THE COMPETITION OF BRAGG REFLECTION AND FRESNEL'S REFLECTION OF ELECTROMAGNETIC WAVES IN THE ARTIFICIAL HELICOIDAL BIANISOTROPIC MEDIA WITH LOCAL CHIRALITY 1. V. SEMCHENKO and S. A. KHAKHOMOV Department of General Physics, Gamel State University Sovyetskaya Str. 104, 246019, Gamel, Belarus Abstract . On the base of the exact solution of the boundary-value problem for artificial helicoidal media with local chirality we describe the reflection of electromagnetic waves on the periodic structure of medium as well as Fresnel's reflection from sample's boundaries. It allows to model the transmission and reflection of electromagnetic waves in dependence on the obtained parameters of artificial helicoidal medium and to design the device for polarization transformation. A possibility of the minimizing of size of a structure for transformations of the polarization state of electromagnetic waves is shown. 1. Introduction In paper [1] was shown a possibility of the design of a structure whose mi- crowave properties are similar to the optical properties of cholesteric liquid crystals. This structure also exhibits local chirality because it contains the small wire helices. Such a structure can be a multilayer anisotropic chiral sample. When the number of layers increases, the helices turn at a constant angle around the axis which is perpendicular to the planar (see Fig. 1). As a result the sample as a whole acquires a macroscopic helicoidal structure which is analogical to the structure of cholesteric liquid crystals. Methods to design and manufacture artificial chiral media with uniaxial homogeneous structure were described in [2] . It was proposed to wind thin wires around Nylon threads, to align these helices and then to cast them into epoxy resin. In this case the permittivity and chirality of the effective medium are characterized by uniaxial tensors, the axis of which is oriented along the direction of the parallel Nylon threads. The axis of the macroscopic helicoidal structure is orthogonal to both the boundaries of the layers and the Nylon lines (see Fig. 1), i.e., to the local optical axes oflayers. 307 S. Zouhdi et al. [eds.), Advances in Electromagnetics a/Complex Media and Metamaterials, 307-318. © 2003 KluwerAcademic Publishers. Printed in the Netherlands.