Anomalous Dispersion Fiber Research Articles

Intermittent burst of a super rogue wave in the breathing multi-soliton regime of an anomalous fiber ring cavity.

We report the intermittent burst of a super rogue wave in the multi-soliton (MS) regime of an anomalous-dispersion fiber ring cavity. We exploit the spatio-temporal measurement technique to log and capture the shot-to-shot wave dynamics of various pulse events in the cavity, and obtain the corresponding intensity probability density function, which eventually unveils the inherent nature of the extreme events encompassed therein. In the breathing MS regime, a specific MS regime with heavy soliton population, the natural probability of pulse interaction among solitons and dispersive waves exponentially increases owing to the extraordinarily high soliton population density. Combination of the probabilistically started soliton interactions and subsequently accompanying dispersive waves in their vicinity triggers an avalanche of extreme events with even higher intensities, culminating to a burst of a super rogue wave nearly ten times stronger than the average solitons observed in the cavity. Without any cavity modification or control, the process naturally and intermittently recurs within a time scale in the order of ten seconds.

Experimental spatio-temporal analysis on the shot-to-shot coherence and wave-packet formation in quasi-mode-locked regimes in an anomalous dispersion fiber ring cavity

We carry out systematic and dedicated experimental investigations on the shot-to-shot coherence and wave-packet formation in quasi-mode-locked (QML) regimes, including noise-like-pulse, symbiotic, and multi-soliton regimes in an anomalous-dispersion fiber ring cavity. To analyze the regimes in real-time, we take advantage of the spatio-temporal shot-to-shot measurement technique. We show that the individual regimes exhibit significantly different coherence characteristics, depending not only on the amount of nonlinear phase shift accumulated per roundtrip but also on the degree of soliton interaction, the latter of which crucially governs the bunching (i.e., the wave-packet formation) or anti-bunching mechanisms in the corresponding QML regimes. In fact, solitons with higher intensities tend to undergo higher nonlinear phase shift and stronger soliton interactions. Subsequently, the intensified soliton interactions among the individual solitons in the multi-soliton-regime cavity trigger them to form a bunched soliton-group, i.e., a wave packet, thereby resulting in QML pulses in the noise-like pulse or symbiotic regime. This complicated nonlinear process, in turn, causes a severe degradation in the shot-to-shot coherence of the resultant QML pulses. In addition, the shot-to-shot coherence trends observed in the experiment are in good agreement with our previous numerical predictions, so that the strong correlation between the shot-to-shot coherence of QML pulses and the corresponding nonlinear phase shift accumulated per roundtrip is confirmed by this experimental observation.

Molecular and vectorial properties of the vector soliton molecules in anomalous-dispersion fiber lasers

Through thorough numerical simulations, we investigated the molecular and polarization properties of the vector soliton molecules in an anomalous-dispersion fiber laser for the first time to our best knowledge. The molecular properties of the fast and slow modes of the vector soliton molecule can have different evolution characteristics on the interaction plane. The polarization dynamics of the leading and trailing vector pulses of the vector soliton molecule can have different evolution dynamics on the polarization Poincare sphere. The balance between gain and loss, the coupling between the orthogonal components and the interaction between the leading and trailing pulses result in various physical pictures of the vector soliton molecules in fiber lasers. Our results enrich the vector soliton dynamics in fiber lasers and have potential in optical signal processing and polarization division multiplexing for optical communications.

Numerical study on multi-pulse dynamics and shot-to-shot coherence property in quasi-mode-locked regimes of a highly-pumped anomalous dispersion fiber ring cavity.

We numerically investigate quasi-mode-locked (QML) multi-pulse dynamics in a fiber ring laser cavity in the anomalous dispersion regime. We show that the laser cavity can operate in five constitutively different QML regimes, depending on the saturation power of the saturable absorber element and the length of the passive fiber section that parameterize the overall nonlinearity and dispersion characteristic of the laser cavity. We classify them into the incoherent noise-like-pulse, partially-coherent noise-like-pulse, symbiotic, partially-coherent multi-soliton, and coherent multi-soliton regimes, accounting for their coherence and multi-pulse formation features. In particular, we numerically clarify and confirm the symbiotic regime for the first time to the best of our knowledge, in which noise-like pulses and multi-solitons coexist stably in the cavity that has recently been observed experimentally. Furthermore, we analyze the shot-to-shot coherence characteristics of the individual QML regimes relative to the amount of the nonlinear-phase shift per roundtrip, and verify a strong correlation between them. We also show that the net-cavity dispersion plays a critical role in determining the multi-pulse dynamics out of the partially-coherent noise-like-pulse, symbiotic, and partially-coherent multi-soliton regimes, when the cavity bears moderate nonlinearity. We quantify and visualize all those characteristics onto contour maps, which will be very useful and helpful in discussing and clarifying the complex QML dynamics.

