Nonlinear Dielectric Media Research Articles

Nonlinearized nonlinear electromagnetic guided waves in a circle cylindrical waveguide filled with nonlinear dielectric medium

We consider a problem of propagation of monochromatic electromagnetic waves in a circle cylindrical waveguide filled with nonlinear dielectric medium. The permittivity of the waveguide is described by the Kerr law, which is one of the most important nonlinear dependence in nonlinear optics. In order to find guided waves we develop an original mathematical approach that allows us to prove existence of infinitely many guided waves. In addition, we prove that only a finite number of the founded nonlinear guided waves have linear counterparts; the others are nonlinearizable solutions. Numerical results are also presented.

Photon propagation in a material medium on a curved spacetime

We consider a nonlinear dielectric medium surrounding a static, charged and spherically symmetric compact body which gravitational field is driven by general relativity. Considering the propagating waves on the dielectric medium, we describe the trajectory of light as geodesics on an effective geometry given by Hadamard’s discontinuities. We analyze some consequences of the effective geometry in the propagation of light, with relation to the predictions of the background gravitational field, that includes corrections on the geometrical redshift and on the gravitational deflection of light. We show that the background electromagnetic field polarize the material medium, such that different polarizations of light are distinguished by different corrections on these quantities. As a consequence, we have two possible paths for the trajectory of light in such configuration, that coincide if we turn off the electromagnetic field or if the permittivity is constant. We show that the effective metric associated to the negative polarization, for a given dependence of the dielectric permittivity, is conformally flat.

Spontaneous fractional Chern insulators in transition metal dichalcogenide moiré superlattices

Moir{\'e} superlattice realized in two-dimensional heterostructures offers an exciting platform to access strongly-correlated electronic states. In this work, we study transition metal dichalcogenides (TMD) Moir{\'e} superlattices with time-reversal-symmetry and nontrivial spin{/valley}-Chern numbers. Utilizing realistic material parameters and the method of exact diagonalization, we find that at a certain twisting angle and fractional filling, gapped fractional topological states, i.e., fractional Chern insulators, are naturally {stabilized} by simply introducing the Coulomb repulsion. In contrast to fractional quantum Hall systems, where the time-reversal symmetry has to be broken explicitly, these fractional states break the time-reversal symmetry spontaneously. {We show that the Chern number contrasting in the opposite valleys imposes a strong constraint on the nature of fractional Chern insulator and the associated low energy excitations.} We also propose to realize the non-abelian Moore-Read state in TMD Moir{\'e} superlattice sandwiched between nonlinear dielectric media.

Quantization and soliton-like solutions for the Phi Psi -model in an optic fiber

In the framework of a mesoscopical model for dielectric media we provide an analytical description for the electromagnetic field confined in a cylindrical cavity containing a finite dielectric sample. This system is apted to simulate the electromagnetic field in a optic fiber, in which two different regions, a vacuum region and a dielectric one, appear. A complete description for the scattering basis is introduced, together with field quantization and the two-point function. Furthermore, we also determine soliton-like solutions in the dielectric, propagating in the sample of nonlinear dielectric medium.

Light propagation along a helical waveguide: variational approach

We investigate numerically and analytically light propagation in a single spiral waveguide formed in a nonlinear dielectric medium, in the regime of low spatial frequency of the waveguide rotation. We present a general variational approach for computing soliton parameters analytically, which includes various types of nonlinearity. In the particular case of media with cubic-quintic nonlinearity, analytical expressions found are in very good agreement with the numerical findings.

High frequency gravitational waves generation by optical methods

In this paper, various types of sources of gravitational waves are considered. The use of the effect of mutual conversion of electromagnetic and gravitational waves in a nonlinear optical dielectric medium is proposed as a promising method for creating a source of gravitational-wave radiation.

Electromagnetic and gravitational waves conversion in a nonlinear dielectric medium by intense light source irradiation

Various types of gravity wave sources were considered in this paper. It is proposed to use the effect of mutual conversion of electromagnetic and gravitational waves in a nonlinear optical dielectric medium irradiated by an intensive light source as a perspective method of generating gravitational-wave radiation.

Rotating solitons supported by a spiral waveguide

We investigate numerically light propagation in a single spiral waveguide formed in a nonlinear dielectric medium for a low spatial frequency of the waveguide rotation. We present a general procedure for finding solitonic solutions in spiral waveguiding structures, as well as the variational approach to calculate soliton parameters analytically. Solitons supported by the spiral waveguide perform robust stable rotational oscillatory motion, with the period predicted by their static characteristics, without any signatures of wave radiation or soliton decay over many rotation periods and diffraction lengths.

