Excitations in photonic crystals infiltrated with polarizable media

Journal ArticleLight propagation in a photonic crystal with incomplete band gap, infiltrated with polarizable molecules is considered. We demonstrate that the interplay between the spatial dispersion caused by Bragg diffraction and polaritonic frequency dispersion gives rise to alternative propagating excitations, or photonic-crystal-polaritons (PCP), with intragap frequencies. We derive the PCP dispersion relation and show that it is governed by two parameters, namely, the strength of light-matter interaction and detuning between the Bragg frequency and that of the infiltrated molecules. We also study defect-induced states when the photonic band gap is divided into two subgaps by the PCP branches and find that each defect creates two intragap localized states inside each subgap

Coherent umklapp scattering of light from disordered photonic crystals

Journal ArticleA theoretical study of the coherent light scattering from disordered photonic crystals is presented. In addition to the conventional enhancement of the reflected light intensity into the backscattering direction, the so-called coherent backscattering (CBS), the periodic modulation of the dielectric function in photonic crystals gives rise to a qualitatively new effect: enhancement of the reflected light intensity in directions different from the backscattering direction. These additional coherent scattering processes, dubbed here umklapp scattering (CUS), result in peaks, which are most pronounced when the incident light beam enters the sample at an angle close to the the Bragg angle. Assuming that the dielectric function modulation is weak, we study the shape of the CUS peaks for different relative lengths of the modulation-induced Bragg attenuation compared to the disorder-induced mean free path. We show that when the Bragg length increases, then the CBS peak assumes its conventional shape, whereas the CUS peak rapidly diminishes in amplitude. We also study the suppression of the CUS peak upon the departure of the incident beam from the Bragg resonance: we found that the diminishing of the CUS intensity is accompanied by substantial broadening. In addition, the peak becomes asymmetric

Charged mobile complexes in magnetic fields: A novel selection rule for magneto-optical transitions

The implications of magnetic translations for internal optical transitions of charged mobile electron-hole ($e$--$h$) complexes and ions in a uniform magnetic field $B$ are discussed. It is shown that transitions of such complexes are governed by a novel exact selection rule. Internal intraband transitions of two-dimensional (2D) charged excitons $X^-$ in strong magnetic fields are considered as an illustrative example.Comment: 4 pages, 2 figure

Coherent Umklapp Scattering of Light from Disordered Photonic Crystals

A theoretical study of the coherent light scattering from disordered photonic crystal is presented. In addition to the conventional enhancement of the reflected light intensity into the backscattering direction, the so called coherent backscattering (CBS), the periodic modulation of the dielectric function in photonic crystals gives rise to a qualitatively new effect: enhancement of the reflected light intensity in directions different from the backscattering direction. These additional coherent scattering processes, dubbed here {\em umklapp scattering} (CUS), result in peaks, which are most pronounced when the incident light beam enters the sample at an angle close to the the Bragg angle. Assuming that the dielectric function modulation is weak, we study the shape of the CUS peaks for different relative lengths of the modulation-induced Bragg attenuation compared to disorder-induced mean free path. We show that when the Bragg length increases, then the CBS peak assumes its conventional shape, whereas the CUS peak rapidly diminishes in amplitude. We also study the suppression of the CUS peak upon the departure of the incident beam from Bragg resonance: we found that the diminishing of the CUS intensity is accompanied by substantial broadening. In addition, the peak becomes asymmetric.Comment: LaTeX, 8 two-column pages, 6 figures include

Braggoriton--Excitation in Photonic Crystal Infiltrated with Polarizable Medium

Light propagation in a photonic crystal infiltrated with polarizable molecules is considered. We demonstrate that the interplay between the spatial dispersion caused by Bragg diffraction and polaritonic frequency dispersion gives rise to novel propagating excitations, or braggoritons, with intragap frequencies. We derive the braggoriton dispersion relation and show that it is governed by two parameters, namely, the strength of light-matter interaction and detuning between the Bragg frequency and that of the infiltrated molecules. We also study defect-induced states when the photonic band gap is divided into two subgaps by the braggoritonic branches and find that each defect creates two intragap localized states inside each subgap.Comment: LaTeX, 8 pages, 5 figure

ВИЧ-ИНФЕКЦИЯ И ВИЧ-АССОЦИИРОВАННЫЙ ТУБЕРКУЛЕЗ У ДЕТЕЙ УКРАИНЫ

The article presents data on the epidemiology of HIV infection and co-infection with HIV/TB in children in Ukraine. Along with the increasing number of HIV-infected women of reproductive age and their children, it is mentioned the growth of tuberculosis among HIV-infected children. The problems of adequate monitoring and management of these patients, in particular with regard to the prevention of tuberculosis among them are described. There are made conclusions about the need to improve the delivery system of TB care for children born by HIV-infected mothers.В статье представлены данные об эпидемиологической ситуации по ВИЧ-инфекции и ко-инфекции ВИЧ/туберкулез у детей на Украине. Наряду с увеличением числа ВИЧ-инфицированных женщин детородного возраста и рожденных ими детей отмечен рост заболеваемости туберкулезом среди ВИЧ-инфицированных детей. Освещаются вопросы адекватного наблюдения и ведения этой категории пациентов, в частности трудности профилактики у них туберкулеза. Сделаны выводы о необходимости совершенствования системы оказания противотуберкулезной помощи детям, рожденным от ВИЧ-инфицированных матерей