A novel design algorithm based on a scanning search approach for designing a high-performance normal-incidence broadband visible or near infrared antireflection (AR) coating was proposed. The scanning search method consisting of scanning and elimination operations can be successively carried out to improve the AR performance and simplify the design structure; its design algorithm was straightforward and the resulting broadband AR performance was fairly good. It was shown that the average spectral reflectivities of the final designs in the visible region of 400 -750 nm and in the NIR region of 800 -1600 nm, obtained by the scanning search method of a two-material system, can be reduced below 0.042 and 0.085%, respectively.
Metamaterials that can be used in manipulating wave propagation have been shown in previous research. However, existing methods for controlling the propagation of shear waves remain a challenge. By combining the principle of wave destructive interference and the design concept of the gradient‐index phononic crystals, here new functionally graded phononic crystals with broadband gap for controlling shear wave propagation are presented. The proposed functionally graded phononic crystals are formed by an array of unit cells with different topological geometries, where the topological geometries of the unit cell are tailored to obtain the frequency bandgap guided by the wave destructive interference. Meanwhile, the frequency bandgap with a target width is obtained by combining the design concept of the gradient‐index phononic crystals. This work presents an approach to control the propagation of shear waves, and the advantages of the method reported in this work can be useful in engineering applications, such as bridges, railways, and buildings.
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