Various designs and properties of quarter-wave stacks and their respective stopbands have been thoroughly investigated. Some design variations include high-order stacks, such as 2:1 or 3:1 stacks. In these cases, the ratio between the optical thickness of the low and high refractive-index layers is adjusted in integer multiples. Further investigation has evaluated detuned half-wave layer pairs. For detuned half-wave designs, the design of a specified quarter-wave stack can be adjusted to reduce the thickness of the high refractive-index layers while preserving the desired spectral performance. This chapter investigates methods to adjust or transform a quarter-wave stack (layer thickness) into a prespecified second quarter-wave stack with a different center wavelength (for the first-order stopbands). Spectral properties of two quarter-wave stacks can be produced by partially transforming one quarter-wave stack to generate high or partial reflectance at two wavelengths. This novel transform method has not been previously published.
For the proposed transform method, analytical (linear) equations are developed that can be used for any quarter-wave stack transform. Using these analytical equations, the partial transformation is investigated where properties of both stopbands are produced. Finally, the analytical determination of prespecified properties of both stopbands is evaluated.
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