Many functions could be employed to create unique patterns of layer thickness in discrete, multilayer thin-film coatings and the corresponding spectral performance. Discrete, layered quarter-wave stacks are routinely used for their stopband properties at harmonics of the center wavelength of the first-order stopband. An inhomogeneous rugate design produces a stopband by sinusoidal modulation of the continuously varying refractive index. This chapter investigates the sinusoidal modulation of the optical thickness of discrete, homogeneous layers in a quarter-wave stack, as well as the synthesis of these thickness-modulated designs with a rugate-equivalent design.
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