Scalar-Based Design of Binary Subwavelength Diffractive Lenses

Recent research1–9 has shown that if a binary-phase diffractive optical element (DOE) has features that are on the order of the illuminating wavelength, the performance limits set by scalar-based diffraction theory can be overcome. In fact, diffraction efficiencies in excess of 90% have been predicted for binary gratings that have subwavelength features.1,4,5 Due primarily to the availability of tools for modeling, the analysis and design of subwavelength DOEs (SWDOEs) has concentrated primarily on gratings.1-7,10 To overcome this limitation, we have developed numerical routines that use a boundary element method (BEM) to analyze diffraction from finite extent, aperiodic DOEs.11 In this paper we consider diffractive design, in particular, the design of diffractive lenses, subject to the constraints of fabrication.