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.

Different operation states of soliton pulses in an erbium-doped fibre ring laser

We report on the experimental observation of soliton pulses in an erbium doped fibre ring laser. The passive mode-locking is achieved using the nonlinear polarization rotation technique. By adjusting the pump power and the intracavity polarization controllers, a normal soliton, a stable 8th harmonic mode-locked pulse and a noise-like pulse have been observed in our laser. The experimental results revealed that the noise-like pulse is not suitable for the optical telecommunication, and in order to obtain the stable harmonic mode-locked soliton, a strong unstable CW laser field is necessary to mediate global soliton interaction. The formation mechanism of the harmonic mode-locked pulse has also been analysed.

Generation of single and multiple dissipative soliton in an erbium-doped fiber laser

We experimentally report on the generation of single and multiple dissipative soliton via nonlinear polarization rotation technique. The spectrum of the mode-locked dissipative soliton exhibits typical steep edges with a flat top; the pulse duration is 10.07 ps. It is found that with the pump power increasing from 110 mW to 161 mW, the top of the mode-locked spectrum becomes flater and the 3-dB spectral bandwidth is broadened, which indicates that the gain-dispersion effect is lowered under stronger pump. However, the full bandwidth of the spectrum is narrowed, which proves that the spectral filter effect increases and overcomes the effect of self-phase modulation induced spectral broadening. Such a phenomenon was not noticed nor reported before. Our experiment also demonstrates that the pulse interval is highly dependent on the input pump power： with pump power increasing, the pulse interval tends towards more uniform. So our observation qualitatively analyzes the relationship between mode-locked pulse characteristics and input pump power.

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.

Experimental studies of self-starting passive mode locking Er^(3+)-doped fiber ring soliton laser

The mechanism of femtosecond optical pulse generation in a self-starting Er3+ -doped fiber ring soliton laser and experimental research results are discussed. Using the nonlinear polarization rotation effect of the fiber for sat-urable absorbers (and then self-amplitude modulation) which acts as the mode locking mechanism in an Er3+ -doped fiber ring cavity laser, stable self-starting mode locking pulses have been generated. The shortest output pulse is 269 fs, with the central wavelength of 1.531 @m at the repetition rate of 21.37 MHz. The average output powers of the two terminators of the laser are 0.25 mW and 0.08 mW respectively. The threshold pump power which sustains the mode locking is 15 mW. Under high pump power, the laser works in a high order harmonic mode locking state. The mode locking pulse durations vs different cavity lengths are also studied.

Dual-wavelength dissipative soliton operation of an erbium-doped fibre laser using a nonlinear polarization rotation technique

We report on the generation of dual-wavelength dissipative solitons in a passively mode-locked fibre laser with a net normal dispersion using the nonlinear polarization rotation （NPR） technique. Taking the intrinsic advantage of the intracavity birefringence-induced spectral filtering effect in the NPR-based ring laser cavity, the dual-wavelength dissipative solitons are obtained. In addition, the wavelength separation and the lasing location of the dual-wavelength solitons can be flexibly tuned by changing the orientation of the polarization controller.

重频可调谐U波段被动谐波锁模光纤激光器

U波段(1 625~1 675 nm)高重频锁模光纤激光器在甲烷气体检测、扩展通信波段、光子显微镜、眼部手术等领域有广泛的应用前景。基于被动谐波锁模(Harmonic Mode-Locking, HML)的孤子自频移(Soliton Self-Frequency Shift, SSFS)技术是一种实现高重频U波段激光输出的有效方式。首先搭建了基于非线性偏振旋转(Nonlinear Polarization Rotation, NPR)的被动HML光纤激光器,并以此为种子源,通过级联的放大系统将输出功率最高放大至1.7 W。而后将放大的脉冲输入到一段反常色散的色散位移光纤(Dispersion-Shifted Fiber, DSF)中,利用SSFS效应将其中心波长频移至U波段。研究了其中三个重复频率(722.0、941.7、1 224.2 MHz)状态,系统地探究了脉冲重复频率对SSFS的影响。首次使用NPR被动HML光纤激光器作为SSFS效应种子源,实现了波长可覆盖整个U波段范围的GHz脉冲输出。

