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Water dam breaking (or dam failure) triggered by the nature disasters such as earthquakes or heavy rainfall can cause huge damage in terms of human lives and properties. Not only for realizing its formation process to evaluate the potential consequences, but also because of the intrinsic rich mathematical and numerical interest, this classical problem has attracted a lot of attention [1-3]. However, clear and accurate experimental investigations are still lacking. In this communication, based on our previous observation of dispersive shock waves (DSW) [4], we revisited the classical dam-breaking problem in nonlinear fiber optics. We studied the propagation of a short optical pulse with an intensity-jump in a dispersion compensating fiber (DCF) that mimics water height jump in hydrodynamics. A sketch of the experimental setup is shown in Fig. 1 (a). We used an electro-optical modulator to generate a step like pulse of 1 ns duration with a background level equals to 15% of the powerful part of the pulse (Fig. 1 (c)). It is then amplified in an erbium doped fiber amplifier to reach 0.6 W peak power and launched inside a DCF whose parameters are listed in Fig. 1's caption. Linear losses of the fiber are almost totally compensated by launching a counter-propagating Raman pump at 1480 nm. The intensity profile at the output of this lossless DCF has been recorded by using an optical sampling oscilloscope, as shown in Fig.1 (e). We clearly see that the optical dam decays into a pair of oppositely propagating DSW (on the left) and rarefaction wave (RW, on the right), separated by a short plateau between them.

A Finite Difference Time Domain approach is used to design and optimize QWIPs optoelectronic devices. Results showing the influence of some parameters on the performance of these devices are presented and discussed.

Optical spatial solitons are known to be unconditionally stable in non local media. We considered their features, even beyond paraxial regime; thus unveiling the existence of ultra-thin self-trapped beam in soft materials. Soft matter is also characterized by disorder. We studied the effect of spatial inhomogeneity in the propagation of multiple filaments generated by non local modulational instability. The disorder was modeled through a stochastic non local nonlinear Schroumldinger equation. It turns out that the number and the distribution of generated light filaments in 2+1D is strongly affected by the fractal dimension D, and a statistical description can be developed by introducing the light structure factor Slight(q) of a "filamented" beam.

This paper reports on recent studies suggesting that optical shocks can rule the dynamics of cw (or quasi-cw) optical field propagating in glass when common phenomena such as four-wave mixing in fibers or catastrophic self-focusing in bulk are considered. The post-shock oscillations evolve into colliding dark solitons that determine the output pattern in a non-recurrent fashion. This scenario based on the defocusing nonlinear Schrodinger equation and its reduction to a hydrodynamical model is substantially confirmed by our experimental data consisting of recorded output spectra and temporal patterns retrieved from SHG-FROG traces. Numerical results also indicate that, during self-focusing, the carrier undergoes steepening until an optical shock form that grows with ellipsoidal shape while dissipating energy

This study presents the search for wave-packets that are both stationary (i.e. invariant during propagation) and localized (i.e. exhibiting a central peak of very small size and duration), in the presence of material dispersion. The new regime that has been investigated, in which the three factors (namely: material chromatic dispersion, X-shape, and nonlinearity) play together their role in affecting the total phase shift, leads to a perfect balance in the ideal case. The process is predicted to occur in quite common operating conditions, namely with focusing Kerr or X/sup (2)/ nonlinearity and normal group velocity dispersion.

The purpose of this work is to show how the evolution of the input wave-envelope profile in phase matched second-harmonic generation is able to force a pure spatial or a pure temporal break-up, depending on the relative weight of diffraction versus group velocity dispersion. In order to clarify the underlying dynamics this study presents the results of 2+1 D numerical simulations (1 spatial, 1 temporal + 1 propagation dimensions). The plots give the spatio-temporal intensity map of the fundamental-wave, at different propagation lengths inside the crystal.

This study presents a detailed analysis based on numerical experiments devoted to the characterization of the non-linear spatio-temporal dynamics of an initially separable (gaussian-like, spherical, short and focused) wave-packet, encompassing second-harmonic generation (SHG) in a conventional, bulk, X/sup (2)/ material. The initial self focusing of the fundamental wave is supported by the chosen positive phase mismatch. As to the temporal broadening, the authors addressed both the case of dominant group-velocity mismatch and the case dominated by positive group-velocity dispersion.

Summary The effect of stimulated Raman scattering on the propagation of ultrashort optical pulses in silica fibers has been recently studied by means of the Schriidinger equation with a delayed contribution to the nonlinearity.1 In this work we extend the analysis to deal with pulses of arbitrary polarization which propagate in the two orthogonal polarization modes of a birefringent fiber. This has important implications for femtosecond pulse compression experiments, where intensity-dependent polarization rotation may be used to eliminate the wings of a compressed pulse, and for all-optical switching devices employing the two polarization modes of a fiber.293 Figure 1 shows examples of computed pulse envelopes emerging from the slow (1 a) and the fast (lb) axis of a birefringent fiber of length z = 0.25 (in soliton units1**), respectively, whenever the input pulse is slightly misaligned with the slow axis. As can be seen, considerable polarization rotation occurs near the edges of the weak pulse component. Moreover, a temporal asymmetry is introduced by the nonistantaneous Raman contribution, in close agreement with recent pulse shaping measurements.4 A similar asymmetry also results in the spectral distributions. By simulating the passage of these pulses through a grating with anomalous dispersion, we have studied the effect of Raman-induced asymmetries on the choice of parameters for optimal pulse compression. Figure 2 illustrates the coupling between linear polarization modes which is predicted to occur in the anomalous dispersion regime for femtosecond solitons in a periodically twisted fiber filter.* The distance is given in terms of the linear coupling length of the polarization coupler. The input pulse is launched on the fast axis (fig. 2(a)): as can be seen, the pulse slowing down due to soliton self-frequency shift competes with the differential group delay and the linear coupling between the modes. The results of the calculations permit an optimal design of femtosecond soliton switching and wavelength demultiplexing experiments with birefringent fibers and filters, in the presence of selfstimulated Raman scattering.