Coherence-controlled chaotic soliton bunch.

Controlling the coherence of chaotic soliton bunch holds the promise to explore novel light-matter interactions and manipulate dynamic events such as rogue waves. However, the coherence control of chaotic soliton bunch remains challenging, as there is a lack of dynamic equilibrium mechanism for stochastic soliton interactions. Here, we develop a strategy to effectively control the coherence of chaotic soliton bunch in a laser. We show that by introducing a lumped fourth-order-dispersion (FOD), the soliton oscillating tails can be formed and generate the potential barriers among the chaotic solitons. The repulsive force between neighboring solitons enabled by the potential barriers gives rise to an alleviation of the soliton fusion/annihilation from stochastic interactions, endowing the capability to control the coherence in chaotic soliton bunch. We envision that this result provides a promising test-bed for a variety of dynamical complexity science and brings new insights into the nonlinear behavior of chaotic laser sources.

Impact of third-order dispersion on the dynamics of dissipative solitons in an ultrafast fiber laser.

Dissipative solitons (DSs), due to the complex interplay among dispersion, nonlinear, gain and loss, illustrate abundant nonlinear dynamics behaviors. Especially, dispersion plays an important role in the research of DS dynamics in ultrafast fiber lasers. Previous studies have mainly focused on the effect of even-order dispersion, i.e., group velocity dispersion (GVD) and fourth-order dispersion. In fact, odd-order dispersions, such as third-order dispersion (TOD), also significantly influences the dynamics of DSs. However, due to the lack of dispersion engineering tools, few experimental researches in this domain have been reported. In this work, by employing a pulse shaper in ultrafast fiber laser, an in-depth exploration of the DS dynamics influenced by TOD was conducted. With the increase of TOD value, the stable single DS undergoes a splitting into two solitons and then enters explosion state, and ultimately evolves into a chaotic state. The laser operation state is correlated to dispersion profile, which could be controlled by TOD. Here, the positive dispersion at long-wavelength side will be gradually shifted to negative dispersion by increasing the TOD, where soliton effect will drive the transitions. These findings offer valuable insights into the nonlinear dynamics of ultrafast lasers and may also foster applications involving higher-order dispersion.

Auto-setting multi-soliton temporal spacing in a fiber laser by a hybrid GA-PSO algorithm.

Multi-soliton operation in fiber lasers is a promising platform for the investigation of soliton interaction dynamics and high repetition-rate pulse. However, owing to the complex interaction process, precisely manipulating the temporal spacing of multiple solitons in a fiber laser is still challenging. Herein, we propose an automatic way to control the temporal spacing of multi-soliton operation in an ultrafast fiber laser by a hybrid genetic algorithm-particle swarm optimization (GA-PSO) algorithm. Relying on the intelligent adjustment of the electronic polarization controller (EPC), the on-demand temporal spacing of the double solitons can be effectively achieved. In particular, the harmonic mode locking with equal temporal spacing of double solitons is also obtained. Our approach provides a promising way to explore nonlinear soliton dynamics in optical systems and optimize the performance of ultrafast fiber lasers.

Anti-phase pulsation of counter-propagating dissipative solitons in a bidirectional fiber laser.

Due to its unique geometric structure, the bidirectional ultrafast fiber laser is an excellent light source for dual-comb applications. However, sharing the same gain between the counter-propagating solitons also gives rise to complex dynamics. Herein, we report the anti-phase pulsation of counter-propagating dissipative solitons in a bidirectional fiber laser. The in-phase and anti-phase soliton pulsation can be manipulated by adjusting the intracavity birefringence. The periodic modulation of polarization-dependent gain (PDG) caused by polarization hole burning (PHB) in the gain fiber can be responsible for anti-phase pulsation of bidirectional dissipative solitons. These findings offer new, to the best of our knowledge, insights into the complex dynamics of solitons in dissipative optical systems and performance improvement of bidirectional ultrafast fiber lasers.

Dissipative rogue waves generated by multi-soliton explosions in an ultrafast fiber laser.

