Modeling of a nanoscale rectangular hole in a real metal.

We propose and implement a simple and accurate method to analyze a subwavelength rectangular hole in a real metal and obtain the modal characteristics of its fundamental mode. Our results are found to be in excellent agreement with those reported in the literature, obtained by the effective index method (EIM) and finite-element and finite-difference methods. Unlike the EIM, the present method has no ambiguity in its implementation and is able to predict the major field components also, which may be useful in understanding the extraordinary transmission characteristics of such structures.