非线性偏振旋转锁模掺铥光纤激光器的多孤子输出理论研究

本文研究探讨了在非线性偏振旋转锁模掺铥光纤激光器中,孤子分子和类噪声脉冲的演化特性。理论研究表明,当激光器在负色散条件下工作且腔内参数得到恰当配置时,能够稳定产生锁模孤子脉冲。通过细调腔内的偏振状态并适度增加泵浦功率,可以实现孤子分子的输出。继续调整腔内条件,还能够获得类噪声脉冲。泵浦功率和偏振控制器的调整,通过改变腔内增益,成为产生多种多孤子模式的关键因素。这一发现为深入理解负色散区域内2μm波段锁模掺铥光纤激光器产生多孤子动态特性提供了有价值的参考。

Pulse-train nonuniformity in an all-fiber ring laser passively mode-locked by nonlinear polarization rotation

This paper reports the periodic power variation of the pulse-train in a passively mode-locked soliton fiber ring laser. It can obtain either the uniform or nonuniform pulse-train output by simply rotating the polarization controllers. The experimental results show that the pulse-train nonuniformity is caused by the interaction between the nonuniform polarization states of the soliton pulses and the passive polarizer in the cavity.

Two-dimensional materials-decorated microfiber devices for pulse generation and shaping in fiber lasers

Two-dimensional（2D） materials have been regarded as a promising nonlinear optical medium for fabricating versatile optical and optoelectronic devices. Among the various photonic applications, the employment of 2D materials as nonlinear optical devices such as saturable absorbers for ultrashort pulse generation and shaping in ultrafast lasers is one of the most striking aspects in recent years. In this paper, we review the recent progress of 2D materials based pulse generation and soliton shaping in ultrafast fiber lasers, and particularly in the context of 2D materials-decorated microfiber photonic devices. The fabrication of 2D materials-decorated microfiber photonic devices, high performance mode-locked pulse generation, and the nonlinear soliton dynamics based on pulse shaping method are discussed. Finally, the challenges and the perspective of the 2D materials-based photonic devices as well as their applications are also discussed.

Multiple-Pulse Operation in Passively Mode-Locked Fibre Laser with Positive Dispersion Cavity

We report the observation of rectangular shape spectrum in passively mode-locked fibre laser with positive dispersion cavity. The spectrum is broad and flat, and 3dB bandwidth can be up to 17.61 nm. Multiple-pulse operation is observed in our laser system. The spectrum width, pulse energy, pulse width and peak power of the mode-locked laser output change with the appearance of multiple-pulse operation.

Coupled Optical Solitons for Pulse Propagation in Multi-Level Media

We investigate the shape-preserving propagation of N optical pulses in an （N ＋ 1）-level medium. We solve Maxwell-Schroedinger equations exactly and provide several types of explicit coupled soliton solutions, which are temporally amplitude- and group-velocity-matched multi-mode slow-optical pulses of the system.

Two-dimensional relativistic electromagnetic dromion-like soliton in a cold transparent plasma

By using a standard multiple scale method, a Davey-Stewartson （DS） equation has been derived and also applied to a multi-dimensional analytical investigation on the interaction of an ultra-intense laser pulse with a cold unmagnetized transparent electron-ion plasma. The regions of instability are found by considering the modulation instability of a plane wave solution of the DS equation. The DS equation is just of the Davey Stewartson 1 （DS1） type and admits a dromion solution, i.e. a two-dimensional （2D） dromion soliton decaying exponentially in all spatial directions. A 2D relativistic electromagnetic dromion-like soliton （2D REDLS） is derived for a vector potential.

Few-cycle relativistic solitons in plasmas

A set of exact one-dlmensional solutions to coupled nonlinear equations describing the propagation of a relativistic ultrashort circularly polarized laser pulse in a cold collisionless and bounded plasma where electrons have an initial velocity in the laser propagating direction is presented. The solutions investigated here are in the form of quickly moving envelop solitons at a propagation velocity comparable to the light speed. The features of solitons in both underdense and overdense plasmas with electrons having different given initial velocities in the laser propagating direction are described. It is found that the amplitude of solitons is larger and soliton width shorter in plasmas where electrons have a larger initial velocity. In overdense plasmas, soliton duration is shorter, the amplitude higher than that in underdense plasmas where electrons have the same initial velocity.

