Optical responses of dilute anisotropic composites：numerical calculations via Green‘s function formalism

We investigate the linear and nonlinear optical responses of dilute anisotropic networks using Green's function formalism [Gu Y et al 1999 Phys. Rev. B 59 12847]. For different applied fields, numerical calculations indicate that a large third-order nonlinear enhancement and a broad infrared absorption arise from the geometric anisotropy. We also show the overlap and separation between the absorption peak and nonlinear enhancement peak when the applied field is parallel and perpendicular to the anisotropy, respectively. The results can be understood in terms of the inverse participation ratios with q=2 and the spectral distribution of optical responses.     

Optical Reskponse of Metal—Dielectric Composite Containing Interfacial Layers

A phenomenological approach nto investigate the effect of interfacial layers on the absorption of metaldielectric composite at elevated temperatures is put forward by making use of a model in which weakly nonlinear spherical metallic particles with linear concentric shells are randomly embedded in a linear host.Corresponding formulae in terms of the interfacial factor are derived in detail by incorporating Taylor expansion and Drude model.We take Ag/MgF2 composite as numerical calculation.It is concluded that such absorption is dependent not only on the temperature,but also on the properties of interfacial layers.Many other interesting phenomena are shown.     

Elastic interaction of point defects with an edge dislocation loop within the Green’s function formalism

The universal expressions have been obtained for components of the tensor Green’s function of an elastically anisotropic hexagonal medium. In contrast to the classical expressions (the Lifshitz–Rosenzweig method), they do not contain uncertainties of the type 0/0 upon the transition to the isotropic approximation and hold true for any hexagonal crystal. As an example of their use, the displacement and strain fields created by an edge dislocation loop lying in the basal plane of the crystal have been calculated.     

Quantum transport of spin-polarized carriers in quasi paramagnetic quantum wires: Green’s function formalism

In this paper, the Schrödinger equation is solved for approximation of the ground state energies and associated wave functions of carriers confined in a rectangular semiconductor (SC) quantum wire embedded in a SiO₂ matrix. The problem was treated with the effective one band Hamiltonian. The finite difference scheme was used for the discretization of 2D Schrödinger equation and LAPACK package to resolve the band matrix. The energy levels were determined and the coupling between quantum wires was investigated. The effect on energies and relative wave functions of quantum wires number, size and separation was studied. The results obtained show that the energy levels can be importantly modified and controlled by these parameters. The interaction is manifested by a reduction in energies and an increase in the peak value of the wave function of the higher energy wire. This study offers a fast and inexpensive way to check device designs and processes and can be used in diverse device applications.     

Preparation and Optical Properties of SnO2／SiO2 Nanocomposite

SnO2/SiO2 nanocomposites have been prepared by the soaking-thermal-decomposing method, tin oxide nanoparticles are uniformly dispersed in the mesopores of silica. The optical absorption edge of the obtained nanocomposite presents a redshift compared with bulk tin oxide, With the increasing annealing temperature during the procedure of the sample preparation, the optical absorption edge of the sample moves to shorter wavelength (blueshift). These optical properties can be ascribed to the amorphous structure and band defects of surface layers of the tin oxide nanoparticles.     

A new approach of solving Green’s function for wave propagation in an inhomogeneous absorbing medium

A new approach is developed to solve the Green's function that satisfies the Hehmholtz equation with complex refractive index. Especially, the Green's function for the Helmholtz equation can be expressed in terms of a one-dimensional integral, which can convert a Helmholtz equation into a Schr?dinger equation with complex potential. And the Schr?dinger equation can be solved by Feynman path integral. The result is in excellent agreement with the previous work.     

The Green’s function method in the problem of sound diffraction by an elastic shell of noncanonical shape

Using the Green function method and dynamic elasticity theory, we obtain a solution to the problem of sound diffraction by elastic shells of noncanonical shapes formed by spheroidal, cylindrical, and spherical bodies. The angular scattering characteristics of such compound bodies with different wave sizes are calculated.     

Enhanced Nonlinear Absorption and Optical Limiting Properties of Organic Material ZnTBP—CA—PhR in a DA—ET System

Nonlinear absorption of the organic material Zn-tetrabenzoporphin-cronicacid-phenonxy resin(ZnTBP-CA-PhR) in the donor-acceptor energy-transfer(DA-ET) system is investigated by the irradiation of Ar^ laser on its solid film.A reverse saturable absorption and an enhanced second reverse saturable absorption called the rereverse saturable absorption are observed in a visible wavelength range.The high performance of optical limiting of the sample possessing low input threshold and an over 95% linear transmission ratio are observed.The physical mechanism of rereverse satruable absorption is analysed by a five-level rate-equation simulating.According to the Huygens wave diffraction principle and the combination of Kerr effect,thermo-optic effect and optical absorption variation,a mathematical model for the optical limiting of ZnTBP-CA-PhR film limiter is established and the theoretical simulating gives a good agreement with the experimental results.     

