The intrachannel interaction of pulses in weakly nonlinear coherent optical fiber lines is theoretically investigated. It is shown that the main contribution to the perturbation of the optical field comes from resonant interactions of ordered triplets of pulses. The structure of triplets is determined. The weight contributions of such interactions are calculated. A classification of interactions using Loeschian numbers is proposed. Using computer simulation, the dependence of the average energy of the optical field perturbations on the distance is shown. Based on the performed analysis, an effective algorithm is proposed for assessing the perturbations resulting from intrachannel interaction.

We formulate the inverse scattering transform for the scalar Maxwell-Bloch system of equations describing the resonant interaction of light and active optical media in the case when the light intensity does not vanish at infinity. We show that pure background states in general do not exist with a nonzero background field. We then use the formalism to compute explicitly the soliton solutions of this system. We discuss the initial population of atoms and show that the pure soliton solutions do not correspond to a pure state initially. We obtain a representation for the soliton solutions in determinant form, and explicitly write down the one-soliton solutions. We next derive periodic solutions and rational solutions from the one-soliton solutions. We then analyze the properties of these solutions, including discussion of the sharp-line and small-amplitude limits, and thereafter show that the two limits do not commute. Finally, we investigate the behavior of general solutions, showing that solutions are stable (i.e., the radiative parts of solutions decay) only when initially atoms in the ground state dominant, i.e., initial population inversion is negative.

Current paper represents the results of viscosity and density measurements of vacuum oils for diffusion vacuum pumps. Vacuum oil samples are represented by the following brands: VM-1S, LEYBONOL LVO 500 and Alcarin-D24. All the measurements have been carried out at atmospheric pressure: viscosity has been measured by the capillary method in the temperature range from 293 K to 373 K, and density has been measured by the pycnometer and hydrostatic weighing methods in the temperature range from 293 K to 473 K.

We investigate the polarization switching phenomenon for a one-soliton solution to the \begin{document}$ \Lambda $\end{document} -configuration Maxwell-Bloch equations in the case of initial coherence in the material, corresponding to the forbidden transition between the two lower energy levels. We find two polarization states that are stationary. They are not the purely right- and left-circularly polarized solitons, as in the case of zero initial coherence, but rather two mixed, elliptically polarized, states. These polarization states, of which only one is asymptotically stable, depend on both the initial population levels of the lower states and the coherence value. We also find the existence of superluminal soliton propagation, but through numerical simulations show this solution to be unstable, and therefore likely not realizable physically.

We present exact N-soliton optical pulses riding on a continuous-wave (c.w.) beam that propagate through and interact with a two-level active optical medium. Their representation is derived via an appropriate generalization of the inverse scattering transform for the corresponding Maxwell-Bloch equations. We describe the single-soliton solutions in detail and classify them into several distinct families. In addition to the analogues of traveling-wave soliton pulses that arise in the absence of a c.w. beam, we obtain breather-like structures, periodic pulse-trains and rogue-wave-type (i.e., rational) pulses, whose existence is directly due to the presence of the c.w. beam. These soliton solutions are the analogues for Maxwell-Bloch systems of the four classical solution types of the focusing nonlinear Schrodinger equation with non-zero background, although the physical behavior of the corresponding solutions is quite different.

In this paper possibility of creating a medium based on graphene-dielectric structures with the hyperbolic shape wave number dispersion is considered for the case when two types of graphene sheets with different chemical potentials periodically alternate. Using the Bloch theorem and the transfer matrix method, dispersion relations for the light wave numbers are derived for the layered structure and the possibility is demonstrated to manipulate the light propagation. The optical conductivity of graphene sheets is known to be frequency dependent and in the present scrutiny it is estimated via Kubo formula which simultaneously accounts for both the inter band and the intraband transitions of electrons. To apply the transfer matrix method we routinely express the amplitudes of the incident and reflected radiation at the input to the layered structure in terms of the amplitudes of electromagnetic waves at the output. The transmission spectrum of the layered dielectric medium which is sliced by two types of graphene sheets with different chemical potentials have a staircase behavior. It is demonstrated that the jump points in the transmission spectrum are simply controlled by adjusting the values of chemical potentials of graphene sheets.

We experimentally demonstrate feasibility of simultaneous use of Differential Phase Shift Keying (DPSK) and Amplitude Shift Keying (ASK) formats (orthogonal modulation) using injection-locked semiconductor laser. Experimental study shows significant improvement of the bit-error-rate (BER) and doubling of the system capacity.

Propagation of the surface waves on the interface between an uniaxial hyperbolic material and an isotopical topological insulator is studied. The cases of the anisotropy axes is normal to interface or one is coplanar to interface are discussed. The dispersion relations are derived and analyzed. The conditions of the existence of the surface waves are established.

Cobalt nanoparticles with high quality crystal structure and spin polarization support an excellent plasmon resonance at about 275 nm, which is comparable with gold nanoparticles. The quality of plasmon resonance is highly correlated with the superparamagnetic response of the isolated nanoparticles and disappeared in the aggregates. The fluorescence enhancement of about 3×10 3 for surfactant molecules is demonstrated.

