In this paper we develop a computational method for photonic band structures with active and conductive media by transforming Maxwell's equations into high-order nonlinear polynomial eigensystems based on the plan...
详细信息
In this paper we develop a computational method for photonic band structures with active and conductive media by transforming Maxwell's equations into high-order nonlinear polynomial eigensystems based on the plane-wave expansion method with complex k vectors. Furthermore, by assuming an infinitely fast response of the material, we reduce the high-order polynomial eigensystems to lower-order (ordinary or quadratic) eigenproblems. Numerical computations were performed at point L for the fcc lattice structure with active nonconducting and nonactive conducting dielectric media by solution of the ordinary or linearized eigensystems. For both cases physical solutions with complex k vectors for Maxwell's equations were found between the two propagating modes;however, solutions were in the unphysical region of the tunneling dispersion relation for the passive media.
作者：
HAMAM, HDELATOCNAYE, JLDB[]Departement d’Optique
Unité de Recherche Associée Centre National de la Recherche Scientifique 1329 Ecole Nationale Supérieure des Télécommunications de Bretagne B.P. 832 29285 Brest Cedex France
The efficient Fresnel-transform algorithm (EFTA) is a computational tool that facilitates diffracted field analysis. The computational improvement that is achieved with the EFTA relative to the conventional double fas...
详细信息
The efficient Fresnel-transform algorithm (EFTA) is a computational tool that facilitates diffracted field analysis. The computational improvement that is achieved with the EFTA relative to the conventional double fast-Fourier-transform (FFT) algorithm results from the properties of fractional Fresnel diffraction. Some programming simplicities are shown to appear at numerous locations along the propagation axis. The number of those locations is determined by the fractional order. Some computational aspects of the method are presented and compared with those of the FFT algorithm.
The combination of complex scaling with the (t, t') representation of the time-dependent Schrodinger equation [J. Chem. Phys. 99, 4590 (1993)] permits the design of graded-index multimode fiber to control the dist...
详细信息
The combination of complex scaling with the (t, t') representation of the time-dependent Schrodinger equation [J. Chem. Phys. 99, 4590 (1993)] permits the design of graded-index multimode fiber to control the distribution of power among the modes. The differential modal losses are associated with the imaginary parts of the complex eigenvalues of a complex scaled Floquet-type operator. Although the illustrative numerical calculations are given here for the case in which the index of refraction is periodically varied along the fiber axis, the method is applicable for a more general coordinate-dependent index-of-refraction case.
A vector perturbation model for computing optical fiber birefringence for an arbitrary two-dimensional index profile is developed. The vector wave equation is solved to yield the unperturbed vector fields for an azimu...
详细信息
A vector perturbation model for computing optical fiber birefringence for an arbitrary two-dimensional index profile is developed. The vector wave equation is solved to yield the unperturbed vector fields for an azimuthally symmetric refractive index. These fields are used as the basis for the degenerate perturbation analysis. Unlike with the scalar perturbation theory, only first-order perturbation analysis suffices for the computation of birefringence. Computed birefringence for various perturbations are reported. (C) 1995 Optical Society of America
Modeling of the full temporal behavior of photons propagating in diffusive materials is computationally costly. Rather than deriving intensity as a function of time to fine sampling, we may consider methods that deriv...
详细信息
Modeling of the full temporal behavior of photons propagating in diffusive materials is computationally costly. Rather than deriving intensity as a function of time to fine sampling, we may consider methods that derive a transform of this function. To derive the Fourier transform involves calculation in the (complex) frequency domain and relates to intensity-modulated experiments. We consider instead the Mellin transform and show that this relates to the moments of the original temporal distribution. A derivation of the Mellin transform given the Fourier transform that permits closed-form derivations of the temporal moments for various simple geometries is presented. For general geometries a finite-element method is presented, and it is demonstrated that the computational cost to produce the nth moment is the same as producing the first n temporal samples of the original function.
This work describes a methodology for identification of skeletal types of diterpenes based on data base with 1500 compounds isolated from Asteraceae. One program named BOTOCSYS was built with the codification of the c...
详细信息
This work describes a methodology for identification of skeletal types of diterpenes based on data base with 1500 compounds isolated from Asteraceae. One program named BOTOCSYS was built with the codification of the compounds and their botanical sources. An example of identification of a new substance is given.
Synthetic near-field holograms with large apertures are suitable for three-dimensional display applications. For the computation of near-field hologram structures, algorithms that involve large Fourier transforms are ...
详细信息
Synthetic near-field holograms with large apertures are suitable for three-dimensional display applications. For the computation of near-field hologram structures, algorithms that involve large Fourier transforms are time consuming. A simple method is presented that shortens the generation process.
Electromagnetic fields associate energy with the structure of space and time, so that space and time jointly are constituents of the physical effects. The algebra of differential forms is well-suited to the descriptio...
详细信息
Electromagnetic fields associate energy with the structure of space and time, so that space and time jointly are constituents of the physical effects. The algebra of differential forms is well-suited to the description of such fields and greatly clarifies the processes, whereas the more usual vector algebra can lead to confusion and contradictions. The use of differential forms also points the way to simple methods of computation based on the geometrical shape of the fields rather than on the solution of differential equations. Amongst other advantages the geometrical methods provide upper and lower bounds for the system energy.
A new photometric-stereo method for estimating the surface normal and the surface reflectance of objects without a priori knowledge of the light-source direction or the light-source intensity is proposed. First, I con...
详细信息
A new photometric-stereo method for estimating the surface normal and the surface reflectance of objects without a priori knowledge of the light-source direction or the light-source intensity is proposed. First, I construct a p x f image data matrix I from p pixel image intensity data through f frames by moving a light source arbitrarily. Under the Lambertian assumption the image data matrix I can be written as the product of two matrices S and L, with S representing the surface normal and the surface reflectance and L representing the light-source direction and the Light-source intensity. Using this formulation, I show that the image data matrix I is of rank 3. On the basis of this observation, I use a singular-value decomposition technique and useful constraints to factorize the image data matrix. This method can also be used to treat cast shadows and self-shadows without assumptions. The effectiveness of this method is demonstrated through performance analysis, laboratory experiment, and out-of-laboratory experiment.
Interest in scattering and/or absorption involving three-dimensional penetrable bodies has driven numerous efforts to develop computational methods for such problems. When the object is geometrically and electrically ...
详细信息
Interest in scattering and/or absorption involving three-dimensional penetrable bodies has driven numerous efforts to develop computational methods for such problems. When the object is geometrically and electrically complex, the finite-element method is a logical numerical choice. Helmholtz weak forms have recently been advocated, and computational successes have been achieved with the approach. An overview of the Helmholtz formulation, with particular emphasis on its spurious-mode-resistant properties, some efficient and reliable solution procedures for the algebra that it generates, and an approach to unstructured mesh generation, is presented. As a whole these procedures provide the basis for a methodology for realizing three-dimensional finite-element solutions of Maxwell's equations in a workstation computing environment. Examples of calculations that demonstrate several important properties of the Helmholtz technique and illustrate the extent to which practical three-dimensional calculations can be accomplished with readily available computing power are shown.
暂无评论