共查询到20条相似文献,搜索用时 31 毫秒
1.
A circular optical fiber consisting of an inhomogeneous nonlinear core bounded by a linear cladding medium is considered here. In this case, the calculation of the nonlinear modes is of practical importance because of the joint effects of nonlinearity and inhomogeneity on the field concentration and the achievable optical confinement. Numerical results indicate that the combination of this type of inhomogeneity along with the characteristics of nonlinearity may play a significant role towards the optical confinement in the core. 相似文献
2.
Journal of Statistical Physics - In this work we prove the nonlinear instability of inhomogeneous steady states solutions to the Hamiltonian mean field (HMF) model. We first study the linear... 相似文献
3.
Bin Chen Kang-Xian Guo Rui-Zhen Wang Zhi-Hai Zhang Zuo-Lian Liu 《Solid State Communications》2009,149(7-8):310-314
The linear and the third-order nonlinear optical absorptions in the asymmetric double triangular quantum wells (DTQWs) are investigated theoretically. The dependence of the optical absorption on the right-well width of the DTQWs is studied, and the influence of the applied electric field on the optical absorption is also taken into account. The analytical expressions of the linear and the nonlinear optical absorption coefficients are obtained by using the compact density-matrix approach and the iterative method. The numerical calculations are presented for the typical GaAs/AlxGa1?xAs asymmetric DTQWs. The results show that the linear as well as the nonlinear optical absorption coefficients are not a monotonous function of the right-well width, but have complex relationships with it. Moreover, the calculated results also reveal that applying an electric field to the DTQWs with a thinner right-well can enhance the linear optical absorption but has no prominent influence on the nonlinear optical absorption. In addition, the total optical absorption is strongly dependent on the incident optical intensity. 相似文献
4.
A. G. Litvak V. A. Mironov S. A. Skobelev L. A. Smirnov 《Journal of Experimental and Theoretical Physics》2018,126(1):21-34
Based on a discrete nonlinear Schrödinger equation (DNSE), we studied analytically and numerically the peculiarities of the self-action of one-dimensional quasi-optic wave beams injected into a spatially inhomogeneous medium consisting of a set of equidistant mutually coupled optical fibers. A variational approach allowing the prediction of the global evolution of localized fields with the initially plane phase front was developed. The self-consistent equations are obtained for the main parameters of such beams (the position of the center of mass, the effective width, and linear and quadratic phase-front corrections) in the aberrationless approximation. The case of radiation incident on a periodic system of nonlinear optical fibers at an angle to the axis oriented along them is analyzed in detail. It is shown that for the radiation power exceeding a critical value, the self-focusing of the wave field is observed, which is accompanied by the shift of the intensity maximum followed by the concentration of the main part of radiation only in one of the structural elements of the array under study. In this case, the beams propagate along paths considerably different from linear and the direction of their propagation changes compared to the initial direction. Asymptotic expressions are found that allow us to estimate the self-focusing length and to determine quite accurately the final position of a point with the maximum field amplitude after radiation trapping a channel. The results of the qualitative study of the possible self-channeling regimes for wave beams in a system of weakly coupled optical fibers in the aberrationless approximation are compared with the results of direct numerical simulations within the DNSE framework. 相似文献
5.
线性聚焦和线性散焦效应对空间光孤子间相互作用的影响 总被引:2,自引:2,他引:0
考虑非均匀一维自聚焦介质的横向不均匀性,利用非线性薛定谔方程满足的守恒律给出了相邻空间孤子间隔的解析式,并对空间孤子之间的相互作用进行了数值模拟.结果表明,线形聚焦效应增强了空间孤子之间的相互作用;而线形散焦效应减弱了空间孤子之间的相互作用.当不考虑介质横向不均匀时,空间孤子之间发生周期性的碰撞.线性散焦效应使相邻空间孤子之间的间隔随传输距离发生周期性的变化,但孤子之间并不发生碰撞.线性聚焦效应使相邻空间孤子随传输距离发生周期性的碰撞,线性聚焦效应具有压制损耗使相邻空间孤子间隔变大的作用. 相似文献
6.
In this work the effects of intense laser on the electron-related nonlinear optical absorption and nonlinear optical rectification in GaAs-Ga1−xAlxAs quantum wells are studied under, applied electric and magnetic field. The electric field is applied along the growth direction of the quantum well whereas the magnetic field has been considered to be in-plane. The calculations were performed within the density matrix formalism with the use of the effective mass and parabolic band approximations. The intense laser effects are included through the Floquet method, by modifying the confining potential associated to the heterostructure. Results are presented for the nonlinear optical absorption, the nonlinear optical rectification and the resonant peak of these two optical processes. Several configurations of the dimensions of the quantum well, the applied electric and magnetic fields, and the incident intense laser radiation have been considered. The outcome of the calculation suggests that the nonlinear optical absorption and optical rectification are non-monotonic functions of the dimensions of the heterostructure and of the external perturbations considered in this work. 相似文献
7.
