An analytical-numerical technique for the solution of the plane-wave scattering problem by a set of dielectric cylinders embedded in a dielectric slab is presented. Scattered fields are expressed by means of expansions into cylindrical functions, and the concept of plane-wave spectrum of a cylindrical function is employed to define reflection and transmission through the planar interfaces. Multiple reflection phenomena due to the presence of a layered geometry are taken into account. Solutions can be obtained for both TM and TE polarizations and for near- and far-field regions. The numerical approach is described and the method is validated by comparison with examples given in the literature, with very good agreement. Results are presented for the scattering by a finite grid of three cylinders embedded in a slab.
Leaky‐wave antennas (LWAs) represent a class of radiators whose features can efficiently be described in terms of an electromagnetic traveling wave with complex wavenumber (leaky wave) able to propagate in guiding structures that do not completely confine the field. These guiding structures allow for a gradual loss of power to the external environment (leakage). In this article, in conjunction with the fundamental operating principles, the distinctive features of LWAs are described in terms of types and relevant radiation patterns. The basic analysis and the design techniques are summarized, and the main configurations are reviewed, emphasizing historical developments as well as new trends of such radiating elements.
Spatial self-imaging, consisting of the periodic replication of the optical transverse beam profile along the propagation direction, can be achieved in guided wave systems when all excited modes interfere in phase. We exploited material defects photoluminescence for directly visualizing self-imaging in a few-mode, nominal singlemode SMF-28 optical fiber. Visible luminescence was excited by intense femtosecond infrared pulses via multiphoton absorption processes. Our method permits us to determine the mode propagation constants and the cutoff wavelength of transverse fiber modes.
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