Browsing by Author "Zeng, Chao"

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Birefringence-Induced Heterogeneous Vector Pulses in Ultrafast Fiber Lasers
(2022-10) Mao, Dong; Gao, Qun; Li, Jingyi; He, Zhiwen; Du, Yueqing; Zeng, Chao; Sun, Zhipei; Zhao, Jianlin
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Single-mode fiber lasers are capable of supporting trapped vector solitons with two similar orthogonally polarized components, due to the delicate balance between fiber birefringence and chromatic dispersion. Here, we demonstrate that heterogeneous vector pulses (HVPs) universally exist in anomalous-dispersion and near-zero-dispersion regimes, from hybrid-structure fiber lasers composed of low- and high-birefringent fibers. The vector pulses include two distinct orthogonally polarized components, one of which is a robust pulse, while the other is a gradually attenuated wavepacket composed of terahertz- (THz) repetition-rate subpulses. Simulation and analytical results fully reproduce experimental observations and demonstrate that the robust pulse couples a fraction of its energy to the orthogonally polarized component per roundtrip at the high-birefringent fiber, forming the unique HVPs. Apart from the intriguing nonlinear dynamics, the HVP can work as a flexible workhorse for various applications, ranging from optical polarization multiplexing to THz synthesis and optical precision spectroscopy.
The dissipative Talbot soliton fiber laser
(2024-03-15) Zhang, Heze; Du, Yueqing; Zeng, Chao; Sun, Zhipei; Zhang, Yong; Zhao, Jianlin; Mao, Dong
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Talbot effect, characterized by the replication of a periodic optical field in a specific plane, is governed by diffraction and dispersion in the spatial and temporal domains, respectively. In mode-locked lasers, Talbot effect is rarely linked with soliton dynamics since the longitudinal mode spacing and cavity dispersion are far away from the self-imaging condition. We report switchable breathing and stable dissipative Talbot solitons in a multicolor mode-locked fiber laser by manipulating the frequency difference of neighboring spectra. The temporal Talbot effect dominates the laser emission state-in the breathing state when the integer self-imaging distance deviates from the cavity length and in the steady state when it equals the cavity length. A refined Talbot theory including dispersion and nonlinearity is proposed to accurately depict this evolution behavior. These findings pave an effective way to control the operation in dissipative optical systems and open branches in the study of nonlinear physics.
Heteronuclear multicolor soliton compounds induced by convex-concave phase in fiber lasers
(2023-12) Zhang, Heze; Mao, Dong; Du, Yueqing; Zeng, Chao; Sun, Zhipei; Zhao, Jianlin
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Optical solitons emerging from fiber resonators generally possess similar properties that hinge on the system parameters. However, the generation of wavepackets composed of dissimilar solitons within the same laser cavity is still challenging in ultrafast lasers. Here, we report on heteronuclear multicolor soliton compounds composed of chirp-free conventional solitons and chirped dissipative solitons, by introducing convex-concave frequency phases in mode-locked fiber lasers. In spite of different lasing wavelengths, the dissipative solitons always overlap with the conventional solitons, giving birth to trains of modulated wavepackets. The resonant sidebands of two types of solitons follow from the same phase-matching principle dominated by the absolute value of cavity dispersion. Simulations fully substantiate the experimental results, confirming that the overlapping of two solitons is dominated by the co-action of saturable absorption and group-delay compensation. It is demonstrated that the phase-managed dissipative system is capable of supporting multicolor soliton compounds with distinct properties, offering an effective platform to reveal the interaction of dissimilar nonlinear wavepackets.
