Anisotropic Kerr Nonlinearity Research Articles

Polarization rotation and singularity evolution of fundamental Poincaré beams through anisotropic Kerr nonlinearities

We report a theoretical investigation on polarization rotation and singularity evolution of focused fundamental Poincaré beams in free-space propagation and through isotropic and anisotropic Kerr nonlinear media. It is found that the optical nonlinearity enhances the polarization rotation of the focused beams during propagation. Furthermore, the anisotropy of optical nonlinearity causes the symmetry breaking of the polarization distribution. Further studies show that the C-point and L-line singularities of the lemon Poincaré beams do not change while propagating in free space or through the isotropic nonlinear Kerr medium. Interestingly, the anisotropic Kerr nonlinearity evokes the C-point singularity splitting, and the distortion and birth of L-line singularities. However, the total singularity index always remains the conservation within the light field, regardless of the optical nonlinearity.

Anisotropic nonlinear Kerr media: Z-scan characterization and interaction with hybridly polarized beams.

The interaction of intense laser with matter gives rise to a variety of novel nonlinear optical effects, reflects the nonlinear optical property of a material, and modulates the light propagation behavior. Herein, we investigate anisotropic Kerr nonlinearities induced by both scalar and vectorial optical fields. Firstly, we present the anisotropic third-order nonlinear refraction indexes related to left-hand and right-hand components, which depend on the ellipticity, the dichroism coefficient, the anisotropy coefficient, as well as the crystal orientation angle. Secondly, we develop the elliptically polarized light Z-scan technique for characterizing third-order nonlinear susceptibility tensor in anisotropic nonlinear Kerr media, which is demonstrated experimentally. Lastly, with the known nonlinear optical parameters, we numerically study both the vectorial self-diffraction behaviors and spin angular momentum (SAM) characteristics of hybridly polarized beams induced by an anisotropic Kerr nonlinearity. It is shown that the anisotropic Kerr nonlinearity offers a new approach to manipulate the polarization-structured light field, which has potential applications in SAM manipulation, three-dimensional crystal orientation, and polarization-sensitive detection and sensing.

Varying polarization and spin angular momentum flux of radially polarized beams by anisotropic Kerr media.

Light fields with structured polarization distribution interacting with structured media will result in many novel optical effects in both the linear and nonlinear regimes. In this work, we report a theoretical investigation of both vectorial self-diffraction behaviors and polarization evolution characteristics of a radially polarized beam induced by anisotropic Kerr nonlinearity. By taking the polarization-orientation dependence of the third-order refractive nonlinearity, we study the far-field vectorial self-diffraction patterns of the radially polarized beam using the vectorial Rayleigh-Sommerfeld formulas. Numerical results reveal that the self-diffraction patterns with a four-fold rotational symmetry exhibit hybrid states of polarization. Moreover, the interaction of radially polarized beams with the anisotropic nonlinear Kerr media leads to the redistribution of the spin angular momentum (SAM) flux in the far-field plane. The presented work opens up new avenues for varying polarization and SAM through anisotropic optical nonlinearity.

Dipole solitons in nonlocal nonlinear media with anisotropy

We investigate the existence and stability of dipole-mode solitons in two-dimensional models of nonlocal media with anisotropic Kerr nonlinearity analytically and numerically. We obtain the approximate solution of such elliptic dipole solitons by using the variational approximation. The dynamics of such dipole-mode solitons is governed by the eccentricity of both the input beam and the nonlocal response function. We also compute the stability of the solitons by direct numerical simulations. The effects of the anisotropy of the nonlocal response function on the propagation of the dipole beam are also discussed in detail.

Polarization Rotation in Silicon Waveguides: Analytical Modeling and Applications

The efficient use of optical nonlinearities in silicon is crucial for the implementation of silicon-based photonic devises. In this paper, we present an approximate analytical study of nonlinear polarization rotation in silicon-on-insulator (SOI) waveguides; the rotation is predominantly caused by the effects of self-phase modulation and cross-phase modulation, stemming from the anisotropic Kerr nonlinearity. In the first part of the paper, we analyze the transmittance of the Kerr shutter in the continuous-wave regime and address the problem of its optimization. It is essential for the generality of our conclusions that both free-carrier effects and two-photon absorption are properly accounted for in this study. We specifically show that the signal transmittance may be optimized by adjusting the waveguide length, the pump power, and the incident linear polarizations of pump and signal beams. In the second part of the paper, we examine the problem of power equalization with SOI waveguides. We validate the derived analytical solutions by comparing their predictions with the data from numerical simulations and illustrate the solutions by the examples of practical interest. The results of our work may prove useful for the design and optimization of SOI-based Kerr shutters, all-optical switches, and power equalizers.

Elliptic incoherent solitons in strongly nonlocal media with anisotropic Kerr nonlinearity

The propagation of elliptic incoherent beam in strongly nonlocal media with noninstantaneous anisotropic Kerr nonlinearity is systematically investigated. Using the mutual coherence function approach, we obtain the existence curve of such solitons and an interesting outcome: correlation characteristics of the elliptic incoherent solitons can be anisotropic as well as isotropic. When the existence conditions of solitons are not satisfied, the elliptic incoherent beam will undergo periodic oscillation. Nonstationary evolution behaviors of the elliptic beam are shown in detail by numerical calculation. It is also obtained that the oscillation periods of the beam in x and y direction are different and the elliptic beam will become circular at some propagation distance under special conditions.

Theory of mixed-polarization propagation in anisotropic cubic media

Polarization dynamics are considered in the presence of an anisotropic Kerr non-linearity in the most common semiconductor waveguide geometry. The equations of motion are formulated in terms of Stokes polarization parameters and their Hamiltonian form is derived. Stationary solutions and their stability are found for plane-wave propagation. It is found that the non-integrable problem of mixed-polarization spatial soliton dynamics can be largely explained in terms of the equivalent plane-wave solutions.

Polarisation interactions in birefringent fibre waveguides with anisotropic Kerr nonlinearity

The influence of the antisymmetric components of the fourth-rank nonlinear susceptibility tensor is taken into account in considering the polarisation self-interaction of waves in birefringent fibre lightguides. The effects discussed include the appearance of an instability of a linearly polarised mode with a lower propagation velocity, formation of a nonlinear mode with elliptic polarisation, and self-rotation of the plane of polarisation of linearly polarised light.

Nonlinear-optical activity owing to anisotropy of ultrafast nonlinear refraction in cubic materials

The evolution of the polarization state in a cubic material with an anisotropic Kerr nonlinearity is examined. It is shown that in certain cases this provides a mechanism for nonlinear-optical activity, leaving the state of the polarization unchanged but causing a signif icant rotation in its major axis. The use of the anisotropic ultrafast nonlinear refraction that exists just beneath the half-gap in semiconductors to demonstrate these effects is discussed.