Periodic crystals planar waves

The GOA has been widely used in the study of light propagation in photoelastic materials and liquid crystals. Recently, Ong and Meyer presented a general GOA formalism for wave propagation in optically inhomogeneous, planar, uniaxial media and found excellent agreement between the zeroth-order GOA and the exact solution for the case of a periodically bent nematic liquid crystal. The approach of Ong and Meyer, however, is restricted to linearly polarized light in planar structures. 

Fourier Model. High-resolulion image formation is considered most conveniently as occurring in two steps. In the first step, electrons propagate through the crystal and produce a two-dimensional periodic electron distribution at the exit face, which images the projected lattice potential or the projected electron density. In a second step, this exit face acts as a planar distribution of point sources of spherical electron waves, which interfere behind the foil and form the diffiacted beams that move in the lens sy.stem of the... 

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