Diffraction by metallic planar gratings

Abstract

In this work, a kind of grating that, to our knowledge, has not yet been analyzed for diffractive purposes is proposed. The mentioned grating consists of metallic intercalated slits of two different metals on a glass substrate. The main characteristic and peculiarity of the proposed grating is that it is totally planar, without any slopes or grooves. We analyze the intensity distribution at the near- and far-field produced by the grating. The method used is rigorous-coupled wave analysis. We show how the metallic layer thickness is a crucial parameter to achieve the highest efficiency of the diffraction orders and, therefore, the highest contrast of the diffracted fringes. To conclude, we investigate how parameters such as the period, duty cycle, wavelength, or the used metals affect the diffracted field. Some nonexpected behaviors have been found. As we demonstrate by comparing with other kinds of gratings, the proposed grating would be useful in applications in which fringes are needed in both the front and back sides of the grating.