Diode-Pumped Soliton and Non-Soliton Mode-Locked Yb:GYSO Lasers

Diode-pumped soliton and non-soliton mode-locked Yb:(Gd1−xYx)2SiO5(x=0.5)lasers are demonstrated.Pulses as short as 1.4 ps are generated for the soliton mode−locked operation,with a pair of SF10 prisms as the negative dispersion elements.The central wavelength is 1056 nm and the repetition rate is 48 MHz.For the non-soliton mode locking,the output power could achieve∼1.2 W,and the pulse width is about 20 ps.The critical pulse energy in the soliton-mode locked operation against the Q-switched mode locking is much lower than the critical pulse energy in the non-soliton mode-locked operation.

Antimonene-based saturable absorber for a soliton mode-locked and Q-switched fiber laser in the 2 μm wavelength region

We demonstrate antimonene as a saturable absorber(SA) to generate an ultrafast mode-locked and Q-switched laser in the 2 μm wavelength region. The two antimonene-based SAs were prepared and inserted separately in a thulium–holmiumdoped fiber laser to produce the pulsed laser. Antimonene was coated onto a tapered fiber to generate soliton mode-locked pulses and used in thin-film form for the generation of Q-switched pulses. The mode-locking was stable within a pump power of 267 m W–511 m W, and the laser operated at a central wavelength of 1897.4 nm. The mode-locked laser had a pulse width of 1.3 ps and a repetition rate of 12.6 MHz, with a signal-to-noise ratio of 64 d B. Q-switched laser operation was stable at a wavelength of 1890.1 nm within a pump power of 312 m W–381 m W. With the increase in pump power from 312 m W to 381 m W, the repetition rate increased to a maximum of 56.63 k Hz and the pulse width decreased to a minimum value of 2.85 μs. Wide-range tunability of the Q-switched laser was also realized within the wavelength range of1882 nm–1936 nm.

Soliton mode-locked fiber laser based on topological insulator Bi2Te3 nanosheets at 2 μm

We reported diverse soliton operations in a thulium/holmium-doped fiber laser by taking advantage of a tapered fiber-based topological insulator（TI） Bi2Te3 saturable absorber（SA）.The SA had a nonsaturable loss of 53.5% and a modulation depth of 9.8%.Stable fundamentally mode-locked solitons at 1909.5 nm with distinct Kelly sidebands on the output spectrum,a pulse repetition rate of 21.5 MHz,and a measured pulse width of 1.26 ps were observed in the work.By increasing the pump power,both bunched solitons with soliton number up to 15 and harmonically mode-locked solitons with harmonic order up to 10 were obtained.To our knowledge,this is the first report of both bunched solitons and harmonically mode-locked solitons in a fiber laser at 2 μm region incorporated with TIs.

Compact 517 MHz soliton mode-locked Er-doped fiber ring laser

We report on a compact passive mode-locked Er:fiber ring laser operated at the fundamental repetition rate of 517 MHz, which we believe is the highest fundamental repetition rate ever reported in a ring cavity fiber laser.The key technique is the employment of two innovative high-power wavelength domain multiplexer collimators with all gain fiber cavity suited for the high power(up to 2 W) pumping. The laser is featured with a direct chirpfree output pulse, which is 97 fs without extracavity compression at an average output power of 90 mW.

Femtoseconds soliton mode-locked erbium-doped fiber laser based on nickel oxide nanoparticle saturable absorber

We demonstrate a femtosecond mode-locked erbium-doped fiber laser（EDFL） using a nickel oxide（Ni O） as a saturable absorber（SA）. Ni O nanoparticles are hosted into polyethylene oxide film and attached to fiber ferrule in the laser cavity. The Ni O-SA shows a 39% modulation depth with a 0.04 MW∕cm^2 saturation intensity. Our ring laser cavity based on erbium-doped active fiber with managed intracavity dispersion has the ability to generate ultrashort pulses with a full width at half-maximum（FWHM） of around 2.85 nm centered at 1561.8 nm.The pulses repeat at a frequency of 0.96 MHz and duration of 950 fs.

