Acta Photonica Sinica, Volume. 54, Issue 3, 0314001(2025)
Two Pulse Evolution Routes in Hybrid Mode-locked Ytterbium-doped Fiber Laser
Passively mode-locked fiber lasers, featuring a compact structure, narrow pulse width, and rich nonlinear phenomena, provide an ideal platform for ultrafast laser research owing to their wide range of biomedicine, generation of terahertz radiation, investigation of attosecond dynamics, and communication. Following years of research, a variety of passively mode-locked techniques have been developed and successfully employed to generate ultrashort pulses, such as nonlinear polarization rotation, nonlinear multimode interference, nonlinear amplifying loop mirrors, Mamyshev oscillator, semiconductor saturable absorber mirror, and two-dimensional material. As a typical nonlinear system, the passive mode-locked fiber laser produces pulses that are subject to many factors, including gain, loss, dispersion, nonlinear effects, and spectral filtering. Examples of such phenomena include dissipative solitons or conventional solitons generated under normal or anomalous group velocity dispersion conditions, respectively, and dissipative soliton resonances arising from inverse saturable absorption effects. Similarly, spectral filters, which enable the manipulation of pulses by limiting spectral broadening and promoting intracavity dissipation, are of crucial importance in the context of mode-locked fiber lasers. The state of solitons can be controlled to evolve towards soliton molecules and pulse splitting by bandpass filters or fiber Bragg gratings. The utilization of Lyot filters or multimode interference filters facilitates the generation of sinusoidal spectral filtering within the cavity, which in turn enables the formation of h-shaped pulses, multi-wavelength pulses, and pulses with high repetition frequency. Nevertheless, the majority of the above reports pertain to a singular evolutionary route of pulse, which significantly restricts its applicability in many application scenarios. To move the pulses towards different evolutionary routes within the same laser configuration, we constructed a hybrid mode-locked ytterbium-doped fiber laser based on NPR and SESAM. The saturable absorption effect provided by SESAM enables pulse generation and the sinusoidal spectral filtering provided by NPR enables pulse shaping. Adjusting the polarization controller changes the strength of the spectral filtering. When the spectral filtering is weak, a dissipative soliton mode-locked pulse with a central wavelength of 1 036.64 nm, a 3-dB bandwidth of 1.96 nm, and a pulse width of 17.97 ps is produced. Further adjustment of the polarization controller results in the generation of asynchronous dual-wavelength pulses with central wavelengths of 1 033.22 nm and 1 037.06 nm, corresponding to a repetition frequency difference of 720 Hz. When spectral filtering is strong, it limits the soliton broadening, and the laser is capable of outputting multi-wavelength synchronized mode-locked pulses, with the number of wavelengths switchable from a single wavelength up to seven wavelengths. The analysis of the two pulse evolution routes serves to enhance our comprehension of hybrid mode-locked fiber lasers and offers a novel avenue for the generation of ultrashort pulses exhibiting multiple wavelengths or high repetition frequency.
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Yi YAN, Chenyue LV, Jiajing LANG, Yongsen ZHAO, Mei QI, Baole LU, Jintao BAI. Two Pulse Evolution Routes in Hybrid Mode-locked Ytterbium-doped Fiber Laser[J]. Acta Photonica Sinica, 2025, 54(3): 0314001
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Received: Sep. 3, 2024
Accepted: Jan. 8, 2025
Published Online: Apr. 22, 2025
The Author Email: Baole LU (lubaole1123@163.com)