本文研究了在外电场下高分子的线性极化率和三阶非线性极化率,发现电子电子相互作用使激子线性极化率和三阶非线性极化率都降低,而长程电子关联效应的作用更进一步降低 和。准确地计算高分子聚合物的极化率可以更好的理解共轭聚合物的长程电子关联对有机分子线性和非线性响应的影响,确定其结构与非线性光学性质的关系。 相似文献
8.
本文研究了在外电场下高分子的线性极化率和三阶非线性极化率,发现电子-电子相互作用使激子线性极化率χ(1)xx和三阶非线性极化率χ(3)xxxx都降低,而长程电子关联效应的作用更进一步降低χ(1)xx和χ(3)xxxx.准确地计算高分子聚合物的极化率可以更好的理解共轭聚合物的长程电子关联对有机分子线性和非线性响应的影响,确定其结构与非线性光学性质的关系. 相似文献
9.
R. Khordad G. Rezaei B. Vaseghi F. Taghizadeh H. Azadi Kenary 《Optical and Quantum Electronics》2011,42(9-10):587-600
In this paper, the effect of hydrostatic pressure on both the intersubband optical absorption coefficients and the refractive index changes is studied for typical GaAs/Al x Ga1?x As cubic quantum dot. We use analytical expressions for the linear and third-order nonlinear intersubband absorption coefficients and refractive index changes obtained by the compact-density matrix formalism. The linear, third-order nonlinear, and total intersubband absorption coefficients and refractive index changes are calculated at different pressures as a function of the photon energy with known values of box length (L), the incident optical intensity (I), and Al concentration (x). According to the results obtained from the present work, we have found that the pressure plays an important role in the intersubband optical absorption coefficient and refractive index changes in a cubic quantum dot. 相似文献
10.
In this work we investigate the linear and nonlinear coupling properties of a novel multicore circular dielectric waveguide. The proposed device consists of a circular central core and many circular sectoral cores at the periphery, while the whole structure can be considered as a nonlinear multicore composite optical coupler. Hybrid guided modes in a circular sectoral dielectric waveguide are derived using circular harmonic expansion for the electromagnetic fields and the Point Matching Method (PMM) for the application of boundary conditions. Several cases are investigated varying some of the parameters of the geometry and the optical frequency in order to produce dispersion diagrams. In advance, the electric and magnetic field distributions for the fundamental guided modes are produced, while linear and nonlinear coupling coefficients as well as the sectoral waveguide mode effective area are derived. 相似文献
11.
Filippus S. Roux 《Optics Communications》2012,285(6):947-952
The statistical distributions of optical vortices or topological charge in stochastic optical fields can be inhomogeneous in both transverse directions. Such two-dimensional inhomogeneous vortex or topological charge distributions evolve in a complex way during free-space propagation. While the evolution of one-dimensional topological charge densities can be described by a linear diffusion process, the evolution of two-dimensional topological charge densities exhibits some additional nonlinear dynamics. Here we propose a phase drift mechanism as a partial explanation for this additional nonlinear dynamics. Numerical results are presented in support of this proposal. 相似文献
12.
M.E. Mora-Ramos C.A. Duque E. Kasapoglu H. Sari I. Sökmen 《Journal of luminescence》2012,132(4):901-913
In this work we are studying the intense laser effects on the electron-related linear and nonlinear optical properties in GaAs–Ga1?xAlxAs quantum wells under applied electric and magnetic fields. The calculated quantities include linear optical absorption coefficient and relative change of the refractive index, as well as their corresponding third-order nonlinear corrections. The nonlinear optical rectification and the second and third harmonic generation coefficients are also reported. The DC applied electric field is oriented along the hererostructure growth direction whereas the magnetic field is taken in-plane. The calculations make use of the density matrix formalism to express the different orders of the dielectric susceptibility. Additionally, the model includes the effective mass and parabolic band approximations. The intense laser effects upon the system enter through the Floquet method that modifies the confinement potential associated to the heterostructure. The results correspond to several configurations of the dimensions of the quantum well, the applied electric and magnetic fields, and the incident intense laser radiation. They suggest that the nonlinear optical absorption and optical rectification are nonmonotone functions of the dimensions of the heterostructure and of the external perturbations considered in this work. 相似文献
13.
A. -B.M.A. Ibrahim J. Osman 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,63(2):193-198
In this paper we investigate the intrinsic optical bistability (IOB) in a
ferroelectric (FE) single layer using an alternative analysis. The FE
material is considered to have an intensity-dependent refractive index where
the third order nonlinear susceptibility χ(3) acts like Kerr
coefficient. The nonlinear response of the FE medium is modeled using the
Landau-Khalatnikov (LK) dynamical equation with the nonlinear anharmonic
potential obtained from the Landau-Devonshire free energy expressed in terms
of polarization. Within a single frequency approximation, the
electromagnetic wave equation is written in terms of the polarization P
rather than the electric field E as the dependent variable. With the
application of the nonlinear boundary conditions we have derived expressions
for both reflectance and transmittance as a function of the electric field
incident amplitude, polarization and other material parameters. The
formalism proves to be more suitable for FE materials since most of these
materials have highly linear and nonlinear coefficients especially when the
operating frequency is in the resonance region. The effects of thickness,
operating frequency and temperature on BaTiO3 single film are
investigated theoretically. The results presented here agree in principle
with the recent experimental observations of intrinsic OB in BaTiO3
monocrystal and other FE photorefractive materials. 相似文献
14.
