We study large-amplitude one-dimensional solitary waves in photonic crystals featuring competition between linear and nonlinear lattices, with minima of the linear potential coinciding with maxima of the nonlinear pseudopotential, and vice versa (inverted nonlinear photonic crystals, INPCs), in the case of the saturable self-focusing nonlinearity. Such crystals were recently fabricated using a mixture of SU-8 and Rhodamine-B optical materials. By means of numerical methods and analytical approximations, we find that large-amplitude solitons are broad sharply localized stable pulses (quasicompactons, QCs). With the increase of the total power, P , the QC's centroid performs multiple switchings between minima and maxima of the linear potential. Unlike cubic INPCs, the large-amplitude solitons are mobile in the medium with the saturable nonlinearity. The threshold value of the kick necessary to set the soliton in motion is found as a function of P . Collisions between moving QCs are considered too.
We study the influences to the discrete soliton (DS) by introducing linearly long-range nonlocal interactions, which give rise to the off-diagonal elements of the linearly coupled matrix in the discrete nonlinear schrodinger equation to be filled by non-zero terms. Theoretical analysis and numerical simulations find that the DS under this circumstance can exhibit strong digital effects: the fundamental DS is a narrow one, which occupies nearly only one waveguide, the dipole and double-monopole solitons, which occupy two waveguides, can be found in self-focusing and -defocusing nonlinearities, respectively. Stable flat-top solitons and their stagger counterparts, which occupy a controllable number of waveguides, can also be obtained through this system. Such digital properties may give rise to additional data processing applications and have potential in fabricating digital optical devices in all-optical networks.
We introduce a model of resonant optical systems: a waveguide array doped periodically with resonant four-level N-type atoms. The dopant atoms are driven by external fields which induce the effect of the electromagnetically induced transparency (EIT). In this resonant waveguide arrays (RWA) system, the optical field propagates as quasi-discrete diffraction, breathing beam or stable spatial soliton when different initial amplitude and width of the probe are given. The critical values representing these transformations are obtained by the numerical simulations. In a further study of the oblique incidence, the soliton loses a portion of its energy while a kick (i.e., a transverse wave vector) is initially introduced. As the value of the kick becomes larger than a critical value, the soliton collapses.
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