"Fiber fuse" phenomenon

A one-dimensional model governing the propagation of heat waves ("fiber fuse") in an optical fiber is proposed. The model has solutions in the form of high temperature localized waves moving towards the input end of the fiber, fueled by the laser power. These waves can be ignited by local heating at any point along the fiber. The effect of such a wave is irreversible damage to the fiber core. The phenomenon was observed earlier by Hand and Russell, when locally heating a fiber through which CW light of modest intensity was propagating. This induced self-destruction of the optical fiber core.

The results of this study can be found in:

N. Akhmediev, P. St. J. Russell, M. Taki and J. M. Soto-Crespo, Heat dissipative solitons in optical fibers , Physics Letters A 372, 1531 - 1534 (2008).

Strongly Asymmetric Soliton Explosions (theory and numerical simulations)

Asymmetric soliton explosions occur in dissipative systems modeled by the one dimensional complex cubic quintic Ginzburg-Landau CGLE equation. The explosions occur at one side of the soliton in spite of the fact that the initial conditions and the equation itself are symmetric From one explosion to the next the side of the soliton where it occurs alternates so that left and right hand sides of the soliton explode successively. This effect can be explained using the linear stability analysis of the unstable soliton. The transition from the stationary soliton into the exploding one is considered a three stage process of soliton cooling.

The results of this study can be found in:

N. Akhmediev, J. M. Soto-Crespo, Strongly Asymmetric Soliton Explosions, Physical Review E 70, 036613 (2004).

Movie

Dissipative solitons in action (theory and experiment)

This oscillogram shows the output of a passively mode-locked fiber laser with three solitons in the cavity. The largest peak is identified as a soliton pair, whereas the smaller peak is identified as a single soliton. As the single soliton moves with velocity that is different from the velocity of the pair they have to collide. In every collision one soliton is exchanged as shown in the theoretical figure below. The relative motion and the sequence of collisions can be stable for hours once obtained.

The results of this study can be found in:

Ph. Grelu and N. Akhmediev, Group interactions of dissipative solitons in a laser cavity: the case of 2+1, Optics Express, 12, No 14, 3184-3189 (2004).

Discrete Complex quintic Ginzburg-Landau Equation

We study, analytically, the discrete complex cubic-quintic Ginzburg-Landau (dCCGL) equation with nonlocal quintic term. We find a set of exact solutions which includes as particular cases periodic solutions in terms of elliptic Jacobi functions, bright and dark soliton solutions, and constant magnitude solutions with phase shifts. We discuss the common features of these solutions and solutions of the continuous complex Ginzburg-Landau model and solutions of Hamiltonian discrete systems and also their differences.

The results of this study can be found in:

K. Maruno, A. Ankiewicz, and N. Akhmediev, Exact localized and periodic solutions of the discrete complex Ginzburg-Landau equation'', Optics Communications, 221, 199-209 (2003).

Soliton explosions in the experiment

Ti:sapphire mode-locked lasers can operate in a regime in which they intermittently produce exploding solitons. This happens when the laser operates near a critical point. Explosions happen spontaneously, but external perturbations can trigger them. In stable operation, all explosions have similar features, but are not identical. The characteristics of the explosions depend on the intracavity dispersion. This figure shows typical experimental data for soliton explosions. The dispersion is adjusted to yield solitary explosions.

The results of this study can be found in:

Steven T. Cundiff, J. M. Soto-Crespo and N. Akhmediev, Experimental Evidence for Soliton Explosions, Phys. Rev. Lett., 88, 073903 (2002).

Polarization Instability of Kerr Spatial Vector Solitons

Spatial vector solitons in an AlGaAs slab waveguide are subject to a polarization instability. At power levels where the nonlinear index change becomes comparable to the birefringence, the fast soliton becomes unstable. The instability is related to coupling of the fast soliton to the slow radiation modes through phase matching. The combined effects of bifurcation and radiation coupling are the processes ultimately limiting the stability of any single-polarization (fast and slow) Kerr soliton. The plot shows the amount of power contained in the main beam.

The results of this study can be found in:

R. R. Malendevich, L. Friedrich and G. I. Stegeman, J. M. Soto-Crespo, N. N. Akhmediev, J. S. Aitchison, Radiation Related Polarization Instability of Kerr Spatial Vector Solitons, Journal of the Optical Society of America B, 19, No 4, pp. 695 - 702 (2002).

Short optical pulses in a nonlinear directional coupler that possesses significant intermodal dispersion are solitons. The intermodal dispersion has only a small effect on the shape of the soliton states, in spite of the fact that it can distort and break up low-energy pulses launched into one arm of the coupler. The intermodal dispersion, however, can cause a drift in the velocity of the soliton pulses.

The results of this study can be found in:

V. Rastogi, K. S. Chiang and N. N. Akhmediev, " Soliton states in a nonlinear directional coupler with intermodal dispersion", Phys. Lett. A 301, 27-34 (2002).

Three stable pulses of different shapes can exist in systems described by the complex Ginzburg±Landau equation, such as passively mode-locked lasers with a fast saturable absorber. At the same cavity parameter values, however, only two of them can coexist, which two depending on the particular values of the parameters. The region of existence for each pulse is investigated numerically. The interaction between each pair of pulses is studied numerically. Using the interaction plane technique, we have found stable bound states of composite pulses.

N. Akhmediev, A. S. Rodrigues, and G. Town, Interaction of dual-frequency pulses in passively mode-locked lasers, Optics Communications, 187, No 2, 419 - 426 (2001).