Electromagnetic Analysis of Axially-Symmetric DOEs Using the FDTD Method

Many useful diffractive optical elements (DOEs) contain axial symmetry, e.g. lenses and mode shaping elements. Typically these structures are analyzed using scalar-based diffraction methods. However, when the profile of the DOE has variations on a scale comparable to the illumination wavelength scalar theory is not valid. In these cases a rigorous solution to the electromagnetic boundary value problem must be obtained. Unfortunately, most techniques for the rigorous analysis of such DOEs are only applicable to two-dimensional or periodic profiles. An exception to this is our method of moments (MOM) paper included in the technical digest of this conference. Although we have demonstrated the MOM to be a viable method for the analysis of axially-symmetric DOEs, in this paper we present an alternative technique based on the finite-difference time-domain (FDTD) method that is computationally more efficient and has broader application.