RESUMO
Uniaxial anisotropy in nonlinear birefringent crystals limits the efficiency of nonlinear optical interactions and breaks the spatial symmetry of light generated in the parametric down-conversion (PDC) process. Therefore, this effect is usually undesirable and must be compensated for. However, high gain may be used to overcome the destructive role of anisotropy in order to generate bright two-mode correlated twin-beams. In this work, we provide a rigorous theoretical description of the spatial properties of bright squeezed light in the presence of strong anisotropy. We investigate a single crystal and a system of two crystals with an air gap (corresponding to a nonlinear SU(1,1) interferometer) and demonstrate the generation of bright correlated twin-beams in such configurations at high gain due to anisotropy. We explore the mode structure of the generated light and show how anisotropy, together with crystal spacing, can be used for radiation shaping.
RESUMO
Altogether 700 patients suffering from epilepsy were examined. Of these, 49 patients (7%) were with a history of affective respiratory attacks (ARA) and constituted a catamnestic group. The control group included 110 patients with ARA. The clinical varieties of ARA, associated ARA and epilepsy and ARA differences as dependent on the sex are described. ARA outcomes are demonstrated in patients of early school age. Comparison of the catamnestic and control groups in terms of the intensity of perinatal aggravation, neurological and intellectual disorders revealed a significantly higher frequency in the catamnestic group. No material differences were revealed in hereditary aggravation. ARA are regarded as one of the manifestations of paroxysmal responsiveness in childhood with a high risk of the development later on of epilepsy and other psychoneurological diseases.