Propagation of surface plasmon polaritons in monolayer graphene surrounded by nonlinear dielectric media

The propagation of s-polarized surface plasmon polaritons (SPPs) was investigated in a monolayer graphene sheet surrounded by two dielectric media on each side, so that one or both sides of the media were linear or nonlinear with Kerr-type nonlinearity. The plasmonic properties including the wave propagation index neff, the penetration depth, the time-averaged power flow and the spatial profile of electric and magnetic fields were calculated for the following structures: Linear medium/Graphene/Linear medium (L/G/L), Nonlinear medium/G/L (NL/G/L) and NL/G/NL. The analysis of the nonlinear coefficient effect on the SPP properties showed that increasing the nonlinearity in NL/G/L enhanced neff. However, for a smaller difference between the nonlinearity of layers, neff decreased in NL/G/NL. By comparing between the proposed structures, it was found that while large values of neff can be obtained from L/G/L, its frequency confinement is smaller than that of NL/G/L and NL/G/NL. Furthermore, NL/G/L and NL/G/NL were able to support localized nonlinear modes, leading to enhanced frequency confinement of transverse electric (TE) waves in the presence of nonlinearity. Increasing the nonlinearity in NL/G/L confined the spatial profile of the electric field near the graphene interface, indicating the existence of surface plasmon solitons. The influence of the graphene chemical potential μ on the plasmonic properties of the structures was also investigated. In this case, it was found that the plasmonic properties can be controlled by μ. Our calculations may solve the difficulties in TE surface plasmons for application in optics and plasmonics.

Generation and detection of high frequency gravitational waves at intensive electromagnetic excitation

The ways of generating and detecting of high frequency gravitational wave in free space and in nonlinear dielectric media under intensive electromagnetic emission excitation have been analyzed. It was shown that there is the opportunity to realize the parametric process of gravitational wave generation with high frequency ωg = 2ω0 due to combining of two electromagnetic waves with frequency ω0. In the dielectric medium synchronism conditions may be reached if the frequency ω0 of exciting light corresponds to so call unitary polaritons, characterized by unity refraction index. The detection of gravitational waves with frequency ωg = 2ω0 may be examined by means of the third harmonic generation registration in corresponding dielectric media.

Hybrid Organic-Plasmonic Nanoantennas with Enhanced Third-Harmonic Generation.

Resonantly excited plasmonic gold nanoantennas are strong sources of third-harmonic (TH) radiation. It has been shown that the response originates from large microscopic nonlinearity of the gold itself, which is enhanced by the near-field of the plasmonic nanoantenna. To further enhance this response, one can incorporate nonlinear media into the near-fields of the nanoantenna, as an additional TH source. To obtain a significant contribution from the added medium, its nonlinear susceptibility should be comparable to that of the antenna material. Many organic materials offer the necessary nonlinear susceptibility and their incorporation is possible with simple spin-coating. Furthermore, organic materials are often susceptible to photodegradation. This degradation can be used to investigate the influence of organic materials on the hybrid system. Our investigated hybrid organic plasmonic nanoantenna system consists of a gold nanorod array and poly(methyl methacrylate) as the nonlinear dielectric medium. The experiments clearly reveal two contributions to the generated TH radiation, one from the nanoantenna itself and one from the polymer. The nonlinear response of the hybrid material exceeds the response of both individual constituents and opens the path to more efficient nanoscale nonlinear light generation.

Controlled opacity in a class of nonlinear dielectric media

Motivated by new technologies for designing and tailoring metamaterials, we seek properties for certain classes of nonlinear optical materials that allow room for a reversibly controlled opacity-to-transparency phase transition through the application of external electromagnetic fields. We examine some mathematically simple models for the dielectric parameters of the medium and compute the relevant geometric quantities that describe the speed and polarization of light rays.

Controllable chaotic dynamics in a nonlinear fiber ring resonators with balanced gain and loss

We show the possibility of controlling the dynamical behavior of a single fiber ring (SFR) resonator system with the fiber being an amplified (gain) channel and the ring being attenuated (loss) nonlinear dielectric medium. Our model is based on the simple alterations in the parity time symmetric synthetic coupler structures proposed recently [A. Regensburger et al., Nature 488, 167 (2012)]. The system has been modeled using the transfer matrix formalism. We find that this results in a dynamically controllable algorithm for the chaotic dynamics inherent in the system. We have also shown the dependence of the period doubling point on the input amplitude, emphasizing on the dynamical aspects. Moreover, the fact that the resonator essentially plays the role of a damped harmonic oscillator has been elucidated with the non-zero intensity inside the resonator due to constant influx of input light.

Intensity modulated optical transmission in a non-linear dielectric environment with an embedded mono-layer transition metal dichalcogenide

We study the optical behavior of an arrangement in which the interface between a linear and non-linear dielectric media is covered by an embedded mono-layer of transition metal dichalcogenides (TMDC). The optical behavior is qualitatively obtained through transmission and reflection coefficients which are a function of the third order non-linear susceptibility of the Kerr-type dielectric and the inter-band optical conductivity of the TMDC mono-layer. The inter-band optical conductivity of the TMDC mono-layer is calculated using the Kubo formalism from the linear response theory. In particular, we theoretically demonstrate that the optical response of this structure can be switched between the total internal reflection and a normal transmission regime by controlling the intensity of the incident radiation. The reflection and transmission functions are shown to be amenable to further control by altering the inter-band optical conductivity of the embedded TMDC mono-layer. The optical conductivity is directly related to its energy dispersion. We specifically choose two TMDC mono-layers, MoS2 and WSe2, which have nearly identical dispersion parameters apart from a much stronger spin-orbit coupling in the latter. The stronger spin-orbit coupling in WSe2 does not significantly alter the inter-band optical conductivity to manifest as an enhanced reflection spectrum. However, we find that application of an external perturbation such as strain could be effectively used to modulate the overall optical response. We conclude by discussing briefly the phenomenon of optical bistability which arises in materials exhibiting optical non-linearity via an intensity-dependent refractive index.

