Fresnel diffraction on the edge of causality

Taking advantage of the slow optical response of low-temperature rare earth ion-doped crystal, we explore the similarity between causality and Fresnel diffraction by a straight edge. We relate these features to spectral resolution and selectivity. The concept is illustrated with experimental data.     

Double-slit experiment and Bogoliubov’s causality principle

In the Bogoliubov approach the causality principle is the basic constructive element of quantum field theory. At the same time, this principle has obvious classical interpretation. On the other hand, it is well-known Feynman statement that the double-slit experiment is “impossible, absolutely impossible to explain in classical way, and has in it the heart of quantum mechanics. We describe how taking into account of infrared singularities allows to give quite evident interpretation to double-slit experiment. And this interpretation agrees with the Bogoliubov’s causality principle.     

The causality principle in relativistic gravitation theory

It is shown that relativistic gravitation theory is consistent with the existence of vacuum-like medium. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 20–25, April, 2007.     

The principle of causality in acoustic double-negative media

We discuss double negative acoustic media with various types of dispersion. The absence of dispersion leads to violation of the causality principle. No strong absorption occurs and there is no violation of the principle of causality in a dispersive medium with resonant response.     

Inclusion of the causality principle in the dynamical description of nonequilibrium systems

In the nonequilibrium-statistical-operator (NSO) method a correction to the Hamiltonian of a system is found, corresponding to a source in the Liouville equation, which destroys the invariance of this equation with respect to time reversal. Analysis of this correction enables one to conclude that the forces leading to the irreversible behavior of a system are of an essentially nonpotential nature. Inclusion of the causality principle in the Hamiltonian of a system also makes it possible to give a new representation of the NSO.     

Numerical demonstration of three-dimensional terahertz metamaterials based on the causality principle

A parameter retrieval algorithm based on the causality principle and Kramers-Kronig （KK） relations is employed to calculate the effective parameters of three-dimensional （3D） metamaterials. Using KK relations, the branch selecting problem, which is the challenge of effective parameter retrieval method, can be removed. To reveal the validity of the proposed algorithm, the constitutive refractive index of a homogeneous polymide cube is extracted. The result is in excellent agreement with the intrinsic refractive index of the polymide. Finally, the two terahertz metamaterials with 3D structures are designed and their effective parameters are then retrieved using the proposed algorithm. Numerical simulations are performed using the fuiI-wave electromagnetic solver, CST Microwave Studio.     

On an application of the causality principle to the theory of ion transport processes

We suggest an approach for ion transport processes that is motivated by analogies with the S-matrix theory. By using causality-based analyticity assumptions, conductivity frequency pre-factors are expressed in terms of the transfer amplitude. This provides a means of dealing with a unified scheme that includes ionic oscillations in wells and classical-like escaping. As an application, we use this technique to reproduce results obtained in terms of the Kramers problem without invoking the Kramers’ Fokker-Planck equation or details of the transfer mechanism in solid electrolytes.     

Light diffraction on ultrasonic Love waves

It is shown that layers based on acoustooptic crystals excited by ultrasonic Love waves can be used as light modulators in the reflection and transmission mode. It is established that various modes of Love waves can be detected by optical methods. For small ultrasound intensities, the diffraction efficiency is determined by the degree of homogeneity of deformations within the layer, and for large intensities, by the length of the acoustooptic interaction.     

Light diffraction on acoustophotorefractive holographic gratings

The intermediate regime of light diffraction on acoustophotorefractive holographic gratings written in cubic photorefractive crystals according to the synchronous-detection mechanism is studied. It is shown that the diffraction efficiency in sillenite-type gyrotropic crystals only slightly depends on the incident light polarization and the external electric field. The highest diffraction efficiency in nongyrotropic crystals was achieved for p-polarized writing and reading light and at a considerable external electric field strength.     

Light diffraction effects from Kevlar aramid fibers

The light diffraction phenomenon from Kevlar 49 fibers exhibits unusual polarization effects and its angular and wavelength dependence cannot be described by the grating equation. This unexpected behavior is analyzed by modeling the fiber as an anisotropic grating of finite thickness in which the diffraction arises from a periodic change in the orientation of the molecular dipoles. Theoretical predictions on this basis explain all available experimental observations. These findings are discussed in regard to currently proposed structural models for the fiber.     

