The electromagnetic theory should be applied to determine the diffraction efficiency of structures whose minimum line width is comparable with wavelength or the grooves are too deep, where scalar theory is no longer useful. The coordinate transformation method (the C method) is a very efficient method for obtaining continuous surface-relief grating efficiency for both TE and TM polarization. The local linear grating model (LLGM) models 2-D circular diffractive lens with combination of a series of local linear gratings. We synthesized and analyzed circular diffractive lens with a continuous profile not as previous authors who always use multi-lever structures. The result is compared with that of scalar theory and analysis using LLGM and rigorous coupled-wave theory. This optimization can be used as a complement of the scalar design of diffractive lens.
Ronchi gratings are widely used as beam splitters in interferometry. The phase Ronchi gratings are fabricated in K9 (or BK7) substrates using a photolithographic process and ion beam etching process. The geometry of the gratings was determined within the approximations of the scalar diffraction theory to minimize their diffraction intensities in 0 and 2 orders at 514.5nm. Their diffractive characteristics are measured using Ar+ laser at 514.5 and 496.5nm. The phase Ronchi gratings exhibit the diffraction intensity in 0 or 2 order to be three orders of magnitude less than that in 1 order.
Soft x-ray condenser zone plates are one of the most essential condensing and dispersing elements in the field of soft x-ray microscopy. The zone-plates are used at 3.2nm, whose diameters are 2.8mm. The widths of their outermost zone are 647nm. The zone plate is made of Au. Self-supporting zone plates are fabricated by holography-ion beam etching process to obtain x-ray lithography mask, the x-ray lithography, photolithography and micro electroplating process were used to obtain their self-supporting structure. The self-supporting zone plates are free of membrane absorption and degradation.