We proposed the simultaneous wavelength extensions of single-cavity dual-wavelength pulses by using a single erbium-doped fiber amplifier and one section of high nonlinear fiber. By additionally introducing a polarization dependent isolator, polarization dependent loss based gain profile tuning is adopted to obtain dual-wavelength pulses centered at 1533.7 and 1554.8nm. When both dual-wavelength pulses are simultaneously launched into the same erbium-doped fiber amplifier with the bidirectional pump power, the spectral range of the output pulses could be expanded to be from 1500 to 1600nm. Subsequently, the amplified dual-wavelength pulses further pass through a section of high nonlinear fiber, extending the spectrum from 1.2μm to more than 1.75μm. Dual-wavelength pulses are amplified simultaneously by using only one amplifier, showing the feasibility of the simplification of single-cavity dual-comb pulse amplification. These results show the high potential in the applications such as multi-color laser generation and spectroscopy.
Synchronous nanosecond and femtosecond pulses delivered from a low-repetition-rate Er-doped fiber laser mode-locked by nonlinear polarization evolution is experimentally proposed. Here, the repetition rate is set as ~4.5 MHz by introducing sufficiently long fiber in a ring cavity. By fully exploiting long fiber and anti-saturation absorption characteristics, it is experimentally observed that dissipative-soliton-resonance pulse with the nanosecond-level pulsewidth and femtosecond soliton pulse synchronously propagate in the same cavity. Besides, the pulsewidth of dissipative-soliton-resonance pulse and laser output power could be tailored by finely configuring the bidirectional pump powers. These results provide deep understanding of low-repetition-rate pulse laser and an intriguing way to obtain tunable dual-scale synchronous pulses, indicating the high potential for multiple-pulse laser processing and so on.
We proposed the emission of wavelength-switchable dual-wavelength-comb pulses in a practical-filter-free cavity. Based on the polarization dependent loss based gain profile tuning, lasings in triple independent gain subregions, i.e. ~1530-, ~1543- and ~1555-nm gain subregions, of erbium-doped fiber, are experimentally observed. Mode-locked by hybrid mechanisms combining carbon nanotube and nonlinear polarization evolution, triple types of dual-wavelength pulses distributed in different dual gain subregions are experimentally obtained. They are distributed in above triple gain subregions and could be switched by adjusting the intracavity polarization controller. These results provide a simple yet effective route to obtain dual-wavelength-comb pulses without additional practical filter and show the high potential in the applications of single-cavity dual-comb metrology.
We investigated a stable single-cavity dual-wavelength-comb fiber laser with significant difference of pulse characteristics. Switchable single/dual-wavelength pulses across 1530- and 1550-nm gain regions are obtained by adjusting the intracavity linear loss. In the dual-wavelength operation, the repetition rates fluctuate and drift in more than 145 Hz, while the standard deviation of the repetition rate difference is measured as 64 mHz in 1000-second monitoring. The passive mutual coherence between pulses is comparable or somewhat better than the reported one under the similar disturbance and monitoring condition. Meanwhile, the significant difference of dual-wavelength pulse characteristics, including spectral bandwidth, pulse energy and dispersion is observed and discussed. The qualified stability is also attributed to the significant pulse difference, which could suppress the nonlinear pulse interaction induced instability. These results provide further physical understanding of the construction of dual-wavelength-comb pulse fiber laser, showing the high potential to promote the performance improvement of dual-comb metrology such as dual-comb spectroscopy, and ranging.
We proposed the triple-wavelength pulses across the 1530- and 1550-nm gain regions are emitted from a carbon nanotube mode-locked ring fiber laser by simultaneously exploiting intracavity loss-based gain profile tuning, Lyot filter effect, and nonlinear polarization evolution. A polarization beam splitter with 2×1-m intracavity polarization-maintaining fiber pigtails is additionally introduced in a typical ring fiber cavity. Polarization-dependent loss is firstly adjusted to equalize the 1530- and 1550-nm gain regions. Except for the triple-wavelength pulses based on Lyot filter and loss-based gain profile tuning, another type of triple-wavelength pulses, i.e. single-wavelength pulse centered at 1530-nm gain region and spectral-overlapping dual-wavelength pulses centered at 1550-nm gain region, are observed by additionally introducing nonlinear polarization evolution. These intriguing results show the feasibility of multi-wavelength pulse generation based on multiple soliton formation mechanisms and the high potential to construct a single-cavity multiple-comb source with versatile pulse characteristics.
We experimentally investigated the build-up dynamics of single-cavity dual-wavelength-comb pulses emitted from a ring fiber cavity with Lyot filter configuration. Dual-wavelength lasers are firstly observed by adjusting the polarization controller to control Lyot filter effect. When the pump powers of the bidirectional pumps are set as 57 mW and 49 mW respectively, dual-wavelength pulses with the center wavelengths of 1546.2 nm and 1563.6 nm and spectral bandwidths of 2 nm and 1.6 nm are obtained. Subsequently, time-stretched dispersive Fourier transform spectroscopy is adopted to monitor the build-up process of dual-wavelength pulses. When switching on the pump diode, the three-stage build-up process from background noise to stable dual-wavelength pulses is experimentally observed. The build-up time is at the level of hundreds of milliseconds. These results provide a deep understanding of single-cavity dual-wavelength-comb pulse generation and contribute to the design and control of the single-cavity dual-comb pulses.
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