Formation Of Dissipative Solitons Research Articles

On the thermal dissipation in the thermomechanical treatment of metal materials

The results of plastic compression of steels and alloys of different chemical compositions at temperatures and rates of plastic deformation corresponding to common thermomechanical treatment (TMT) regimes are considered. The features of the diagrams σ (ε, έ, Т) are revealed. The processes of strain accumulation and thermal dissipation are accompanied by structural rearrangements. Depending on the chemical composition and hot compression modes, structural transformations occur self-organized, with the possibility of excitation of oscillations and the formation of dissipative solitons.

Intrinsic polarization conversion and avoided-mode crossing in X-cut lithium niobate microrings

Compared with well-developed free space polarization converters, polarization conversion between TE and TM modes in the waveguide is generally considered to be caused by shape birefringence, like curvature, morphology of waveguide cross section and scattering. Here, we study the polarization conversion mechanism in 1-THz-FSR X-cut lithium niobate microrings with multiple-resonance condition, that is the conversion can be implemented by birefringence of waveguides, which will also introduce an avoided-mode crossing. In the experiment, we find that this mode crossing results in severe suppression of one sideband in local nondegenerate four-wave mixing and disrupts the cascaded four-wave mixing on this side. Simultaneously, we propose one two-dimensional method to simulate the eigenmodes (TE and TM) in X-cut microrings, and the mode crossing point. This work will provide one approach to the design of polarization converters and simulation for monolithic photonics integrated circuits, and may be helpful to the studies of missed temporal dissipative soliton formation in X-cut lithium niobate rings.

Transient dynamics of dissipative solitons formation in a net-normal dispersion mode-locked fiber laser based on nonlinear polarization evolution.

In mode-locked fiber lasers, the formation of ultrashort pulses from noisy or unstable states is a crucial area of research. Investigating these complex nonlinear dynamics can lead to valuable insights and new practical engineering techniques, particularly for the design and optimization of optical systems. Time-stretch dispersive Fourier transform, utilized in our study to investigate dissipative solitons formation in a net-normal dispersion nonlinear polarization evolution mode-locked fiber laser, provides a window into the intricate dynamics of such systems. In our experiments, the identification of five distinct transient stages in the formation process sheds light on the underlying mechanisms of dissipative soliton (DS) formation. The five distinct transient stages involved in the formation process include relaxation oscillation, modulation instability, spectral broadening, soliton explosions (SEs), and stable mode-locking. Notably, we also observed the generation of dissipative rogue waves during the SE stage. Our findings shed light on the intricate dynamics of DS formation and offer valuable insights for the design and optimization of mode-locked fiber lasers.

Energy scaling of an erbium-doped mode-locked fiber laser oscillator

We investigate a promising approach to the energy scaling of mode-locked erbium fiber lasers. It consists in a special cavity design, comprised of a really long polarization maintaining (PM) part and a short non-PM part. Two separate fiber parts ensure the principle of space division for highly chirped dissipative soliton formation and NPE-based self-amplitude modulation effects. As a result, the pulse energy was increased up to 4 nJ with an estimated transform-limited pulse duration of 150 fs. It was also found that further energy scaling is limited by transition to a noise-like pulse generation regime. Numerical simulations revealed that this transition is associated with a contrast of the employed spectral filter and the amplifier noise level, which agrees well with the experiment.

Real-time observation of dissipative solitons formation and breaking dynamics in a mode-locked fiber laser

The formation and breaking dynamics of dissipative solitons (DSs) are observed in a passive mode-locked fiber laser using dispersive Fourier transform technique. Q-switched instabilities are observed both in the formation of DS and the transition breaking dynamics of DSs on gradually increasing the pump power. The real time temporal and spectral dynamics of the entire dynamics are discussed. The generation of the Q-switched instabilities could be attributed to the weak pulse energy before reaching the stable soliton state. These findings would facilitate an in-depth understanding of the formation and breaking dynamics of DSs.

Experimental revealing of asynchronous transient-soliton buildup dynamics

The buildup process of coherent structures and patterns from the composite balance between conservative and dissipative effects is a universal phenomenon that occurs in various areas of physics, ranging from quantum mechanics to astrophysics. Dissipative solitons are highly coherent solutions of nonlinear wave equations, and provide an excellent research platform for ultrafast transient phenomena. Herein, by taking advantage of the fast detection technique provided by the dispersive Fourier transform, we experimentally observe the spectral broadening and breathing behavior of transient dissipative structures produced asynchronously during the buildup process of dissipative solitons. These observations unveil a novel dynamics of dissipative soliton generation, which is accompanied by energy quantization, self-phase modulation induced spectral broadening, structural dissipative soliton formation, and Raman soliton self-frequency shifting, thus providing a new insight in transient ultrafast laser dynamics.

