A novel technique is proposed to calculate the field due to an arbitrary impressed source of finite extent in proximity with an infinite periodic structure such as an artificial material. The algorithm is based on a spectral domain finite-difference time-domain (FDTD) method combined with the array scanning method (ASM). Using this approach, only a single periodic cell of the periodic structure needs to be numerically modeled. Examples are used to demonstrate the accuracy and efficiency of the proposed approach. © 2007 IEEE.

We present here an algorithm to evaluate the field in the near zone produced by a finite-size electromagnetic source in a periodic structure, referred to as the array scanning method (ASM) - FDTD method. Using a frequency-dependent silver permittivity model, obtained from measurement at optical and infrared frequencies, we implemented the corresponding modeling equations in the ASM-FDTD algorithm using the Z-transform technique. The developed algorithm is applied to the study of the enhanced radiation of a magnetic line source in a corrugated silver film, and the results indicate that the enhancement is due to the excitation of a leaky mode. We also show that other waves may be excited by the source depending on its location, and how this affects the radiation pattern.