研究目的
Investigating the non-stationary pulse dynamics consisting of explosion events and chaotic multi-pulsing in a passively mode-locked all-normal dispersion fiber laser operating in noise-like pulse state.
研究成果
The paper presents experimental evidence of Raman rogue waves having amplitude exceeding the pump amplitude in real-time laser spectrum observed during explosion in NLP state of operation in an all-normal dispersion fiber laser. The laser also operates in chaotic multi-pulse state with relative inter-pulse drift with unique oscillating trajectory arising from gain dynamics. The results add to the existing knowledge of intermittent and non-stationary pulse dynamics in mode-locked fiber lasers.
研究不足
The study is limited to the observation of non-stationary pulse dynamics in a specific configuration of an all-normal dispersion Yb-fiber laser. The findings may not be directly applicable to other types of fiber lasers or operating conditions.
1：Experimental Design and Method Selection:
The study utilized a nonlinear amplifying loop mirror (NALM) as a mode-locker with a sinusoidally modulating transfer function and a unidirectional ring cavity formed using a circulator and a polarization controller. The NALM was formed using a 50/50 coupler and consisted of a 2 m long in-house fabricated Yb-doped double-clad fiber pumped through a multimode pump combiner, a cladding mode stripper, another PC and 17 m long single mode fiber. The real-time spectrum was acquired through dispersive Fourier transform (DFT) measurement over 1200 roundtrips.
2：Sample Selection and Data Sources:
The output was characterized using a 5 GHz photodiode, a 2.5 GHz oscilloscope, and an optical spectrum analyzer. The DFT measurement was performed using 10 km long G652.d fiber having normal dispersion at 1 μm.
3：5 GHz oscilloscope, and an optical spectrum analyzer. The DFT measurement was performed using 10 km long Gd fiber having normal dispersion at 1 μm.
List of Experimental Equipment and Materials:
3. List of Experimental Equipment and Materials: The setup included a NALM mode-locker, a circulator, polarization controllers, a 50/50 coupler, Yb-doped double-clad fiber, single mode fiber, a photodiode, an oscilloscope, and an optical spectrum analyzer.
4：Experimental Procedures and Operational Workflow:
The PCs were arbitrarily rotated until a stable mode-locked pulse train was observed. The real-time spectrum was recorded over 1200 roundtrips for different PC orientations and pump powers.
5：Data Analysis Methods:
The evolution of real-time NLP spectrum and temporal pulse evolution over consecutive roundtrips were analyzed to observe explosion events and chaotic multi-pulse dynamics.
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