Babinet's principle in the Fraunhofer diffraction by a finite thin wire

The scattered waves by a thin finite wire are evaluated by using the Rayleigh-Sommerfeld integral in the Fraunhofer approximation. The scattered fields by the complementary thin wire are also obtained with the aid of the Babinet's principle. The scattering integrals are evaluated directly. It is shown that Babinet's principle holds excellently for this problem. The scattered fields are examined numerically.     

Light diffraction from the volume holograms in electrooptic birefringent crystals

Angular bandwidth of the image reconstructed from the volume phase hologram at a wavelength different from that of the recording beams has been analysed. An optimum holographic scheme on the basis of anisotropic diffraction uniting maximum bandwidth of the Gabor's scheme and advantages of the Leith-Upatnieks scheme has been proposed for non-destructive readout of the volume hologram in birefringent photorefractive crystals. The main results of the theoretical analysis leading to the optimum holographic arrangement for electrically controlled retrieval of information from the volume of the electrooptic crystal are presented. Demonstrating experiments has been performed with LiNbO₃: Fe crystals.     

Light diffraction by a strong standing electromagnetic wave

The nonlinear quantum interaction of a linearly polarized x-ray probe beam with a focused intense standing laser wave is studied theoretically. Because of the tight focusing of the standing laser pulse, diffraction effects arise for the probe beam as opposed to the corresponding plane wave scenario. A quantitative estimate for realistic experimental conditions of the ellipticity and the rotation of the main polarization plane acquired by the x-ray probe after the interaction shows that the implementation of such vacuum effects is feasible with future X-ray Free Electron Laser light.     

Light diffraction features in an ordered monolayer of spheres

The structure and optical diffraction properties of monolayers of monodisperse spheres crystallized on transparent dielectric substrates are studied. Two types of diffraction phenomena are considered: surface light diffraction on the lattice of spheres and waveguide resonances in the monolayer plane. For experimental study of these phenomena, optical retroreflection and transmission spectra are measured as functions of the light incidence angle and azimuthal orientation of the incidence plane. The monolayer structures determined by scanning electron microscopy and light diffraction methods are in quantitative agreement. It is concluded that one-dimensional Fraunhofer diffraction is applicable to describe surface diffraction in the hexagonal lattice of spheres. In the case of oblique light incidence, anisotropy of diffraction and transmission spectra depending on the light incidence plane orientation with respect to the sphere lattice and linear polarization of incident light is detected. Waveguide resonances of the planar two-dimensional photonic crystal are approximated within the light diffraction model in the “empty” hexagonal lattice. The best approximation of the waveguide resonance dispersion is achieved using the effective refractive index, depending on the wavelength. Surface diffraction suppression by waveguide resonances of the photonic crystal is demonstrated. Surface diffraction orders are identified as diffraction at singular points of the Brillouin zone of the planar twodimensional photonic crystal.     

Light modulation by acoustic signals for high diffraction efficiency

A theoretical discussion is presented on strong Bragg acoustooptic interaction AOI of light beams in the dynamic field of an acoustic signal. A system of integrodifferential equations is formulated to describe the evolution of the angular and frequency spectra of the beams in the AOI region for a high level of acoustooptic coupling. The third-order approximation in the perturbation method is used to obtain an analytic solution. Calculations are presented on the modulation of monochromatic beams by acoustic pulses having rectangular envelopes and propagating in a lithium niobate crystal, and the same for a signal having linear frequency modulation LFM in a paratellurite crystal, which demonstrate the broadening of the beam spectrum as the depth of the acoustooptic coupling increases, together with the occurrence of an asymmetry specific to strong AOI in the response of the light field to the symmetrical acoustic signal. Tomsk State University for Control Systems and Electronics, Tomsk. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, Vol. 42, No. 1, pp. 99–106, January, 1999.     

Rigorous solution for transient propagation of electromagnetic waves through a medium: causality plus diffraction in time

A rigorous solution for transient propagation of electromagnetic waves through a medium has been found. Because of this rigorousness, the solution exhibits apparent consistency with Einsteinian causality. Thus, it is confirmed that faster-than-light or superluminal propagation of electromagnetic waves is not possible. Evanescent transmission gives rise to diffraction in time, which is the actual reason for deformation of group propagation.