Comprehensive analysis of pure-quartic soliton dynamics in a passively mode-locked fiber laser

The understanding of soliton dynamics promotes the development of ultrafast laser technology. High-energy purequartic solitons(PQSs) have gradually become a hotspot in recent years. Herein, we numerically study the influence of the gain bandwidth, saturation power, small-signal gain, and output coupler on PQS dynamics in passively mode-locked fiber lasers. The results show that the above four parameters can affect PQS dynamics. Pulsating PQSs occur as we alter the other three parameters when the gain bandwidth is 50 nm. Meanwhile, PQSs evolve from pulsating to erupting and then to splitting as the other three parameters are altered when the gain bandwidth is 10 nm, which can be attributed to the existence of the spectral filtering effect and intra-cavity fourth-order dispersion. These findings provide new insights into PQS dynamics in passively mode-locked fiber lasers.

Multiple Dissipative Solitons in a Long-Cavity Normal-Dispersion Mode-Locked Yb-Doped Fiber Laser

Transitional operations of multiple dissipative solitons in a long-cavity normal-dispersion Yb-doped fiber laser are experimentally investigated.Multiple dissipative solitons,including a stable soliton pair and a soliton triplet are observed by increasing the pump power or adjusting the polarization controllers.Two main boundaries of the stable asymmetric soliton and oscillating soliton are found between steady mode-locking.Moreover,multiple dissipative solitons with greater quantities of solitons are observed with pump power increasing.The experimental results agree well with a previous numerical study of multiple dissipative solitons.

Characteristics of Soliton Evolution in the Wave-Breaking-Free Regime in a Passively Mode-Locked Yb-Doped Fiber Laser

We focus on several aspects concerning the numerical simulation of a passively mode-locked Yb-doped fiber laser by a non-distributed model.The characteristics of soliton evolution in a wave-breaking-free regime are numerically investigated with the split-step Fourier method.Based on the model,a parabolic-shaped soliton with a nearly linear chirp and bound soliton pairs are obtained by controlling the intra-cavity average dispersion of the fiber laser.A phenomenon is observed that by keeping the system parameters unchanged,linearly chirped parabolic soliton and bound soliton pairs are attainable under different initial conditions in the transient region between these two kinds of solitons.

Bound soliton pulses in a passively mode-locked fibre ring laser

The bound solitons in a passively mode-locked fibre ring laser are observed and their formation mechanism is summarized in this paper. In order to obtain stable bound solitons, a strong CW laser field at the centre of the soliton spectral is necessary to suppress and synchronize the random soliton phase variations.

Experimental Observation of Bright and Dark Solitons Mode-Locked with Zirconia-Based Erbium-Doped Fiber Laser

We demonstrate the generation of dark and bright solitons with our homemade zirconia-based erbium-doped fiber and graphene oxide（GO） saturable absorber in anomalous dispersion region.The GO is fabricated using an abridged Hummer＇s method,which is combined with polyethylene oxide to produce a composite film.The film is sandwiched between two optical ferrules and embedded in the laser cavity to enhance its birefringence and nonlinearity.The self-starting bright soliton is easily generated at pump power of 78 mW with the whole length cavity of 14.7 m.The laser produces the bright pulse train with repetition rate,pulse width,pulse energy and central wavelength being 13.9 MHz,0.6 ps,2.74 p J and 1577.46 nm,respectively.Then,by adding the 10 m of single mode fiber into the laser cavity,dark soliton pulse is produced.For the formation of dark pulse train,the measured repetition rate,pulse width,pulse energy and central wavelength are 8.3 MHz,20 ns and 4.98 p J and1596.82 nm,respectively.Both pulses operate in the anomalous region.

Observation of stable bound soliton with dual-wavelength in a passively mode-locked Er-doped fiber laser

A phase-locked bound state soliton with dual-wavelength is observed experimentally in a passively mode-locked Erdoped fiber（EDF） laser with a fiber loop mirror（FLM）. The pulse duration of the soliton is 15 ps and the peak-to-peak separation is 125 ps. The repetition rate of the pulse sequence is 3.47 MHz. The output power is 11.8 mW at the pump power of 128 mW, corresponding to the pulse energy of 1.52 nJ. The FLM with a polarization controller can produce a comb spectrum, which acts as a filter. By adjusting the polarization controller or varying the pump power, the central wavelength of the comb spectrum can be tuned. When it combines with the reflective spectrum of the fiber Bragg grating, the total spectrum of the cavity can be cleaved into two parts, then the bound state soliton with dual-wavelength at 1549.7 nm and 1550.4 nm is obtained.

