The behavior of quasi-periodic and nonperiodic (chirp) Bragg structures with thin lossy layers is considered. In order to calculate the dependence of the reflection coefficient against frequency, transmission matrix method is used. A deep minimum of reflection coefficient for any frequency is implemented by properly choosing the thickness of the last thin film and its optical distance to the substrate. The possibility of providing broadband reflection by nonperiodic structures is offered.

d-3-up

Frequency and angular dependences of Reflection (logarithm scale) coefficient for quasi-periodic Bragg structures with thin lossy layers

d-3-down

Frequency and angular dependences of Reflection (linear scale) coefficient for quasi-periodic Bragg structures with thin lossy layers

Quasi-periodic Bragg structures with thin lossy layers can operate as good absorbers in a given frequency band. Variation of the conductivity of a lump inhomogeneity is obtained by varying the thickness of a thin lossy layer. For a fixed frequency, minimum reflectivity can be provided by the choice of the parameters of layer thickness and the distance to the substrate. Broadband absorption is achieved by nonuniform perturbation of optical thickness of the separating dielectric layer.

Languages: Matlab

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“FORTRAN is not a flower but a weed — it is hardy, occasionally blooms, and grows in every computer.”

Alan J. Perlis