Roadmap to high-energy square pulses in anomalous dispersion fiber lasers

Dissipative soliton resonance (DSR) is a soliton formation where the energy in a dissipative system becomes infinite. In the anomalous dispersion regime, this energy is not limited by the soliton area theorem. Since this phenomenon is wave breaking free, it can be useful in designing fiber lasers generating pulses with relatively high energies. Based on this principle, we have demonstrated the emission of high energetic square pulses from Er:Yb double-clad passively mode-locked fiber lasers using different mode-locking mechanisms. We first show the evolution of pulse width, energy and peak power by varying the pumping power of the amplifier, then we control separately the characteristic of the output square pulse by assigning each one to an amplifier. Experimental results exhibit record energies in fiber lasers up to 10 uJ. Full Text: PDF ReferencesW. Chang, A. Ankiewicz, J.M Soto Crespo and N. Akhmediev, " Dissipative soliton resonances", Phys. Rev. A 78, 023830 (2008). CrossRef P. Grelu, W. Chang, A. Ankiewicz, J. M. Soto-Crespo, and N. Akhmediev, "Dissipative soliton resonance as a guideline for high-energy pulse laser oscillators", J. Opt. Soc. Am. B 27, 2336 (2010). CrossRef X. Wu, D. Y. Tang, H. Zhang, and L. M. Zhao, "Dissipative soliton resonance in an all-normal-dispersion erbium-doped fiber laser", Opt. Express 17, 5580 (2009). CrossRef G. Semaan, F. Ben Braham, M. Salhi, Y. Meng, F. Bahloul, and F. Sanchez, "Generation of high energy square-wave pulses in all anomalous dispersion Er:Yb passive mode locked fiber ring laser", Opt. Express 24, 8399 (2016). CrossRef K. Krzempek, "Dissipative soliton resonances in all-fiber Er-Yb double clad figure-8 laser", Opt. Express 23, 30651 (2015). CrossRef L. Mei et al., "Width and amplitude tunable square-wave pulse in dual-pump passively mode-locked fiber laser", Opt. Lett. 39, 3235 (2014). CrossRef X. Zhang et al., "Square-wave pulse with ultra-wide tuning range in a passively mode-locked fiber laser", Opt. Lett. 37, 1334 (2012). CrossRef K. Krzempek, J. Sotor, and K. Abramski, "Compact all-fiber figure-9 dissipative soliton resonance mode-locked double-clad Er:Yb laser", Opt. Lett. 41, 4995-4998 (2016). CrossRef G. Semaan, F. Ben Braham, J. Fourmont, M. Salhi, F. Bahloul, and F. Sanchez, "10uJ dissipative soliton resonance square pulse in a dual amplifier figure-of-eight double-clad Er:Yb mode-locked fiber laser", Opt. Lett. 41, 4767 (2016). CrossRef K. Krzempek and K. Abramski, "Dissipative soliton resonance mode-locked double clad Er:Yb laser at different values of anomalous dispersion", Opt. Express 24, 22379-22386 (2016). CrossRef

Er-doped mode-locked fiber laser with WS2/fluorine mica (FM) saturable absorber

The report presents conventional soliton operation in an anomalous-dispersion fiber laser with a novel WS2 saturable absorber (SA) based on fluorine mica (FM) substrate. Compared to organic host material such as polymer composite, FM has higher softening temperature, heat dissipation and laser damage threshold. In this work, the modulation depth (MD) and non-saturable loss (NL) of WS2/FM SA are measured to be 3.1% and 15%, respectively. By employing the SA, a stable conventional soliton mode-locked fiber laser is achieved. The repetition rate is 8.2MHz and the pulse duration is 830fs. The fiber laser works in mode locking operation for at least ten days and no damage of the SA is observed. The results indicate that WS2/FM material is an ideal SA for Er-doped fiber (EDF) lasers.

Characterization of optical rogue wave based on solitons' eigenvalues of the integrable higher-order nonlinear Schrödinger equation

The dynamics of the optical rogue wave phenomenon in the framework of integrable higher-order nonlinear Schrödinger equation (HNLSE) including the third order dispersion term is presented in this paper. When rogue waves generate through soliton collision, the colliding solitons' eigenvalues of the associated equation of HNLSE should be constant in the vicinity of rogue wave generation. Our results reveal that soliton collision is one of the generation mechanisms of optical rogue waves in anomalous dispersion fiber by taking the third order dispersion into consideration in the HNLSE based model.

