Bianisotropic Metasurfaces Research Articles

Revisiting substrate-induced bianisotropy in metasurfaces

Recently, it has been shown that a metasurface of plasmonic nanospheres deposited on a highly refractive substrate requires a bianisotropic magnetoelectric coupling for its effective description. The effect has been coined substrate-induced bianisotropy. It leads to an asymmetric reflectance similar to bianisotropic metasurfaces. In this work, through a circuit model, we show that such bianisotropy does not necessarily emerge for all substrated metasurfaces. Indeed, we show that the thickness of the metasurface plays a crucial role to encounter substrate-induced bianisotropy. Moreover, by taking advantage of substrate-induced bianisotropy, we present the necessary conditions for the circuit model parameters to compensate the asymmetric reflectance generated by an intrinsically bianisotropic metasurface. We finally express that, in substrated metasurfaces, the asymmetric reflectance and the bianisotropic response are two separate issues albeit with interdependencies.

Bianisotropic Metasurfaces for Optimal Polarization Control: Analysis and Synthesis

Two-dimensional metamaterials (metasurfaces) are desirable for their ability to modify electromagnetic fields--for example, producing perfect absorbers for stealth technologies. Metasurfaces reported to date, however, have demonstrated only limited control over the polarization and phase of these fields. In this work, the authors incorporate metamaterial anisotropy and chirality into calculations to derive simple, general, closed-form expressions relating constituent parameters of an arbitrary bianisotropic metasurface to its reflection and transmission behaviors.

High performance bianisotropic metasurfaces: asymmetric transmission of light.

It is experimentally shown that bianisotropic metasurfaces allow for extreme polarization control of light with high performance. A metasurface providing asymmetric transmission (i.e., polarization conversion) of circularly polarized light is reported at a wavelength of 1.5 μm. The experimental transmittance and extinction ratio are 50% and 20:1, which represents an order of magnitude improvement over previous optical structures exhibiting asymmetric transmission. The metasurface consists of patterned gold sheets that are spaced at a subwavelength distance from each other. The same design and fabrication processes can be used in the future to completely control the phase, amplitude, and polarization of light.