分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： We have demonstrated a mode-locked Mamyshev oscillator based on a single-mode-fibre configuration with low threshould. The influences of spectral filters and the pump power on the output laser characteristics have been investigated. In the case with spectral-filter central wavelength far away from the peak of gain spectrum, the laser pulses have deviated slightly from similariton evolution with gain-shaping under high pump power. Moreover, self-starting mode-locking operation has been realized when the pump power was only 520 mW, which might benefit from the appropriate polarization conditions and small spectral filter separation. The laser can generate 1.89-nJ ultra-short pulses with 20-dB spectral width of 54.6 nm. The pulse duration can be compressed externally to 64.69 fs with the peak power of 21.3 kW.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： We demonstrate a novel approach to achieve wavelength-tunable ultrashort pulses from an all-fiber mode-locked laser with a saturable absorber based on nonlinear Kerr beam clean-up effect. This saturable absorber was formed by a single-mode fiber spliced to a graded-index multimode fiber, and its tunable band-pass filter effect is studied by a numerical model. By adjusting the bending condition of graded-index multimode fiber, the laser could produce dissipative soliton pulses with their central wavelength tunable from1040 nm to 1063 nm. The pulse width of output laser could be compressed externally to 791 fs, and the signal to noise ratio of its radio frequency spectrum was measured to be 75.5 dB. This work provides a new idea for the design of wavelength-tunable mode-locked laser which can be used as an attractive light source in communication system.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： Multimode fiber systems are desirable for industrial and scientific applications. As an interesting effect for the laser beam propagation in a multimode fiber, nonlinear Kerr beam cleanup has attracted considerable research interest due to the spatial beam compressing. However, its physical mechanisms, especially the influences of input conditions on its performances, remain unclear. Here, we report a new self-organized regime for the multimode beam propagation in a graded-index multimode fiber: when the input laser has a dominant mode in which most of the laser energy is concentrated, the beam profile can be maintaining in a well-defined structure similar to the input dominant mode in nonlinear regime, while it will evolve to an irregular pattern in linear regime. The existence and universality of this nonlinear beam self-maintaining effect have been verified by the experimental and numerical data. Our results also provide evidence that nonlinear Kerr effects can be the driving mechanism and nonlinear Kerr beam cleanup is a specific case of this effect. Further research into this spatial beam shaping effect may provide a new perspective to understand other multimode fiber nonlinearities.
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