Phase-matching-induced near-chirp-free solitons in normal-dispersion fiber lasers
(2022-01-25) Mao, Dong; He, Zhiwen; Zhang, Yusong; Du, Yueqing; Zeng, Chao; Yun, Ling; Luo, Zhichao; Li, Tijian; Sun, Zhipei; Zhao, Jianlin
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Direct generation of chirp-free solitons without external compression in normal-dispersion fiber lasers is a long-term challenge in ultrafast optics. We demonstrate near-chirp-free solitons with distinct spectral sidebands in normal-dispersion hybrid-structure fiber lasers containing a few meters of polarization-maintaining fiber. The bandwidth and duration of the typical mode-locked pulse are 0.74 nm and 1.95 ps, respectively, giving the time-bandwidth product of 0.41 and confirming the near-chirp-free property. Numerical results and theoretical analyses fully reproduce and interpret the experimental observations, and show that the fiber birefringence, normal-dispersion, and nonlinear effect follow a phase-matching principle, enabling the formation of the near-chirp-free soliton. Specifically, the phase-matching effect confines the spectrum broadened by self-phase modulation and the saturable absorption effect slims the pulse stretched by normal dispersion. Such pulse is termed as birefringence-managed soliton because its two orthogonal-polarized components propagate in an unsymmetrical “X” manner inside the polarization-maintaining fiber, partially compensating the group delay difference induced by the chromatic dispersion and resulting in the self-consistent evolution. The property and formation mechanism of birefringence-managed soliton fundamentally differ from other types of pulses in mode-locked fiber lasers, which will open new research branches in laser physics, soliton mathematics, and their related applications.
Soliton metamorphosis dynamics in ultrafast fiber lasers
(2021-05-17) He, Zhiwen; Du, Yueqing; Zeng, Chao; Jiang, Biqiang; Mao, Dong; Sun, Zhipei; Zhao, Jianlin
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
The transitions from the incoherent noise to the coherent soliton have been fully revealed in ultrafast lasers. However, the soliton transformation between different coherent states, termed as soliton metamorphosis, remains an attractive yet uncharted territory. Here, we reveal the ultrafast dynamics of the soliton metamorphosis via single-shot spectroscopy in a specially designed fiber laser capable of emitting fast-switchable dissipative solitons and stretched pulses. It is demonstrated that the soliton metamorphosis is a consecutive evolution process including the self-phase modulation stage, pulse split stage, and transient stretched pulse stage. Particularly, the long-period pulse breathing and the spectral period doubling appear in the forepart and middle part of the last stage. The metamorphosis dynamics and soliton properties are substantiated by numerical simulation based on a three-step model. This work not only unveils the transient evolution physics of the pulse in soliton metamorphosis, but also provides a simple and effective way to control operations of ultrafast lasers.
Synchronized multi-wavelength soliton fiber laser via intracavity group delay modulation
(2021-11-18) Mao, Dong; Wang, Huaqiang; Zhang, Heze; Zeng, Chao; Du, Yueqing; He, Zhiwen; Sun, Zhipei; Zhao, Jianlin
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Locking of longitudinal modes in laser cavities is the common path to generate ultrashort pulses. In traditional multi-wavelength mode-locked lasers, the group velocities rely on lasing wavelengths due to the chromatic dispersion, yielding multiple trains of independently evolved pulses. Here, we show that mode-locked solitons at different wavelengths can be synchronized inside the cavity by engineering the intracavity group delay with a programmable pulse shaper. Frequency-resolved measurements fully retrieve the fine temporal structure of pulses, validating the direct generation of synchronized ultrafast lasers from two to five wavelengths with sub-pulse repetition-rate up to similar to 1.26 THz. Simulation results well reproduce and interpret the key experimental phenomena, and indicate that the saturable absorption effect automatically synchronize multi-wavelength solitons in despite of the small residual group delay difference. These results demonstrate an effective approach to create synchronized complex-structure solitons, and offer an effective platform to study the evolution dynamics of nonlinear wavepackets.
Versatile multi-wavelength ultrafast fiber laser mode-locked by carbon nanotubes
(2013) Liu, Xueming; Han, Dongdong; Sun, Zhipei; Zeng, Chao; Lu, Hua; Mao, Dong; Cui, Yudong; Wang, Fengqiu
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Multi-wavelength lasers have widespread applications (e.g. fiber telecommunications, pump-probe measurements, terahertz generation). Here, we report a nanotube-mode-locked all-fiber ultrafast oscillator emitting three wavelengths at the central wavelengths of about 1540, 1550, and 1560 nm, which are tunable by stretching fiber Bragg gratings. The output pulse duration is around 6 ps with a spectral width of ~0.5 nm, agreeing well with the numerical simulations. The triple-laser system is controlled precisely and insensitive to environmental perturbations with <0.04% amplitude fluctuation. Our method provides a simple, stable, low-cost, multi-wavelength ultrafast-pulsed source for spectroscopy, biomedical research and telecommunications.