Abstract
We introduce chiral gradient metasurfaces that allow perfect transmission of all the incident wave into a desired direction and simultaneous perfect rotation of the polarization of the refracted wave with respect to the incident one. Besides using gradient polarization densities which provide bending of the refracted wave with respect to the incident one, using metasurface inclusions that are chiral allows the polarization of the refracted wave to be rotated. We suggest a possible realization of the proposed device by discretizing the required equivalent surface polarization densities realized by proper helical inclusions at each discretization point. By only using a single optically thin layer of chiral inclusions, we are able to unprecedentedly deflect a normal incident plane wave to a refracted plane wave at $45^{\circ}$ with $72\%$ power efficiency which is accompanied by a $90^{\circ}$ polarization rotation. The proposed concepts and design method may find practical applications in polarization rotation devices at microwaves as well as in optics, especially when the incident power is required to be deflected.
Highlights
From the beginning of the 21st century, the investigation of metasurfaces, i.e., optically thin layers of arrayed subwavelength inclusions, to shape the wavefront of the electromagnetic waves at will is dramatically increased compared to that of bulky metamaterials [1–25]
By applying the so-called generalized laws of reflection and refraction, designed phase gradient metasurfaces achieved about 25% of transmitted power for manipulation of transmitted waves [26, 27]
The performance of this metasurface design is compared with the ideal case, and a power transmission efficiency of 72% is achieved for a 90° polarization rotation and a 45° wavefront deflection which is much higher than 25% efficiency reported in the literature for a smaller angle of wavefront deflection (e.g., 30°) using the so-called generalized laws of reflection and refraction
Summary
From the beginning of the 21st century, the investigation of metasurfaces, i.e., optically thin layers of arrayed subwavelength inclusions, to shape the wavefront of the electromagnetic waves at will is dramatically increased compared to that of bulky metamaterials [1–25]. By applying the so-called generalized laws of reflection and refraction, designed phase gradient metasurfaces achieved about 25% of transmitted power for manipulation of transmitted waves [26, 27]. Each unit cell consists of four interlaced helices which fulfills the desired polarization densities, when judiciously engineered The performance of this metasurface design is compared with the ideal case, and a power transmission efficiency of 72% is achieved for a 90° polarization rotation and a 45° wavefront deflection which is much higher than 25% efficiency reported in the literature for a smaller angle of wavefront deflection (e.g., 30°) using the so-called generalized laws of reflection and refraction Our proposal has the advantage of perfect performance (refraction and polarization rotation) when compared to these devices
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