АМПЛИТУДНАЯ МОДУЛЯЦИЯ СВЕТА ПУТЕМ ЭЛЕКТРООПТИЧЕСКОГО УПРАВЛЕНИЯ МНОГОЛУЧЕВОЙ ИНТЕРФЕРЕНЦИЕЙ В ИНТЕРФЕРОМЕТРЕ ФАБРИ–ПЕРО

In present work the questions related to decreasing the control voltage of amplitude Fabry–Perot modulators with conserving their high efficiency have been considered. Schematic models of high-efficient amplitude Fabry–Perot electrooptical modulators have been proposed.В настоящей работе были рассмотрены вопросы, связанные с уменьшением управляющего напряжения амплитудных модуляторов Фабри–Перо с сохранением их высокой эффективности. Были предложены схематические модели высокоэффективных амплитудных электрооптических модуляторов Фабри–Перо

ВЫСОКОЭФФЕКТИВНЫЙ АМПЛИТУДНЫЙ МОДУЛЯТОР НЕПОЛЯРИЗОВАННОГО ИЗЛУЧЕНИЯ С ПОПЕРЕЧНЫМ ЭЛЕКТРООПТИЧЕСКИМ ЭФФЕКТОМ

This article proposes a method for high-amplitude modulation of non-polarized radiation on the basis of the transverse electrooptic effect. The essence of the method is to minimize the effect of temperature changes in the electro-optical elements due to their parallel location in the insulating housing having high thermal conductivity. An amplitude electro-optic modulator with a cross application of control field KTP crystals made according to the ring scheme is described.Предлагается метод высокоэффективной амплитудной модуляции неполяризованного излучения на базе поперечного электрооптического эффекта, сущность которого заключается в минимизации влияния температурных изменений в электрооптических элементах за счет их параллельного размещения в диэлектрическом корпусе, обладающем высокой теплопроводностью. Описан амплитудный электрооптический модулятор с поперечным приложением управляющего поля кристаллов КТР, выполненный по кольцевой схеме

Magnetic structures and reorientation transitions in noncentrosymmetric uniaxial antiferromagnets

A phenomenological theory of magnetic states in noncentrosymmetric tetragonal antiferromagnets is developed, which has to include homogeneous and inhomogeneous terms (Lifshitz-invariants) derived from Dzyaloshinskii-Moriya couplings. Magnetic properties of this class of antiferromagnets with low crystal symmetry are discussed in relation to its first known members, the recently detected compounds Ba2CuGe2O7 and K2V3O8. Crystallographic symmetry and magnetic ordering in these systems allow the simultaneous occurrence of chiral inhomogeneous magnetic structures and weak ferromagnetism. New types of incommensurate magnetic structures are possible, namely, chiral helices with rotation of staggered magnetization and oscillations of the total magnetization. Field-induced reorientation transitions into modulated states have been studied and corresponding phase diagrams are constructed. Structures of magnetic defects (domain-walls and vortices) are discussed. In particular, vortices, i.e. localized non-singular line defects, are stabilized by the inhomogeneous Dzyaloshinskii-Moriya interactions in uniaxial noncentrosymmetric antiferromagnets.Comment: 18 pages RevTeX4, 13 figure

Changes to the Fossil Record of Insects through Fifteen Years of Discovery

The first and last occurrences of hexapod families in the fossil record are compiled from publications up to end-2009. The major features of these data are compared with those of previous datasets (1993 and 1994). About a third of families (>400) are new to the fossil record since 1994, over half of the earlier, existing families have experienced changes in their known stratigraphic range and only about ten percent have unchanged ranges. Despite these significant additions to knowledge, the broad pattern of described richness through time remains similar, with described richness increasing steadily through geological history and a shift in dominant taxa, from Palaeoptera and Polyneoptera to Paraneoptera and Holometabola, after the Palaeozoic. However, after detrending, described richness is not well correlated with the earlier datasets, indicating significant changes in shorter-term patterns. There is reduced Palaeozoic richness, peaking at a different time, and a less pronounced Permian decline. A pronounced Triassic peak and decline is shown, and the plateau from the mid Early Cretaceous to the end of the period remains, albeit at substantially higher richness compared to earlier datasets. Origination and extinction rates are broadly similar to before, with a broad decline in both through time but episodic peaks, including end-Permian turnover. Origination more consistently exceeds extinction compared to previous datasets and exceptions are mainly in the Palaeozoic. These changes suggest that some inferences about causal mechanisms in insect macroevolution are likely to differ as well

Minimizing the influence of temperature changes in the environment on the performance criteria of thermo-optical processor based on fabri-perot and smith microresonator

In this work, a mathematical model was created with the help of which the conditions were obtained under which the dependence of the light flux of the readout radiation reflected by Fabry-Perot and Smith microcavities minimally depends on the initial temperature of the resonator