Oblique frozen modes in periodic layered media

We study the classical scattering problem of a plane electromagnetic wave incident on the surface of semi-infinite periodic stratified media incorporating anisotropic dielectric layers with special oblique orientation of the anisotropy axes. We demonstrate that an obliquely incident light, upon entering the periodic slab, gets converted into an abnormal grazing mode with huge amplitude and zero normal component of the group velocity. This mode cannot be represented as a superposition of extended and evanescent contributions. Instead, it is related to a general (non-Bloch) Floquet eigenmode with the amplitude diverging linearly with the distance from the slab boundary. Remarkably, the slab reflectivity in such a situation can be very low, which means an almost 100% conversion of the incident light into the axially frozen mode with the electromagnetic energy density exceeding that of the incident wave by several orders of magnitude. The effect can be realized at any desirable frequency, including optical and UV frequency range. The only essential physical requirement is the presence of dielectric layers with proper oblique orientation of the anisotropy axes. Some practical aspects of this phenomenon are considered.Comment: text and 9 figure

Metamaterials proposed as perfect magnetoelectrics

Magnetoelectric susceptibility of a metamaterial built from split ring resonators have been investigated both experimentally and within an equivalent circuit model. The absolute values have been shown to exceed by two orders of magnitude that of classical magnetoelectric materials. The metamaterial investigated reaches the theoretically predicted value of the magnetoelectric susceptibility which is equal to the geometric average of the electric and magnetic susceptibilities.Comment: 5 pages, 3 figure

Photoinduced 3D orientational order in side chain liquid crystalline azopolymers

We apply experimental technique based on the combination of methods dealing with principal refractive indices and absorption coefficients to study the photoinduced 3D orientational order in the films of liquid crystalline (LC) azopolymers. The technique is used to identify 3D orientational configurations of trans azobenzene chromophores and to characterize the degree of ordering in terms of order parameters. We study two types of LC azopolymers which form structures with preferred in-plane and out-of-plane alignment of azochromophores, correspondingly. Using irradiation with the polarized light of two different wavelengths we find that the kinetics of photoinduced anisotropy can be dominated by either photo-reorientation or photoselection mechanisms depending on the wavelength. We formulate the phenomenological model describing the kinetics of photoinduced anisotropy in terms of the isomer concentrations and the order parameter tensor. We present the numerical results for absorption coefficients that are found to be in good agreement with the experimental data. The model is also used to interpret the effect of changing the mechanism with the wavelength of the pumping light.Comment: uses revtex4 28 pages, 10 figure

Proximity induced metal/insulator transition in YBa2Cu3O7/La2/3Ca1/3MnO3Y Ba_2 Cu_3 O_7 / La_{2/3} Ca_{1/3} Mn O_3 superlattices

The far-infrared dielectric response of superlattices (SL) composed of superconducting YBa$_{2}$Cu$_{3}$O$_{7}$ (YBCO) and ferromagnetic La$_{0.67}$% Ca$_{0.33}$MnO$_{3}$ (LCMO) has been investigated by ellipsometry. A drastic decrease of the free carrier response is observed which involves an unusually large length scale of d$^{crit}\approx$20 nm in YBCO and d$^{crit}\approx$10 nm in LCMO. A corresponding suppression of metallicity is not observed in SLs where LCMO is replaced by the paramagnetic metal LaNiO$_{3}$. Our data suggest that either a long range charge transfer from the YBCO to the LCMO layers or alternatively a strong coupling of the charge carriers to the different and competitive kind of magnetic correlations in the LCMO and YBCO layers are at the heart of the observed metal/insulator transition. The low free carrier response observed in the far-infrared dielectric response of the magnetic superconductor RuSr$_{2}$GdCu$_{2}$O$_{8}$ is possibly related to this effect

ANOMALOUS STIFFNESS AND TILT ANGLE IN NEMATICS FROM NONUNIFORM ATTACHMENT ANGLE

Si, dans un cristal liquide nématique, la constante d'élasticité de déformation en éventail k11 et la constante d'élasticité de flexion k33 sont dissemblables, et si les directeurs immédiatement adjacents à la surface sont fixés rigidement dans des directions non uniformes, alors les constantes apparentes k33 et k11 très proches de la surface seront modifiées par un effet de moyenne. Si des molécules de cristaux liquides tels que MBBA, ayant k11 k33, le signe de l'anomalie en épaisseur est inversé. Si l'angle moyen d'ancrage à la surface n'est ni homéotrope, ni parallèle, alors, en l'absence d'un champ appliqué, l'angle d'inclinaison au-delà de la zone de surface déformée dépend aussi du rapport k11/k33. Pour des variations qui ne sont pas coplanaires, les résultats dépendent aussi de la constante de torsion k22, mais les effets sont qualitativement les mêmes. Des simulations par ordinateur sont présentées en illustration.If the splay elastic constant k11 and the band elastic constant k33 in a nematic liquid crystal are unlike, and if the directors immediately adjacent to the surface are rigidly attached in nonuniform directions then the apparent bend and splay constants very near the surface will be altered by an averaging effect. If liquid crystals such as MBBA, having k11 k33, the sign of the thickness anomaly is reversed. If the average angle of surface attachment is not homeotropic or parallel, then in the absence of an applied field the tilt angle beyond the distorted surface region also depends on k11/k33. For variations that are not coplanar results also depend on the twist constant, k22, but the trends are the same. Computer generated illustrations are presented