| High-efficiency finite-aperture diffractive optical elements with features on the order of or smaller than the wavelength of the incident illumination have been designed. The focus is on the use of a modified scalar-based iterative design method that incorporates the angular spectrum approach. Upon comparison with rigorous electromagnetic analysis techniques (such as the boundary element method and finite difference time domain analysis), it was found that the scalar-based design method was valid for a surprisingly large parameter space, including sub-wavelength features.; Specifically, two-dimensional 1-2 beamfanner designs explored the limits of scalar diffraction theory for finite aperture diffractive optical elements (DOEs) with sub-wavelength minimum feature sizes that operate in the near field. In using scalar diffraction theory, it is assumed that a DOE profile is described by a transmission function, and the field just past the DOE was propagated to a particular plane of interest using the angular spectrum approach. With appropriate choices of weighting functions used in an iterative angular spectrum algorithm (IASA), devices were accurately designed with sub-wavelength features to operate in the near-field. The scalar-based results were compared with those from rigorous electromagnetic analysis techniques such as the finite-difference time-domain method (FDTD) and the boundary element method (BEM). The scalar results agreed almost identically with rigorous analyses even for wide angular spreads of the desired field pattern in the plane of interest.; Also presented in this dissertation is the design of a diffuser for use in an autostereoscopic display system. The feature sizes of the device were of the same order of magnitude as the incident wavelength. The device was designed using an Iterative Fresnel Transform Algorithm (IFTA) and the results were compared with those obtained via rigorous analysis. |