WS2/fluorine mica (FM) saturable absorber for high power optical pulse formation

The report presents the high power mode-locking operation in an anomalous-dispersion fiber laser with a novel WS2 saturable absorber (SA) based on fluorine mica (FM) substrate. Compared to organic host material such as polymer, FM has higher softening temperature, heat dissipation and laser damage threshold. By employing the SA, a stable mode-locked fiber laser is achieved. The duration of the pulse broadens from 2.816ns to 3.654ns almost linearly with increasing pump power. The average output power and single pulse energy can increase up to 33.5mW and 4 nJ at the maximum pump power respectively. The results indicate that WS2/FM material is an ideal SA for high power Er-doped fiber (EDF) lasers.

Spectral Compression of a Dispersion-Managed Mode-Locked Tm:Fiber Laser at $1.9~\mu \text{m}$

We demonstrate self-phase modulation (SPM)-based spectral compression of the pulse from an all-fiber dispersion-managed Thulium (Tm)-doped fiber laser at 1.9 $\mu \text{m}$ . The laser consists of ultrahigh numerical aperture fiber for the dispersion management to avoid soliton mode-locking and is mode-locked by nonlinear amplified loop mirror. Spectrum of the pulse is compressed from 7 to 3 nm by SPM in an anomalous dispersion core-pumped Tm-doped fiber, together with a passive fiber. Numerical simulations agree well with the experimental results. Limitation of high-efficiency spectral compression due to soliton evolution in the anomalous dispersion fibers is also discussed.

Parabolic and semiparabolic pulse dynamics in optical fibers

Nonlinear pulse dynamics in two stages of different active or passive fibers are investigated in this work. Numerical approach of the symmetrized split step Fourier method is used to solve the nonlinear Schrödinger equation in the presence of fiber gain, nonlinearity, and dispersion. An input Gaussian pulse evolves into a linearly chirped perfect parabolic pulse (PP) when it propagates through a standard normal dispersion decreasing fiber amplifier. At the same time, for an erbium-doped dispersion decreasing fiber amplifier with a similar dispersion variation with length, the semiparabolic pulse (SPP) is produced at the output end of the fiber. To our knowledge, this is shown for the first time. In second stage, the so-obtained perfect PP, SPP, and also a chirp-free perfect PP are fed into the input of several normal dispersion fibers and the comparative pulse evolution is studied in detail with the variations of dispersion coefficient, gain, and nonlinearity. While using these pulses as the input of an anomalous dispersion fiber, our result shows that the linearly chirped PP is most efficient for compressing the pulses with a good quality factor without dropping significant pedestal energy.

Soliton's eigenvalue based analysis on the generation mechanism of rogue wave phenomenon in optical fibers exhibiting weak third order dispersion.

One of the extraordinary aspects of nonlinear wave evolution which has been observed as the spontaneous occurrence of astonishing and statistically extraordinary amplitude wave is called rogue wave. We show that the eigenvalues of the associated equation of nonlinear Schrödinger equation are almost constant in the vicinity of rogue wave and we validate that optical rogue waves are formed by the collision between quasi-solitons in anomalous dispersion fiber exhibiting weak third order dispersion.

Femtosecond pulse generation from a topological insulator mode-locked fiber laser

We reported on the generation of femtosecond pulse in a fiber ring laser by using a polyvinyl alcohol (PVA)-based topological insulator (TI), Bi2Se3 saturable absorber (SA). The PVA-TI composite has a low saturable optical intensity of 12 MW/cm2 and a modulation depth of ~3.9%. By incorporating the fabricated PVA-TISA into a fiber laser, mode-locking operation could be achieved at a low pump threshold of 25 mW. After an optimization of the cavity parameters, optical pulse with ~660 fs centered at 1557.5 nm wavelength had been generated. The experimental results demonstrate that the PVA could be an excellent host material for fabricating high-performance TISA, and also indicate that the filmy PVA-TISA is indeed a good candidate for ultrafast saturable absorption device.

High-energy femtosecond 2-μm fiber laser

We describe in detail a high energy, high power ultrafast thulium-doped fiber laser system. The pulse energy of 156 μJ was realized. The laser system is comprised of a mode-locked 2020-nm seed oscillator and multiple-stage power/energy amplifiers. The seed oscillator output pulses at a repetition rate of 2.5 MHz. The seed pulses were stretched with the anomalous dispersion fiber to the duration of 320 ps. An acousto-optic modulator was used as a pulse picker to lower the repetition rate. A two-stage preamplifier was used to boost the pulse energy to 3 μJ. The pulse energies of up to 156 μJ and the average power of 15.6 W were obtained from the final stage of power amplifier at a repetition rate of 100 kHz with a slope efficiency of 26%. The pulse durations of 780 fs were obtained after pulse compression. High optical signal-to-noise ratio (OSNR) and low background noise were also achieved at this low repetition rate.

