Gyrotropic Crystals Research Articles

Optical activity of imperfect 1D superlattices with vacancies in impurity layers

The concentration dependence of the specific rotation angle of a gyrotropic photonic crystal (imperfect 1D superlattice with an arbitrary number of sublattices one of which (potassium dithionate K2S2O6) is optically active) is numerically simulated. Specific gyrotropic features of the photonic crystal related to the random substitution of layers of a model molecular crystal with vacancies for the layers of the K2S2O6 sublattice are revealed using microscopic analysis of the specific rotation angle of the optical polarization in the molecular crystal with a primitive lattice in the exciton spectral range.

On the role of symmetries in the theory of photonic crystals

We discuss the role of the symmetries in photonic crystals and classify them according to the Cartan–Altland–Zirnbauer scheme. Of particular importance are complex conjugation C and time-reversal T, but we identify also other significant symmetries. Borrowing the jargon of the classification theory of topological insulators, we show that C is a “particle–hole-type symmetry” rather than a “time-reversal symmetry” if one considers the Maxwell operator in the first-order formalism where the dynamical Maxwell equations can be rewritten as a Schrödinger equation; The symmetry which implements physical time-reversal is a “chiral-type symmetry”. We justify by an analysis of the band structure why the first-order formalism seems to be more advantageous than the second-order formalism. Moreover, based on the Schrödinger formalism, we introduce a class of effective (tight-binding) models called Maxwell–Harper operators. Some considerations about the breaking of the “particle–hole-type symmetry” in the case of gyrotropic crystals are added at the end of this paper.

Splitting of cones of optical axes in gyrotropic crystals in the presence of dichroism

Features of the appearance of conical singularities in the presence of linear dichroism and natural optical activity at the point of intersection of dispersion curves of the principal refractive indices of a crystal have been considered. It has been shown that even insignificant dichroism results in the splitting of cones of optical axes into cones of singular optical axes (in a partial case, cones are degenerate into planes) between which a “gap” with identical velocities of proper waves appears. The splitting angle for the AgGaS2 crystal is estimated at about 5°.

The Optics of Gyrotropic Crystals in the Field of Two Counter-Propagating Ultrasound Waves

We consider oblique light propagation through a layer of a gyrotropic crystal in the field of two counter-propagating ultrasound waves. The problem is solved by Ambartsumyan's layer addition modified method. The results of the reflection spectra for different values of the problem parameters are presented. The possibilities of such system applications are discussed.

Polarization-Independent Acousto-Optical Modulation of Bessel Light Beams

The acousto-optical diffraction of Bessel light beams (BLB) propagating near the optical axis of uniaxial gyrotropic crystals is examined. It is shown that polarization-independent modulation of Bessel beams is possible in paratellurite crystals; that is, the Bragg diffraction efficiency is independent of the polarization state of the incident beam. The physical reason for this kind of modulation is found to be the simultaneous occurrence of two anisotropic diffraction processes, such that the conditions for Bragg synchrony are satisfied for orthogonally polarized elliptical Bessel beams. The coupled wave equations and an overlap integral method are used to study the dependence of the diffraction efficiency on the length of the acousto-optical interaction, the ultrasonic power, and the polarization state of the incident Bessel beam.

Optical properties of gyrotropic crystals in the field of counterpropagating ultrasound waves

The oblique propagation of light through a gyrotropic crystal layer placed in the field of two counterpropagating ultrasound waves is considered. The problem is solved using Ambartsumian’s layer addition modified method. The results of studying the dependences of the amplitude and polarization characteristics on the light wavelength for different values of the problem parameters are presented. Possibilities of applications of such systems are discussed.

Peculiarities of propagation of electromagnetic excitation through a nonideal gyrotropic photonic crystal

The paper is devoted to numerical modeling of the rotatory power of gyrotropic photonic crystals doped with impurity layers. The model crystal is assumed to be a nonideal one-dimensional superlattice whose even (or odd) layers are formed of optically active potassium dithionate K2S2O6 and are randomly substituted by layers of a molecular crystal with vacancies. Peculiarities of the dependence of the specific optical rotation of the described structure on concentration of impurity layers are studied in the excitonic spectral range on the basis of a microscopic approach.

Formation of the two-dimensional contour of an image during triple Bragg diffraction

The possibility of formation of the 2D contour of an optical image in the first diffraction order during triple Bragg diffraction is first proposed and experimentally confirmed. Transfer functions are obtained as part of the developed model of 3D acousto-optical interaction in the gyrotropic crystal. The transfer function of the first diffraction order made it possible to identify the contour of a 2D image during its Fourier processing. These theoretical results are confirmed experimentally using triple Bragg diffraction occurring in a TeO2 monocrystal.

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.

Topological aspects in the photonic-crystal analog of single-particle transport in quantum Hall systems

We present a perturbative approach to derive the semiclassical equations of motion for the two-dimensional electron dynamics under the simultaneous presence of static electric and magnetic fields, where the quantized Hall conductance is known to be directly related to the topological properties of translationally invariant magnetic Bloch bands. In close analogy to this approach, we develop a perturbative theory of two-dimensional photonic transport in gyrotropic photonic crystals to mimic the physics of quantum Hall systems. We show that a suitable permittivity grading of a gyrotropic photonic crystal is able to simulate the simultaneous presence of analog electric and magnetic field forces for photons, and we rigorously derive the topology-related term in the equation for the electromagnetic energy velocity that is formally equivalent to the electronic case. A possible experimental configuration is proposed to observe a bulk photonic analog to the quantum Hall physics in graded gyromagnetic photonic crystals.

