Breathing spatial solitons in non-Kerr media.

The concept of soliton internal mode is introduced to explain quantitatively the long-lived oscillations of self-guided beams, or breathing spatial solitons. Cubic-quintic nonlinearity is considered in detail, and it is shown that the existence of the internal mode affects strongly the beam propagation in non-Kerr media, leading to oscillatory dependence of the output width of the beam versus its input power.

Effect of third-order dispersion on dark solitons.

Third-order dispersion has a detrimental effect on dark solitons, leading to resonant generation of growing soliton tails and soliton decay. This effect is shown to be much stronger than that for bright solitons.

Incoherently coupled dark-bright photorefractive solitons.

We report the observation of incoherently coupled dark-bright spatial soliton pairs in a biased bulk photorefractive crystal. When such a pair is decoupled, the dark component evolves into a triplet structure, whereas the bright one decays into a self-defocusing beam.

Drift instability of dark solitons in saturable media.

It is shown that dark solitons display an inherent instability for a strong saturation of the nonlinear refractive index provided that the background intensity exceeds a certain critical value. Such an instability manifests itself as a drift of a black soliton that transform into a gray soliton and radiation.

Soliton interaction and bound states in amplified-damped fiber systems.

It is shown that the soliton interaction can be signif icantly reduced in a system with ultimately stable soliton propagation. Moreover, under the action of strong filtering and nonlinear gain the soliton interaction can change sign from attraction to repulsion and vice versa. The formation of in-phase and out-of-phase bound states is also demonstrated.

Soliton singularity in the system with nonlinear gain.

Solitons propagating in a system with spectral filtering, being nonlinearly stable, suffer from the growth of linear radiation. This effect can be partially overcome by the use of nonlinear gain. I analyze steady-state soliton propagation in such a system and reveal unexpected the singularity of the soliton amplitude.

Soliton polarization rotation in fiber lasers.

I have found the approximate analytical solution in explicit form for a vector soliton with an arbitrary component ratio. My solution describes the dependence of soliton intensity on polarization angle and also nonlinear polarization rotation. The analytical results agree well with the numerical simulations.

Increased amplifier spacing in a soliton system with quantum-well saturable absorbers and spectral filtering.

The spacing between optical amplifiers in a long-haul soliton system may be increased to 100 km by using only passive quantum-well saturable absorbers and narrow-band filters for soliton control. After transmission over 9000 km at 10 Gbits/s, the effects of soliton-soliton interaction and Gordon-Haus jitter in the proposed systemyield bit error rates of better than 10(-9).

Soliton interaction in the presence of a weak nonsoliton component.

We study both experimentally and theoretically soliton interaction in the presence of a weak nonsoliton component and show that the existence of a frequency-shifted cw wave results in a temporal shift of the soliton.

Interpretation of the effect of reduction of soliton interaction by bandwidth-limited amplification.

The effect of reduction of soliton interaction by bandwidth-limited amplification is analyzed by numerical solution of the nonlinear Schrödinger equation, by computing the eigenvalues of inverse-scattering transform, and by solving the equation for a soliton center. It is shown that this effect is explained by the influence of the perturbation on soliton central frequency.

Amplification of femtosecond pulses in a passive, all-fiber soliton source.

We report a theoretical and experimental study of the amplification of femtosecond soliton pulses generated by a passively mode-locked fiber laser in a high-gain erbium-doped fiber amplifier (EDFA). Results on the spectral and temporal evolution of 450-fs soliton pulses propagating within an EDFA are presented. Power gains as high as 30 dB and the generation of sub-100-fs Raman colored solitons are observed.

Decay of dark solitons due to the stimulated Raman effect.

It is demonstrated analytically and numerically that dark solitons always disappear owing to the stimulated Raman effect. Instead of dark solitons, the stable propagation of optical kinks on the cw background in the region of the normal group-velocity dispersion is possible.