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ISSN Imprimer: 0040-2508
ISSN En ligne: 1943-6009
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Polarization Transformation in Resonance Diffraction
RÉSUMÉ
In the scattering of electromagnetic radiation from a diffraction grating some variations occur both in the amplitude and the polarization of the specularly reflected component. These effects are quadratic in the amplitude of the grating z = a cos(gr) and, in general, are small for sloping gratings: a « d, where d = 2π/g is the grating period. However, in the case of resonance (|kt ± g| ≈ k, where kt is the tangential component of the wave vector of the incident wave, k = 2π/λ, and λ is the wavelength) where one or both first-order diffraction spectra graze along the grating, the rate of variations in the amplitude and polarization increases noticeably. This increase is caused by the fact that the grazing spectrum is in resonance with the natural mode of a well-conducting surface, i.e., with a surface electromagnetic wave; so this effect is of the same nature as the well-known Wood anomalies. Diffraction resonances underlie such phenomena as formation of surface structures [1], suppression of specular reflection [2], etc.
The resonance amplification of polarization transformation was experimentally observed in [3] and explained numerically by using cumbersome calculations in [4]. To study this phenomenon, in the present paper we employ an analytic approach based on the resonance theory of diffraction [5].