Derived from oceanography, nowadays the investigation of rogue waves (RWs) has been widely spread in various fields, particularly in nonlinear optics. Passively mode-locked fiber laser has been regarded as one of the excellent platforms to investigate the dissipative RWs (DRWs). Here, we report the observation of DRW generation induced by single and multi-soliton explosions in a passively mode-locked fiber laser. It was demonstrated that through the gain-mediated soliton interactions, one soliton could erupt because of the explosion of another soliton in the laser cavity. Meanwhile, the high-amplitude waves, which fulfill the DRWs criteria, could be detected in the multi-soliton explosion states. The DRWs were identified by characterizing the peak intensity statistics of the time-stretched soliton profiles. Particularly, it was found that the ratio between the highest recorded amplitudes and significant wave heights (SWHs) of DRWs induced by multi-soliton explosions is higher than that by single-soliton explosion case. Our findings will further contribute to the understanding of the physical mechanisms of DRWs in the soliton explosion regime.

A Porous Hexagonal Prism Shaped C-In2-xCoxO3 Electrocatalyst to Expedite Bidirectional Polysulfide Redox in Li-S Batteries.

The shuttling behavior of soluble lithium polysulfides (LPSs) extremely restricts the practical application of lithium sulfur batteries (Li-S batteries). Herein, the hollow porous hexagonal prism shaped C-In2-xCoxO3 composite is synthesized to restrain the shuttle effect and accelerate reaction kinetics of LPSs. The novel hexagonal prism porous carbon skeleton not only provides a stable physical framework for sulfur active materials but also facilitates efficient electron transferring and lithium ion diffusion. Meanwhile, the polar In2-xCoxO3 is equipped with strong adsorption capacity for LPSs, which is confirmed by density functional theory (DFT) calculations, helping to anchor LPSs. More importantly, the doping of Co regulates the electronic structure environment of In2O3, expedites the electron transmission, and bidirectionally improves the catalytic conversion ability of LPSs and nucleation-decomposition of Li2S. Benefiting from the above advantages, the electrochemical performance of Li-S batteries has been greatly enhanced. Therefore, the C-In2-xCoxO3 cathode presents a good rate performance, which exhibits a low-capacity fading rate of 0.052% per cycle over 800 cycles at 5 C. Especially, even under a high sulfur loading of 4.8 mg cm-2, the initial specific capacity is as high as 903 mAh g-1, together with a superior capacity retention of 85.6% after 600 cycles at 0.5 C.

Pulsating dynamics in a pure-quartic soliton fiber laser.

We numerically investigate the pulsating dynamics of pure-quartic solitons (PQSs) in a passively mode-locked fiber laser. The bifurcation diagrams show that the PQS can alternate between the stable single soliton and pulsating regimes multiple times before transiting into the chaotic state. This multi-alternation behavior can be attributed to energy redistribution across the central part and the oscillating tails of the PQS, which is caused by an imperfect counterbalance between self-phase modulation (SPM)-induced and fourth-order dispersion (FOD)-induced phase shifts. Soliton creeping behavior can be observed during the pulsating process, accompanied by periodic asymmetric temporal profiles and central wavelength shifts of the PQS. These findings give new insights into the dynamics of PQSs in fiber lasers.

Harvesting Solar Energy by Flowerlike Carbon Cloth Nanocomposites for Simultaneous Generation of Clean Water and Electricity.

Harvesting solar energy for photothermal conversion in an efficient manner for steam-electricity cogeneration is particularly opportune in the context of comprehensive solar utilization to address the challenge of a global shortage of fresh water. However, the fragile solar thermal devices and the single-energy utilization pattern greatly hinder extensive solar energy exploitation and practical application. Herein, a flexible carbon cloth nanocomposite with a biomimetic pelargonium hortorum-petal-like surface that embraces all desirable chemical and physical properties, that is, enhanced light acquisition, excellent photothermal property, and operational durability, for high-performance solar-driven interfacial water evaporation distillation is reported. Combined with the two-dimensional water channel, the solar evaporator shows a solar-to-steam conversion efficiency of 93% under the simulated solar illumination of 1 kW m-2. More strikingly, the solar steam generation-induced electricity based on the practical consideration toward more infusive solar thermal application is proposed. Such integrative steam-electricity generators presented here provide an attractive method to produce on-site electricity and fresh water in an individualized mode in various resource-constrained areas.