Edge and bulk dissipative solitons in modulated PT-symmetric waveguide arrays.

We address dissipative soliton formation in modulated parity-time (PT)-symmetric continuous waveguide arrays composed from waveguides with amplifying and absorbing sections, whose density gradually increases (due to decreasing waveguide separation) either towards the center of the array or towards its edges. In such a structure, the level of gain/loss at which PT-symmetry gets broken depends on the direction of increase of waveguide density. Breakup of PT-symmetry occurs when eigenvalues of modes localized in the region where waveguide density is largest collide and move into a complex plane. In this regime of broken symmetry, the inclusion of focusing Kerr-type nonlinearity of the material and weak two-photon absorption allows to arrest the growth of amplitude of amplified modes and may lead to the appearance of stable attractors either in the center or at the edge of the waveguide array, depending on the type of array modulation. Such solitons can be stable; they acquire specific triangular shapes and notably broaden with increase of gain/loss level. Our results illustrate how spatial array modulation that breaks PT-symmetry "locally" can be used to control the specific location of dissipative solitons forming in the array.

Temporal solitons in free-space femtosecond enhancement cavities

Temporal dissipative solitons in nonlinear optical resonators are self-compressed, self-stabilizing and indefinitely circulating wave packets. Owing to these properties, they have been harnessed for the generation of ultrashort pulses and frequency combs in active and passive laser architectures, including mode-locked lasers1–4, passive fibre resonators5 and microresonators6–11. Here, we demonstrate the formation of temporal dissipative solitons in a free-space enhancement cavity with a Kerr nonlinearity and a spectrally tailored finesse. By locking a 100-MHz-repetition-rate train of 350-fs, 1,035-nm pulses to this cavity-soliton state, we generate a 37-fs sech²-shaped pulse with a peak-power enhancement of 3,200, which exhibits low-frequency intensity-noise suppression. The power scalability unique to free-space cavities, the unprecedented combination of peak-power enhancement and temporal compression, and the cavity-soliton-specific noise filtering attest to the vast potential of this platform of optical solitons for applications including spatiotemporal filtering and compression of ultrashort pulses and cavity-enhanced nonlinear frequency conversion. Temporal dissipative soliton formation in a free-space femtosecond enhancement cavity with a thin Kerr medium is reported. Locking a 350-fs, 1,035-nm pulse train with a repetition rate of 100 MHz to this cavity-soliton state generates a 37-fs sech2-shaped pulse with a peak-power enhancement of 3,200.

Real-time observation of dissipative soliton formation in nonlinear polarization rotation mode-locked fibre lasers

Formation of coherent structures and patterns from unstable uniform state or noise is a fundamental physical phenomenon that occurs in various areas of science ranging from biology to astrophysics. Understanding of the underlying mechanisms of such processes can both improve our general interdisciplinary knowledge about complex nonlinear systems and lead to new practical engineering techniques. Modern optics with its high precision measurements offers excellent test-beds for studying complex nonlinear dynamics, though capturing transient rapid formation of optical solitons is technically challenging. Here we unveil the build-up of dissipative soliton in mode-locked fibre lasers using dispersive Fourier transform to measure spectral dynamics and employing autocorrelation analysis to investigate temporal evolution. Numerical simulations corroborate experimental observations, and indicate an underlying universality in the pulse formation. Statistical analysis identifies correlations and dependencies during the build-up phase. Our study may open up possibilities for real-time observation of various nonlinear structures in photonic systems.

Passive mode locking and formation of dissipative solitons in electron oscillators with a bleaching absorber in the feedback loop

The mechanisms of passive mode locking and formation of ultrashort pulses in microwave electron oscillators with a bleaching absorber in the feedback loop have been analyzed. It is shown that in the group synchronism regime in which the translational velocity of particles coincides with the group velocity of the electromagnetic wave, the pulse formation can be described by the equations known in the theory of dissipative solitons. At the same time, the regimes in which the translational velocity of electrons differs from the group velocity and the soliton being formed and moving along the electron beam consecutively (cumulatively) receives energy from various electron fractions are optimal for generating pulses with the maximal peak amplitudes.