XUE Yu-Shan TIAN Bo ZHANG Hai-Qiang LIU Wen-Jun LI Li-Li QI Feng-Hua ZHAN Yan 《理论物理通讯》2009,52(5):888-896
With the aid of computation, we consider the variable-coefficient coupled nonlinear Schrödinger equations with the effects of group-velocity dispersion, self-phase modulation and cross-phase modulation, which have potential applications in the long-distance communication of two-pulse propagation in inhomogeneous optical fibers. Based on the obtained nonisospectral linear eigenvalue problems (i.e. Lax pair), we construct the Darboux transformation for such a model to derive the optical soliton solutions. In addition, through the one- and two-soliton-like solutions, we graphically discuss the features ofpicosecond solitons in inhomogeneous optical fibers. 相似文献
15.
J.L. Paz A. Mendoza-García A. Mastrodoménico 《Journal of Quantitative Spectroscopy & Radiative Transfer》2011,112(1):100-108
In this study, we determined the absorptive and dispersive optical profiles of a molecular system coupled with a thermal bath. Solvent effects were explicitly considered by modelling the non-radiative interaction with the solute as a random variable. The optical stochastical Bloch equations (OSBE) were solved using a time-ordered cumulant expansion with white noise as a correlation function. We found a solution for the Fourier component of coherence at the third order of perturbation for the nonlinear Four-wave mixing signal and produced analytical expressions for the optical responses of the system. Finally, we examined the behaviour of these properties with respect to the noise parameter, frequency detuning of the dynamic perturbation, and relaxation times. 相似文献
16.
In this paper, we consider the process of optical recording and decay of transient spatial structures in a system with a nonlinear response caused by incoherent saturation of three-level centers. The main attention is devoted to the thermal mechanism of phase recording in media with a temperature-independent heat conductivity. The relaxation of an inhomogeneous temperature field and the diffraction of a probe beam from the transient structure are studied. The designed theoretical model satisfactorily describes the obtained experimental results and allows the evolution of a temperature field to be viewed. 相似文献
17.
S. E. Savotchenko 《Journal of Experimental and Theoretical Physics》2018,127(3):437-447
Spatially periodic inhomogeneous stationary states are shown to exist near a thin defect layer with nonlinear properties separating nonlinear Kerr-type crystals. The contacts of nonlinear self-focusing and defocusing crystals have been analyzed. The spatial field distribution obeys a time-independent nonlinear Schrödinger equation with a nonlinear (relative to the field) potential modeling the thin defect layer with nonlinear properties. Both symmetric and asymmetric states relative to the defect plane are shown to exist. It has been established that new states emerge in a self-focusing crystal, whose existence is attributable to the defect nonlinearity and which do not emerge in the case of a linear defect. The dispersion relations defining the energy of spatially periodic inhomogeneous stationary states have been derived. The expressions for the energies of such states have been derived in an explicit analytical form in special cases. The conditions for the existence of periodic states and their localization, depending on the defect and medium characteristics, have been determined. 相似文献
18.
In this paper, we have studied optical properties of spherical quantum dots by using Rosen-Morse potential. In this regard, we have first solved the Schrodinger equation and obtained energy levels and wave functions by applying Nikiforov-Uvarov (NU) method. Then, by using density matrix method, we have applied analytical expressions for the linear and third-order nonlinear absorption coefficient and refractive index changes. The results show that the total refractive index changes and the absorption coefficients increase and shift towards higher by enhancing height potential. 相似文献
19.
In this work, the linear and nonlinear optical properties are studied theoretically in asymmetric (CdS/ZnSe/BeTe)/(ZnSe/BeTe) quantum wells. The electronic states are calculated using the envelope wave function approximation and the intersubband transition energies are studied as a function of CdS and ZnSe well thicknesses as well as doping concentration. The optimum parameters carrying out the transition energy 0.8 eV (1.55 μm wavelength) are given. Results are presented for the linear, the third order nonlinear optical absorption and the refractive index changes in the studied heterostructure. Results show that the changes in the linear and the third order nonlinear optical absorption as well as refractive index change are as important as the temperature is high, the nonlinear terms must be taken into consideration especially near the resonance. 相似文献
20.
In this paper, the effects of hydrostatic pressure, temperature and intense laser field on the linear and nonlinear optical processes in the conduction band of a square quantum well are numerically investigated in the effective mass approximation. The analytical expressions of optical properties are obtained by using the compact density-matrix approach. The numerical results are presented for typical square GaAs/AlxGa1?xAs single quantum well system. The nonlinear optical absorption and refractive index changes depending on the hydrostatic pressure and intense laser field are investigated for two different temperature values. The results show that the intense laser field, the hydrostatic pressure and the temperature have a significant effect on the optical characteristics of these structures. 相似文献