Light diffraction by acoustophotorefractive dynamic gratings in Raman―Nath regime

Raman–Nath light diffraction on acoustophotorefractive holographic gratings that was recorded in cubic photorefractive crystals according to a synchronous detection mechanism was investigated. It was shown that the diffraction efficiency in sillenite-type gyrotropic crystals depended weakly on the incident light polarization and the external electric field strength. The highest diffraction efficiency in non-gyrotropic crystals was reached for p-polarized light (writing and reading) and a strong external electric field.

Polarization features of the 2D contouring of an optical image under double Bragg diffraction conditions

The polarization features concerning the formation of a 2D image contour in the first diffraction order, which arise from the double Bragg diffraction occurring in the uniaxial gyrotropic crystal, are investigated. It is demonstrated that changes in sound power make it possible to create 2D image contours in different polarization states. Experiments based on the double diffraction in the TeO2 crystal have confirmed the basic theoretical assumptions.

Two-dimensional image edge enhancement by two-phonon Bragg diffraction

A model of acousto-optic interaction is developed for describing two-phonon Bragg diffraction in a gyrotropic single TeO2 crystal, which makes allowance for ellipticity of crystal opticaleigenwaves. Formation of a two-dimensional edge of an image in the first diffraction order is explained by invoking a three-dimensional description for the wave surfaces of optical eigenwaves.

Space polarization and nonlinear absorbability of gyrotropic cadmium diphosphide crystals

AbstractTwo‐photon absorption coefficient of cadmium diphosphide single crystals have been measured depending on a polarization azimuth (ϕ) at extreme light intensities near the optical damage threshold (11 MW/cm2). It is shown that the maximum value of this coefficient is equal to 0.16 cm/MW at ϕ = 0 (for the ordinary wave). These dependences are important for producing of the quantum electronics and nonlinear optics elements based on the effect of two‐photon absorption under extreme condition (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Parity-time electromagnetic diodes in a two-dimensional nonreciprocal photonic crystal

We propose a kind of electromagnetic (EM) diode based on a two-dimensional nonreciprocal gyrotropic photonic crystal. This periodic microstructure has separately broken symmetries in both parity (P) and time-reversal (T) but obeys parity-time (PT) symmetry. This kind of diode could support bulk one-way propagating modes either for group velocity or phase velocity with various types of negative and positive refraction. This symmetry-broken system could be a platform to realize abnormal photoelectronic devices, and it may be analogous to an electron counterpart with one-way features.

Partial Reciprocity of Faraday Rotation in Gyrotropic Crystals

It is shown that under the conditions of coexistence of the natural optical activity and some non-zero linear optical birefringence a partial non-reciprocity of the Faraday rotation can appear in transparent, optically quasi-uniaxial crystals. In particular, such the conditions may be reached in optically uniaxial crystals that manifest some residual linear birefringence along the optic axis direction. The theoretical prediction well agrees with obtained experimental results.

Reflection spectra of NaClO3, NaBrO3, and LiIO3 gyrotropic crystals in the vacuum UV region

The reflection spectra in the fundamental-absorption region, 5–25 eV (250–40 nm), of optically active crystals with cubic symmetry (NaClO3, NaBrO3) and uniaxial optically active crystal (LiIO3) have been investigated. It is shown that the reflection spectra of cubic crystals have a similar structure, which is determined by the electronic transitions in the XO3 group. The comparison of these spectra with the corresponding spectrum of lithium iodide made it possible to determine the type of transition in the spectra of cubic crystals. Using the projection operator method, it was shown that the sign of optical rotation of cubic crystals with symmetry T is independent of the screw axis sign. Possible reasons for the unprecedentedy large optical rotation of lithium iodide crystal in the optical axis direction are considered.

Polariton dynamics of a one-dimensional gyrotropic magnetic photonic crystal in a dc electric field: II. Surface waves

Localization and dispersion of collective magnetic TE and TM polaritons are analyzed for a semi-infinite, one-dimensional, magnetic photonic crystal of the compensated antiferromagnetic-nonmagnetic dielectric type in the presence of orthogonal magnetic and electric fields. The case where easy magnetization axis is orthogonal to the external electric field is considered.

Polariton dynamics of a one-dimensional gyrotropic magnetic photonic crystal in a dc electric field: I. Peculiarities of refraction

It is shown that both TE and TM waves incident on the surface of a semi-infinite one-dimensional thin-layer gyrotropic magnetic photonic crystal of the magnetic-nonmagnetic dielectric type can experience a number of refraction anomalies in an external electric field due to the effect of hybridization of evanescent waves in magnetic and nonmagnetic layers. These anomalies are absent under the same conditions in spatially homogeneous media consisting of the same materials as the photonic crystal.

Electric-field-induced features of propagation and localization of S-polaritons in a gyrotropic 1D magnetic photonic crystal

The effect of the quadratic magnetooptical interaction on the refraction of volume electromagnetic TE waves incident from outside onto the surface of a 1D photonic crystal of the easy-axis ferromagnet-nonmagnetic dielectric type in an external dc electric field.