High-quality optical pulse train generator based on solitons on finite background

We report a simple method to exploit the typical properties of solitons on a finite background in order to generate high-repetition-rate and high-quality optical pulse trains. We take advantage of the nonlinear evolution of a modulated continuous wave toward localized structures upon a nonzero background wave in anomalous dispersive fiber. After a stage of nonlinear compression, a delay-line interferometer enables the annihilation of the finite background and simultaneously allows the repetition-rate doubling of the pulse train.

Fiber-based device for the detection of low-intensity fluctuations of ultrashort pulses

We describe a fiber-based device that can significantly enhance the low-intensity fluctuations of an ultrashort pulse train to detect them more easily than with usual direct detection systems. Taking advantage of the Raman intrapulse effect that progressively shifts the central frequency of a femtosecond pulse propagating in an anomalous dispersion fiber, a subsequent spectral filtering can efficiently increase the level of fluctuations by more than 1 order of magnitude. We show that attention has to be paid to maintain the shape of the statistical distribution unaffected by the nonlinear process.

One stage pulse compression at 1554nm through highly anomalous dispersive photonic crystal fiber

We demonstrate the pulse compression at 1554 nm using one stage of highly anomalous dispersive photonic crystal fibers with a dispersion value of 600 ps/nm∙km. A 1.64 ps pulse is compressed down to 0.357 ps with a compression factor of 4.6, which agrees reasonably well with the simulation value of 6.1. The compressor is better suited for high energy ultra-short pulse compression than conventional low dispersive single mode fibers.

Dispersion-insensitive low-coherent pulses emerging from nonlinear polarization switching

We have experimentally investigated low-repetition nanosecond pulses delivered from an erbium-doped fiber (EDF) laser operating in ultra-large anomalous dispersion regime. The output pulses with rectangular profile and Gaussian spectrum almost keep invariable when they propagate through either normal- or anomalous-dispersion fibers. After nanosecond pulses are amplified via a two-stage EDF amplifier, they are broken up and exhibited as flatly broadened supercontinuum from 1520 to 1700 nm if amplified pulses are launched into a 10-km single-mode fiber, whereas the pulses retain the same duration with a broadband supercontinuum from 1200 to 1750 nm if they are input into a 100-m highly-nonlinear low-dispersion photonic-crystal fiber (PCF). The experimental observations demonstrate that the nanosecond pulses result from nonlinear polarization switching and can be regarded as dispersion-insensitive low-coherent pulses rather than compressible pulses.

Soliton formation and evolution in passively-mode-locked lasers with ultralong anomalous-dispersion fibers

The soliton formation and evolution are numerically and experimentally investigated in passively-mode-locked lasers where pulses encounter ultralong anomalous-dispersion fibers. The pulse formation and evolution in lasers are determined by two balances, namely, nonlinearity and anomalous-dispersion balance and intracavity filtering and self-amplitude modulation balance. It is numerically found that a higher-energy soliton can be split into identical lower-energy multisolitons with exactly the same physical properties. Simulation results show that the separation of neighboring solitons is variational in the temporal domain. The temporal and spectral characteristics of solitons have large variations throughout the laser cavity, qualitatively distinct from the steady state of conventional solitons. The experimental observations confirm the theoretical predictions.

Measurement of Residual Chromatic Dispersion or OSNR via Nonlinear Spectral Evolution

In this work, we report a new fiber architecture providing high accuracy measurements of both residual chromatic dispersion and optical signal-to-noise ratio. Taking advantage of the nonlinear spectral evolution of pulses propagating in a Kerr medium, we have numerically and experimentally validated the use an anomalous dispersive fiber combined with a central spectral filtering.

Ultrafast stretched-pulse fiber laser mode-locked by carbon nanotubes

Ultrafast fiber sources having short pulses, broad bandwidth, high energy, and low amplitude fluctuations have widespread applications. Stretched-pulse fiber lasers, incorporating segments of normal and anomalous dispersion fibers, are a preferred means to generate such pulses. We realize a stretched-pulse fiber laser based on a nanotube saturable absorber, with 113 fs pulses, 33.5 nm spectral width and ˜0.07% amplitude fluctuation, outperforming current nanotube-based designs.