Soliton mode-locked fiber laser with high-quality MBE-grown Bi2Se3 film

In this work, a soliton mode-locked erbium-doped fiber laser(EDFL) with a high-quality molecular beam epitaxy(MBE)-grown topological insulator(TI) Bi2Se3 saturable absorber(SA) is reported.To fabricate the SA device, a 16-layer Bi2Se3 film was grown successfully on a 100 μm thick SiO2 substrate and sandwiched directly between two fiber ferrules.The TI-SA had a saturable absorption of 1.12% and a saturable influence of 160 MW/cm^2.After inserting the TI-SA into the unidirectional ring-cavity EDFL, self-starting mode-locked soliton pulse trains were obtained at a fundamental repetition rate of 19.352 MHz.The output central wavelength, pulse energy,pulse duration, and signal to noise ratio of the radio frequency spectrum were 1530 nm,18.5 p J, 1.08 ps, and 60d Bm, respectively.These results demonstrate that the MBE technique could provide a controllable and repeatable method for the fabrication of identical high-quality TI-SAs, which is critically important for ultra-fast pulse generation.

Observation of High-Order Femtosecond Solitons in a Self-Mode-Locked Ti:Sapphire Laser

The N=3 femtosecond solitonlike pulses are observed directly in a self-mode-locked Ti:sapphire laser as well as even higher-order solitonlike pulses for the first time.When the laser is operating in a stable train of mode-locked pulses,the periodic pulse train appears by only varying the intracavity dispersion.The soliton period with N=3 corresponds to a cavity round trip number of 164.

Higher-Order Nonlinear Effects on Optical Soliton Propagation and Their Interactions

When pursuing femtosecond-scale ultrashort pulse optical communication, one cannot overlook higher-order nonlinear effects. Based on the fundamental theoretical model of the variable coefficient coupled high-order nonlinear Schr¨odinger equation, we analytically explore the evolution of optical solitons in the presence of highorder nonlinear effects. Moreover, the interactions between two nearby optical solitons and their transmission in a nonuniform fiber are investigated. The stability of optical soliton transmission and interactions are found to be destroyed to varying degrees due to higher-order nonlinear effects. The outcomes may offer some theoretical references for achieving ultra-high energy optical solitons in the future.

Reinforcement Learning for Efficient Identification of Soliton System Parameters Across Expansive Domains

Optical solitons in mode-locked fiber lasers and optical communication links have various applications. Thestudy of transmission modes of optical solitons necessitates the investigation of the relationship between theequation parameters and soliton evolution employing deep learning techniques. However, the existing identificationmodels exhibit a limited parameter domain search range and are significantly influenced by initialization.Consequently, they often result in divergence toward incorrect parameter values. This study harnessed reinforcementlearning to revamp the iterative process of the parameter identification model. By developing a two-stageoptimization strategy, the model could conduct an accurate parameter search across arbitrary domains. Theinvestigation involved several experiments on various standard and higher-order equations, illustrating that theinnovative model overcame the impact of initialization on the parameter search, and the identified parametersare guided toward their correct values. The enhanced model markedly improves the experimental efficiency andholds significant promise for advancing the research of soliton propagation dynamics and addressing intricatescenarios.

Three-Wave Mixing of Dipole Solitons in One-Dimensional Quasi-Phase-Matched Nonlinear Crystals

A quasi-phase-matched technique is introduced for soliton transmission in a quadratic[χ^((2))]nonlinear crystal to realize the stable transmission of dipole solitons in a one-dimensional space under three-wave mixing.We report four types of solitons as dipole solitons with distances between their bimodal peaks that can be laid out in different stripes.We study three cases of these solitons:spaced three stripes apart,one stripe apart,and confined to the same stripe.For the case of three stripes apart,all four types have stable results,but for the case of one stripe apart,stable solutions can only be found atω_(1)=ω_(2),and for the condition of dipole solitons confined to one stripe,stable solutions exist only for Type1 and Type3 atω_(1)=ω_(2).The stability of the soliton solution is solved and verified using the imaginary time propagation method and real-time transfer propagation,and soliton solutions are shown to exist in the multistability case.In addition,the relations of the transportation characteristics of the dipole soliton and the modulation parameters are numerically investigated.Finally,possible approaches for the experimental realization of the solitons are outlined.