Reasonably Introduced ZnIn2S4@C to Mediate Polysulfide Redox for Long-Life Lithium-Sulfur Batteries.

In consideration of the inferior rate performance and low sulfur utilization of lithium-sulfur batteries (LSBs), an effective strategy via combining polar materials with the conductive carbon sulfur host is widely applied. Herein, metal organic framework-derived in situ-developed ZnIn2S4@C is innovatively synthesized to mediate lithium polysulfide (LPS) conversion based on high electron conductivity and strong chemical interactions for advanced LSBs. Polar ZnIn2S4 possesses strong chemisorption in keeping with the DFT calculation results and catalytic for LPSs, ensuring a high sulfur utilization. Meanwhile, the hollow non-polar carbon frame possessing hierarchical pores not only provides internal space to contain active species but also accommodates efficient electronic transferring and diffusion of lithium ions in the process of cycling. The above advantages make the electrode possess promising stability and good rate performances, achieving long-term and high-rate cycling. Thus, under a sulfur loading of 1.5 mg cm-2, after 500 cycles, at 2 and 5 C, the as-prepared ZnIn2S4@C@S delivers reversible capacities of 734 mA h g-1 (75.7% of the initial capacity with a dropping rate of 0.015% per cycle) and 504 mA h g-1 (68.5% of the primal capacity with a dropping rate of 0.029% per cycle), respectively. Even at a high sulfur loading of 5.0 mg cm-2, at 5 C, 65.6% of the initial capacity can be maintained with a low fading rate of 0.430% per cycle after 500 loops with a high Coulombic efficiency of around 99.8%.

Heterojunction-structured MnCO3@NiO composites and their enhanced electrochemical performance.

The conductivity and stability of materials have always been the main problems hindering the development of lithium-ion battery applications. Here, we successfully construct MnCO3@NiO composites with unique heterogeneous structure via the epitaxial growth of porous NiO nanosheets (thickness: ∼125 nm) on MnCO3 microspheres (diameter: ∼3 µm) to be the anode of lithium-ion batteries. The synergistic effect provided by this special heterogeneous structure effectively improves the electrochemical kinetics, specific surface area as well as structural stability of the composites, finally resulting in predictable enhanced comprehensive electrochemical performance. The electrochemical results show that the MnCO3@NiO composites exhibit a reversible discharge capacity of 624 mA h g-1 at a current density of 1.0 A g-1 up to 300 cycles.

Facile synthesis of Co3-xMnxO4/C nanocages as an efficient sulfur host for lithium-sulfur batteries with enhanced rate performance.

Capacity reduction mainly caused by the shuttle effect and low conductivity restricts the commercial application of lithium-sulfur batteries (LSBs). Herein, we developed a method to overcome these two obstacles synchronously by designing nitrogenous carbon decorated hollow Co3-xMnxO4/C nanocages as hosts of sulfur. These hosts were derived from manganese doped ZIF-67 by a facile sintering method, which provided polar surface to anchor lithium polysulfides and considerable electronic conductivity. The polar material Co3-xMnxO4 and special hollow frame contribute to efficient synergistic sulfur-fixation, resulting in great cycling stabilities. The manganese elements ensure an efficient conversion among LSPs. At the same time, N-doped carbon provides excellent electrical conductivity, thereby leading to splendid rate performances. Thus, a battery with great stability and high capacity could be achieved. As a result, Co3-xMnxO4/C/S with 66 wt% sulfur content delivered a high initial capacity of 1082 mA h g-1 at 1C, together with a slow average capacity decay of 0.056% per cycle at 10C over 500 cycles. When the average sulfur loading is 1.3 mg cm-2, a capacity of 628 mA h g-1 can be maintained at 5C after 500 cycles.