Derivation of Hawking radiation in dispersive dielectric media

Motivated by recent experimental efforts, we study a black hole analog induced by the propagation of a strong laser pulse in a nonlinear dielectric medium. Based on the Hopfield model (one pair of Sellmeier coefficients), we perform an analytic and fully relativistic microscopic derivation of the analog of Hawking radiation in this setup. The Hawking temperature is determined by the analog of the surface gravity (as expected), but we also find a frequency-dependent gray-body factor (i.e., a nonthermal spectrum at infinity) due to the breaking of conformal invariance in this setup.

Transparency in nonlinear frequency conversion

Suppression of wave scattering and the realization of transparency effects in engineered optical media and surfaces have attracted great attention in the past recent years. In this work the problem of transparency is considered for optical wave propagation in a nonlinear dielectric medium with second-order $\chi^{(2)}$ susceptibility. Because of nonlinear interaction, a reference signal wave at carrier frequency $\omega_1$ can exchange power, thus being amplified or attenuated,when phase matching conditions are satisfied and frequency conversion takes place. Therefore, rather generally the medium is not transparent to the signal wave because of 'scattering' in the frequency domain. Here we show that broadband transparency, corresponding to the full absence of frequency conversion in spite of phase matching, can be observed for the signal wave in the process of sum frequency generation whenever the effective susceptibility $\chi^{(2)}$ along the nonlinear medium is tailored following a suitable spatial apodization profile and the power level of the pump wave is properly tuned. While broadband transparency is observed under such conditions, the nonlinear medium is not invisible owing to an additional effective dispersion for the signal wave introduced by the nonlinear interaction.

The Hopfield model revisited: covariance and quantization

There are several possible applications of quantum electrodynamics in dielectric media which require a quantum description for the electromagnetic field interacting with matter fields. The associated quantum models can refer to macroscopic electromagnetic fields or, alternatively, to mesoscopic fields (polarization fields) describing an effective interaction between electromagnetic field and matter fields. We adopt the latter approach, and focus on the Hopfield model for the electromagnetic field in a dielectric dispersive medium in a framework in which space–time dependent mesoscopic parameters occur, like susceptibility, matter resonance frequency, and also coupling between electromagnetic field and polarization field. Our most direct goal is to describe in a phenomenological way a space–time varying dielectric perturbation induced by means of the Kerr effect in nonlinear dielectric media. This extension of the model is implemented by means of a Lorentz-invariant Lagrangian which, for constant microscopic parameters, and in the rest frame, coincides with the standard one. Moreover, we deduce a covariant scalar product and provide a canonical quantization scheme which takes into account the constraints implicit in the model. Examples of viable applications are indicated.

Kerr effect-assisted self-compression in dielectric to single-cycle pulse width and to terawatt power level in mid-IR

The self-compression of sub-TW mid-IR (λ=4–5µm) femtosecond laser pulse in a non-linear dielectric medium was numerically modeled. Combination of the Kerr non-linearity and negative group velocity dispersion in CaF2 crystal was found to result in compression of the incident laser pulse to a 1–2-cycle pulse width. The possibility for suppression of small-scale self-focusing in conditions when the pulse power was several orders of magnitude above the critical self-focusing power was analyzed. Intrinsic concentration of free carriers was found to play important role in pulse evolution during its propagation.

Evolution of the width of a one-and-a-half-cycle optical pulse in a nonlinear dielectric medium

Simple mathematical expressions are derived to show how the velocity of the center of gravity and the rms width of initially one-and-a-half-cycle pulses depend on the original central frequency and field amplitude, as well as on the properties of nonlinear media with dispersion. It is shown that self-compression of the pulse or its solitonlike (with no change of width) propagation in a medium with positive nonlinearity is not observed even when the central frequency of the pulse lies in the region of anomalous group dispersion of the medium. The central frequency of the pulse, at which its rate of dispersion blurring in the medium is minimal, is computed.

Nonlinear TE-polarized surface polaritons on graphene

We analyze the propagation of electromagnetic waves along the surface of a nonlinear dielectric medium covered by a graphene layer. We reveal that this system can support and stabilize nonlinear transverse electric (TE) plasmon polaritons. We demonstrate that these nonlinear TE modes have a subwavelength localization in the direction perpendicular to the surface, with the intensity much higher than that of an incident wave which excites the polariton.