifying loop mirror[NALM],which is all-normaldispersion[ANDi],and allows the output wavelength to be tunable.The laser can generate a stable femtosecond dissipative soliton with a maximum output power of 196 mW.Its repetition rate is 112.4 MHz,and the final pulse duration is 236 fs.By adjusting the angle of the reflective diffraction grating,the mode-locked fiber laser was realized to tune the output with a tuning range of 54 nm from 1011.8 nm to 1065.6 nm.To the best of our knowledge,this is the widest tuning range of an ANDi Yb-doped mode-locked fiber laser based on NALM.