Smooth and flat phase-locked Kerr frequency comb generation by higher order mode suppression.

High-Q microresonator is perceived as a promising platform for optical frequency comb generation, via dissipative soliton formation. In order to achieve a higher quality factor and obtain the necessary anomalous dispersion, multi-mode waveguides were previously implemented in Si3N4 microresonators. However, coupling between different transverse mode families in multi-mode waveguides results in periodic disruption of dispersion and quality factor, and consequently causes perturbation to dissipative soliton formation and amplitude modulation to the corresponding spectrum. Careful choice of pump wavelength to avoid the mode crossing region is thus critical in conventional Si3N4 microresonators. Here, we report a novel design of Si3N4 microresonator in which single-mode operation, high quality factor, and anomalous dispersion are attained simultaneously. The novel microresonator is consisted of uniform single-mode waveguides in the semi-circle region, to eliminate bending induced mode coupling, and adiabatically tapered waveguides in the straight region, to avoid excitation of higher order modes. The intrinsic quality factor of the microresonator reaches 1.36 × 106 while the group velocity dispersion remains to be anomalous at −50 fs2/mm. With this novel microresonator, we demonstrate that broadband phase-locked Kerr frequency combs with flat and smooth spectra can be generated by pumping at any resonances in the optical C-band.

Influence of gain dynamics on dissipative soliton interaction in the presence of a continuous wave

We investigate the effect of the gain dynamics on the motion and interactions of solitons in the frame of a complex Ginzburg-Landau-type model, which accounts for dissipative soliton formation and propagation in a ring fiber laser. It is shown that the gain dynamics modifies the soliton velocity and their interactions. In the presence of an injected continuous wave, an initial crystal of a few solitons gets broken, either into bunches or into individual solitons. Quasielastic collisions analogous to Newton's cradle have been seen. The soliton set may evolve into gas, solitons, or harmonic mode-locked patterns. The time jitter present in the last situation has been considered.

Dissipative soliton protocols in semiconductor microcavities at finite temperatures

We consider exciton polaritons in a semiconductor microcavity with a saturable absorber in the growth direction of the heterostructure. This feature promotes additional nonlinear losses of the system with the emergence of bistability of the condensate particles number on the nonresonant (electrical or optical) excitation intensity. Furthermore, we demonstrate a new type of bright spatial dissipative exciton-polariton soliton which emerges in the equilibrium between the regions with different particle density. We develop protocols of soliton creation and destruction. The switch to a solitonlike behavior occurs if the cavity is exposed by a short strong laser pulse with certain energy and duration. We estimate the characteristic times of soliton switch on and off and the time of return to the initial cycle. In particular, we demonstrate surprising narrowing of the spatial profile of the soliton and its vanishing at certain temperature due to interaction of the system with the thermal bath of acoustic phonons. We also address the role of polariton-polariton interaction (Kerr-like nonlinearity) on formation of dissipative solitons and show that the soliton may exist both in its presence and its absence.

Control of dissipative solitons in a waveguide trap

A planar package of waveguides with heterogeneously implanted impurity resonance atoms is considered. The conditions of formation of dissipative solitons due to a competition of Kerr saturating nonlinearity and diffraction in the waveguide traps formed by impurity media are determined. It is shown that applying a constant electric field to an impurity resonance medium with a constant dipole moment makes it possible to control the propagation of solitons in Y-shaped waveguide traps.

Femtosecond Fiber Lasers Based on Dissipative Processes for Nonlinear Microscopy.

Recent progress in the development of femtosecond-pulse fiber lasers with parameters appropriate for nonlinear microscopy is reviewed. Pulse-shaping in lasers with only normal-dispersion components is briefly described, and the performance of the resulting lasers is summarized. Fiber lasers based on the formation of dissipative solitons now offer performance competitive with that of solid-state lasers, but with the benefits of the fiber medium. Lasers based on self-similar pulse evolution in the gain section of a laser also offer a combination of short pulse duration and high pulse energy that will be attractive for applications in nonlinear bioimaging.

Dissipative formation of hole-like excitation in ion-acoustic plasma

A viscous plasma is analyzed by reductive perturbation theory to model dissipative soliton formation. A nonlinear Schrodinger equation with complex coefficients is derived. Such an equation can be exactly solved by the technique due to Hirota. Three types of solution can be obtained under different physical conditions: solitary waves, ion-acoustic holes, and shocks. Even in the presence of a dissipative effect like viscosity, it is possible to obtain a solitary-wave-like excitation.