One of the main factors impeding further progress in the field of application of met materials is significant energy losses due to the physical nature of exploited plasmon resonance, and their compensation is the most urgent problem to be addressed by the modern science of met materials. That is why this paper studies the parametric interaction of electromagnetic waves and, in particular, the process of generation and amplification of the second harmonic generation in met materials with the negative refractive index. It is found that the fundamental waves in the process of the second harmonic generation cannot exchange energy through the second harmonic wave at the non-collinear phase matching, and, thus, further consideration is required of optical rectification of the field in the nonlinear met materials.

We consider the coupled forward and backward waves propagating in two dimensional array of waveguide, which are featured by a positive and negative refraction indexes. The existence of the flat band under certain conditions is demonstrated.

This paper discusses the refraction of an ultrashort pulse of an electromagnetic field at a nonlinear interface of dielectric media. The nonlinearity is caused by the presence of a thin film of resonance-absorbing atoms. When local-field effects are negligible, the system of model equations is completely integrable, and this makes it possible to find an exact solution. It is shown that the refracted pulse breaks up into several solitons, whose number depends on the angle of incidence. (C) 2015 Optical Society of America.

Electromagnetic field scattering on a 2D array of rf-SQUIDs is considered. We show that the scattering changes for large amplitudes of the incident electromagnetic wave; above a critical amplitude, two different refraction states occur (bistability). In particular, for these two states, the transmitted wave polarization and angle of refraction are different. One could then switch the direction of propagation of the electromagnetic wave and its polarization with a “thin film”, whose thickness is much smaller than the wavelength.

The parametric interaction of electromagnetic waves in a medium with a negative index of refraction is considered. Two cases of Kerr and quadratic nonlinearities are investigated. The properties of nonlinear coupler, channels of which made of material with opposing signs of refraction index, are studied. Dynamics of extremely short pulses in the homogeneous doubly-resonant medium is analyzed in the framework of Maxwell-Duffing-Lorentz model. The new type of quasi-solitons is presented.

We consider the coupled electromagnetic waves propagating in a nonlinear medium, which is featured by a positive and negative refraction indexes. The backward waves can be propagating in this case. The example of the true soliton is discussed. In general case the coupled forward and backward solitary wave can be found. They are analogues to the optical solitons.

On the basis of the classical Maxwell's equations the corresponding wave equations are derived for description of multiwave interactions in transition metamaterials whose refractive index varies along the sample from positive to negative values. The phenomenon of second harmonic generation is redicted in the transition layer near the point at which the refractive index turns zero, even at low intensities of the fundamental pumping wave. With the help of FDTD (finite difference time domain) mathematical modeling method it is found that the efficiency of the second harmonic generation in transition metamaterials strongly depends on the angle of incidence and the thickness of the transition layer. Specific recommendations are developed for the construction of a compact second harmonic generator based on transition metamaterials.

This work highlights a mechanism for inducing axial anisotropy in side-chain nitroazobenzene (NAB) polymer thin films based on the combined effect of both local dc electrical poling and the longitudinal optical near-field. We show that highly anisotropic NAB chromophores are effectively oriented in the glassy environment under optical pumping with 632.8 nm excitation wavelength, which is out of the absorption band of chromophores. Axial anisotropy across the polymer thin film and its non-centrosymmetric behavior beyond the diffraction limit are experimentally rendered with tip-enhanced Raman scattering microscopy and scanning Kelvin probe microscopy.

We scrutinize the concept of integrable nonlinear communication channels, resurrecting and extending the idea of eigenvalue communications in a novel context of nonsoliton coherent optical communications. Using the integrable nonlinear Schrödinger equation as a channel model, we introduce a new approach-the nonlinear inverse synthesis method-for digital signal processing based on encoding the information directly onto the nonlinear signal spectrum. The latter evolves trivially and linearly along the transmission line, thus, providing an effective eigenvalue division multiplexing with no nonlinear channel cross talk. The general approach is illustrated with a coherent optical orthogonal frequency division multiplexing transmission format. We show how the strategy based upon the inverse scattering transform method can be geared for the creation of new efficient coding and modulation standards for the nonlinear channel.

The coupled electromagnetic waves propagating in a waveguide array, which consists of alternating waveguides of positive and negative refraction indexes, are discussed. The pair of positive-negative waveguides acts as oppositely directional coupler. The stop band in the spectrum of linear waves occurs. When pairs of these waveguides are collected in array or bundle the spectral properties of the resulted device are modified. We study spectral gaps in these waveguide systems and demonstrate that the number of waveguides and helical spatial twist of the array can be used to control the size of the gap.

Second harmonic generation is considered in lossy negative-index metamaterials. It is shown that energy transfer from fundamental to harmonic takes place in the entire sample for the range of phase mismatch values. Note that in conventional case this range collapses to the point (ideal phase matching). The dependance of the boundary of this range as function of dissipation values is obtained using computer simulations.