Axial propagation in nonhomogeneous dielectric material forms a canonical class of problems for which the Maxwell equations can be significantly simplified. Appropriate projection of the relative permittivity tensor reduces the curl relations to a set of four coupled ordinary differential equations, which can then be further reduced to a Helmholtz equation for the transverse components of the electric field phasor. Axial propagation through a chiral sculptured thin film (CSTF) layer is chosen as an example in which the reduced relations can be integrated exactly, while the Helmholtz equation can be solved approximately, using coupled-wave techniques. The electromagnetic response is thus shown to relate closely to Bragg grating physics, which is briefly reviewed. CSTFs are a burgeoning area of thin-film research lying somewhere between the topical fields of photonic materials and Bragg grating filters. The relationship to Bragg gratings evinces many potential application areas of CSTFs in optoelectronics research that exploit the circular polarization specificity of a CSTFs electromagnetic response. The examples reviewed here include narrow-band filtering, multi-pass filtering, and polarization routing.
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