Standing Ultrashort Relativistic Solitons in Overdense Plasmas

By using a one-dimensional self-consistent relativistic fluid model, an investigation is made numerically on relativistic electromagnetic solitons with a high intensity in cold overdense plasmas with an electrons＇ initial velocity opposite to the laser propagating direction. Two types of standing solitons with zero group velocity are found at the given electrons＇ initial velocities. One is single-humped with a weakly relativistic intensity; the another is multi-humped with a strong relativistic amplitude. The properties of these two types of solitons are presented in detail.

Relativistic Electromagnetic Soliton in Electron-Positron-Ion Plasma

Considering the limiting weak nonlinearity, we obtained the solution of the coupled equations describing the interaction of ultraintense laser with cold transparent multicomponent plasma. It was indicated that the ions tend to accumulate at the center of the soliton and have large velocity when we consider the mobile ions in the multicomponent plasma, which shows that the result is different from that of the Berezhiani＇s analysis. The change of proportion of ions in the plasma has effects on the amplitude of vector potential and the maximum velocity of the soliton.

A Novel Nanotube-Based Fiber Laser for Ultrashort Pulse Generation and Fast Measurements

We propose a nanotube-based erbium-doped fiber laser that can deliver conventional soliton (CS) and stretched pulse (SP) based on D-shaped fiber saturable absorber (DF-SA) where evanescent-field interaction works. The novel Nanotube-based Fiber Laser can generate SP or CS by tuning pump power and polarization controller (PC) properly. The net cavity dispersion of laser is slightly negative. In our experiment, by optimizing the PC in the cavity, CS and SP can be obtained at the central wavelengths of 1530.6 nm and 1530.3 nm due to on carbon nanotubes and the spectral filtering effect induced by nonlinear polarization rotation. Although the acquired CS and SP nearly have the same central wavelengths, they show distinct optical spectra, 3-dB bandwidths. The proposed fiber laser with switchable CS and SP is attractive for ultrashort pulse generation and fast measurements in practical applications.

Effects of Dissipative Terms on Dissipative Soliton Resonance Curve

Dissipative soliton resonance (DSR) is a phenomenon where the energy of a soliton in a dissipative system increases without limit at certain values of the system parameters. Using the method of collective variable approach, we have found an approximate relation between the parameters of the normalized complex cubic-quintic Ginzburg-Landau equation where the resonance manifests itself. Comparisons between the results obtained by collective variable approach, and those obtained by the method of moments show good qualitative agreement. This choice also helps to see the influence of the active terms on the resonance curve, so can be very useful in constructing passively mode-locked laser that generate solitons with the highest possible energies.

纯四次孤子光纤激光器研究进展

纯四次孤子光纤激光器是一种新型的超短脉冲激光器,能够在四阶色散和自相位调制效应平衡下保持脉冲形状稳定传输.相比于二阶色散主导下的常规孤子激光器,纯四次孤子激光器输出的锁模脉冲能量可以高出1-2个数量级,这将为研制高能量、高峰值功率的光纤激光器提供新思路.本文系统地回顾了近年来在光纤激光器等非线性光学系统中纯四次孤子的产生以及传输特性,并探讨了纯四次孤子中已观察到的一些特殊瞬态动力学现象.同时,介绍了笔者所在课题组在该研究方向上的最新成果.最后,本文对纯四次孤子光纤激光器的应用前景以及发展趋势进行展望,为相关领域未来的研究提供有价值的参考.这些结果将有助于更全面认识纯四次孤子光纤激光器的基本物理特性.

基于色散傅里叶变换的孤子脉冲建立与放大研究

基于色散傅里叶变换技术研究了反常色散腔内传统孤子和正常色散腔内耗散孤子建立时的孤子动力学过程。为探究脉冲在光放大器中如何随放大功率演变,实验和模拟研究了这两类孤子经放大器放大后的动态变化。结果表明,这两类孤子的光谱在建立时会经历不同的振荡过程,传统孤子光谱会由能量有剧烈振荡的调制拍频状态过渡至稳定,耗散孤子光谱则会由无序调制状态平稳展宽至稳定。在放大器中,随着放大器泵浦功率的上升,传统孤子光谱中心能量将被转移而展宽,耗散孤子光谱则在保持谱宽不变的情况下在边沿出现尖峰。这些锁模光纤激光器和光放大器中的动态孤子非线性现象在超快激光及其放大系统中有着潜在的应用价值。