Character of normal light waves in absorbing crystals with modulated dielectric parameters

Abstract

On the basis of the superposition principle for the optical anisotropy parameters and the Jones calculus methods a phenomenological model is developed to interpret the optical properties of absorbing, spatially modulated dielectric materials. The character of the normal electromagnetic waves propagated in a uniaxial, weakly dichroic crystal for which the complex gyration tensor is modulated with the simple square wave form is ascertained. The structure with a perfect modulation wave and the unipolar structure are considered and should describe the multidomain ferroelectric and incommensurately modulated phases. Specific crystal optical effects are found which have no analogues in uniform materials. Proceeding from the normal wave polarization the modulated crystal is shown to be equivalent to a low-symmetry biaxial crystal. The origin of a non-zero eigenwave ellipticity is discussed in connection with the problem of optical activity in macroscopically centrosymmetric incommensurate crystals of A 2 BX 4 group.

On the Propagation of Light in Incommensurately Modulated Dielectric Crystals

“…In order to clarify the manifestations of incommensurate modulation in experiments, we shall use the method suggested in [8,19] and pass in our analysis to effective crystal optical parameters which characterize the entire crystal plate of a finite thickness d. In this manner, one obains from (13) the ellipticity c of the effective normal waves that describes the macroscopic optical activity:…”

Spatial dispersion in incommensurately modulated insulators

“…The waves turn out to be elliptically polarized in general, the maximum ellipticity being achieved at the points where qz = ±π/2. Starting from the above, it is expedient to qualify the medium as optically active, although it could not be completely fitted into the common definitions of gyration for homogeneous media from the viewpoints of the 'quasi-local' CR and the normal wave polarization (see also the discussion in [22]).…”

“…With (22), Fourier transforming formula (20) leads to the CR in the wavevector domain (see appendix B):…”

“…Unlike in the present work, the microscopic dielectric Fourier components in chapter 2 of [2] appear (in our notation) as εh 0 i j (k). This is caused by the expansion of a periodic response function in the r variable but not in 1 2 (r + r ) (cf formula (22)). This result contradicts the Onsager principle and disregards a possible material SD.…”

Transmission matrix of a uniaxial optically active crystal platelet

“…Two methods are currently used to describe the effect of the crystal optical activity on plane wave propagation. The first one is phenomenological and is valid under normal incidence [2,3,4,5,6,7]. The second one is a first principle method and consists in solving the Maxwell equations with modified constitutive equations [1,8,9,10] (i.e.…”