Nonlinear-Optical Analogies in Nuclear-Like Soliton Reactions:Selection Rules,Nonlinear Tunneling and Sub-Barrier Fusion–Fission

The main goal of our study is to reveal unexpected but intriguing analogies arising between optical solitons and nuclear physics,which still remain hidden from us.We consider the main cornerstones of the concept of nonlinear optics of nuclear reactions and the well-dressed repulsive-core solitons.On the base of this model,we reveal the most intriguing properties of the nonlinear tunneling of nucleus-like solitons and the soliton selfinduced sub-barrier transparency effect.We describe novel interesting and stimulating analogies between the interaction of nucleus-like solitons on the repulsive barrier and nuclear sub-barrier reactions.The main finding of this study concerns the conservation of total number of nucleons(or the baryon number)in nuclear-like soliton reactions.We show that inelastic interactions among well-dressed repulsive-core solitons arise only when a“cloud”of“dressing”spectral side-bands appears in the frequency spectra of the solitons.This property of nucleus-like solitons is directly related to the nuclear density distribution described by the dimensionless small shape-squareness parameter.Thus the Fourier spectra of nucleus-like solitons are similar to the nuclear form factors.We show that the nuclear-like reactions between well-dressed solitons are realized by“exchange”between“particle-like”side bands in their spectra.

Multiple Soliton Asymptotics in a Spin-1 Bose–Einstein Condensate

Spinor Bose–Einstein condensates(BECs)are formed when atoms in the multi-component BECs possess single hyperfine spin states but retain internal spin degrees of freedom.This study concentrates on a(1+1)-dimensional three-couple Gross–Pitaevskii system to depict the macroscopic spinor BEC waves within the meanfield approximation.Regarding the distribution of the atoms corresponding to the three vertical spin projections,a known binary Darboux transformation is utilized to derive the𝑁matter-wave soliton solutions and triple-pole matter-wave soliton solutions on the zero background,where𝑁is a positive integer.For those multiple matterwave solitons,the asymptotic analysis is performed to obtain the algebraic expressions of the soliton components in the𝑁matter-wave solitons and triple-pole matter-wave solitons.The asymptotic results indicate that the matter-wave solitons in the spinor BECs possess the property of maintaining their energy content and coherence during the propagation and interactions.Particularly,in the𝑁matter-wave solitons,each soliton component contributes to the phase shifts of the other soliton components;and in the triple-pole matter-wave solitons,stable attractive forces exist between the different matter-wave soliton components.Those multiple matter-wave solitons are graphically illustrated through three-dimensional plots,density plot and contour plot,which are consistent with the asymptotic analysis results.The present analysis may provide the explanations for the complex natural mechanisms of the matter waves in the spinor BECs,and may have potential applications in designs of atom lasers,atom interferometry and coherent atom transport.

Navigation Finsler metrics on a gradient Ricci soliton

In this paper,we study a class of Finsler metrics defined by a vector field on a gradient Ricci soliton.We obtain a necessary and sufficient condition for these Finsler metrics on a compact gradient Ricci soliton to be of isotropic S-curvature by establishing a new integral inequality.Then we determine the Ricci curvature of navigation Finsler metrics of isotropic S-curvature on a gradient Ricci soliton generalizing result only known in the case when such soliton is of Einstein type.As its application,we obtain the Ricci curvature of all navigation Finsler metrics of isotropic S-curvature on Gaussian shrinking soliton.

Nondegenerate Soliton Solutions of(2+1)-Dimensional Multi-Component Maccari System

For a multi-component Maccari system with two spatial dimensions,nondegenerate one-soliton and two-soliton solutions are obtained with the bilinear method.It can be seen by drawing the spatial graphs of nondegenerate solitons that the real component of the system shows a cross-shaped structure,while the two solitons of the complex component show a multi-solitoff structure.At the same time,the asymptotic analysis of the interaction behavior of the two solitons is conducted,and it is found that under partially nondegenerate conditions,the real and complex components of the system experience elastic collision and inelastic collision,respectively.