Abstract

When a light field interacts with structures that have complex geometric features comparable in size to the wavelength of the light, it is not permissible to invoke the assumptions of the classical diffraction theory, which simplify the problem and allow for approximate solutions. For such cases, direct numerical solutions of the governing equations are sought through approximating the continuous time and space derivatives by the appropriate difference operators. The Finite Difference Time Domain (FDTD) method discretizes Maxwell’s equations by using a central difference operator in both the time and space variables.¹ The electric and magnetic fields are then represented by their discrete values on the spatial grid, and are advanced in time in steps of ∆t. The numerical solution thus obtained to Maxwell’s equations (in conjunction with the relevant constitutive relations) provides a highly reliable representation of the electromagnetic field distribution in the space-time region under consideration. This paper presents examples of application of the FDTD method to problems of interest in optical data storage, namely, those that involve the interaction between a focused beam of light and subwavelength structures such as small pits and apertures in a thin film supported by a transparent substrate.

© 2003 Optical Society of America