Magnetic Properties of a Mixed Spin-2 and Spin-5/2 Heisenberg Ferrimagnetic System on a Two-Dimensional Honeycomb Lattice： Green＇s Function Approach

The multisublattice Green＇s function technique is applied to study the magnetic properties of a mixed spin-2 and spin-5/2 Heisenberg ferrimagnetic system on a two-dimensional honeycomb lattice. The role of the different interactions in the Hamiltonian is explored. When only the nearest-neighbor interaction and the single-ion anisotropy are included, our results indicate that there are compensation points at finite temperatures. When the next-nearest-neighbor interaction exceeds a minimum value that depends on the other parameters in the Hamiltonian, the compensation point disappears. The next-nearest-neighbor interaction has the effect of changing the compensation temperature.     

Green's function of an electron in an external electromagnetic field

New field-theoretical representations are obtained for Green's function of an electron in an external electromagnetic field, making it possible to simplify its calculation substantially.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 33–37, February, 1982.     

电磁学中的格林函数

文章回顾了电磁学中的格林函数理论与格林函数方法。首先,引入标量波动方程对应的格林函数,并与信号系统中的冲击响应函数作类比。其次,引入矢量波动方程对应的并矢格林函数,包括均匀和非均匀介质中的格林函数,并探讨其与电磁理论中的互易定理、等效原理之间的联系。最后,介绍了考虑介质的运动效应和电磁场的量子效应下的格林函数理论。此外,文章也探讨了电磁格林函数在无线通信、电磁兼容等工程领域的应用。     

Causal Green's function formalism in statistical mechanics of composite particles

A causal Green's function formalism is established within the framework of statistical mechanics of composite particles. It is shown that it provides a systematic way for calculating shift and broadening of atomic levels in partially ionized plasmas.     

The Green's function of confined electrons in an external magnetic field: Analytical formulation

We derive the analytical form of the Green's function of 2-dimensional electrons with lateral confinement in a perpendicular magnetic field. The confinement potentials considered are infinite barriers at radius R (quantum dot) and at r and R (quantum ring).     

Green's function for an electron in the field of a quantized wave

The Green's function for an electron in the field of a quantized free monochromatic wave is found. A method is proposed for constructing a complete orthonormal system of wave functions for this problem.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii. Fizika, No. 6, pp. 99–104, June, 1975.     

A local approach to dimensional reduction: I. General formalism

We present a formalism for dimensional reduction based on the local properties of invariant cross-sections (“fields”) and differential operators. This formalism does not need an ansatz for the invariant fields and is convenient when the reducing group is non-compact.

In the approach presented here, splittings of some exact sequences of vector bundles play a key role. In the case of invariant fields and differential operators, the invariance property leads to an explicit splitting of the corresponding sequences, i.e. to the reduced field/operator. There are also situations when the splittings do not come from invariance with respect to a group action but from some other conditions, which leads to a “non-canonical” reduction.

In a special case, studied in detail in the second part of this article, this method provides an algorithm for construction of conformally invariant fields and differential operators in Minkowski space.     

Green's function of a photon in an external electromagnetic field of a special kind

Photon interaction with a plane monochromatic, circularly polarized wave is investigated in the paper, being propagated along a permanent homogeneous magnetic field. Constraints are found that are imposed on the photon Green's function structure and polarization operator by the common demands of quantum electrodynamics and field symmetry. It is shown that a photon moving in the magnetic field direction can exchange not more than two of its quanta with the external wave.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 3–7, August, 1984.The author is grateful to I. M. Ternov, V. R. Khalilov, A. R. Frenkin, and A. E. Shabad for discussing the results of the research.     

Exact Green's function of the equations of quantum mechanics in an electromagnetic field. I

An exact Green's function of the Cauchy problem in arbitrary (nonparallel) stationary homogeneous electrical and magnetic fields is constructed for the Klein-Gordon-Fock and Dirac equations and for the Pauli equation in arbitrary nonstationary fields, on the basis of a single approach using the method of the canonical Maslov operator (extension of the WKB method to the multidimensional case) and a Fock idea about the proper time in relativitic mechanics.