The Brewster reflectionless effect stands out as one of the simplest yet pivotal discoveries in manipulating waves. Initial investigations were limited to isotropic materials, but later, thanks to the advent of metamaterials, the phenomenon was found to expand into anisotropic materials.
An anomalous Brewster effect has recently been demonstrated in metamaterials, thus increasing the number of degrees of freedom. In materials without magnetic responses, the Brewster effect exclusively applies to transverse–magnetic (TM, or p–wave polarization) waves. Building on the equivalence between TM mode and 2D acoustics, the Brewster effect in acoustics with zero reflection has been demonstrated by utilizing acoustic metamaterials.
In their paper published in the journal Science Bulletin, the researchers first demonstrated this universal theory by matching the continuous boundary conditions and analyzing the relationship between the reflection coefficient and various parameters, proposing a precise method to confirm the near-zero reflection condition. Subsequently, they incorporated intrinsic losses into the permittivity tensors, illustrating a novel method to achieve asymmetric vortex transmission.
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