In this study, three-component 1-D photonic crystal (PC) structures were investigated by modeling them as two-component PCs with an additional regular layer. The gap map (GM) approach and the transfer matrix method (TMM) were used in order to mathematically describe these structures. The introduction of a third component to a 1-D PC allows manipulation of the optical contrast to a high degree of precision by varying the thickness and refractive index of the additional layer. The introduction of a third component to the 1-D PC partially reduces the area of the photonic stopbands (SBs) on the GM, leaving the rest of SB area unchanged from that in the GM for the original, two-component, PC. Using this approach to decrease optical contrast in PCs, omnidirectional bands (ODBs) can be obtained in high-contrast periodic structures constructed from, for example, an array of silicon and air. Several mathematical models of three-component 1-D PCs are discussed, some of which may have practical applications.
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