The metasurface is a nanodevice capable of manipulating the phase, polarization, and amplitude of incident light, and it can be applied in many optical devices. However, there is always a problem with metasurface devices: the fixed operating wavelength. An anisotropic gradient metasurface composed of periodic arrangement of differently sized tellurium posts resting on the sapphire substrate is proposed. The metasurface can exhibit efficient beam deflection under x- and y-polarized incidences, but the operating wavebands are different for the two polarizations. When the x-polarized light is normally incident, the diffraction efficiency remains higher than 95% within the wavelength region from 7140 to 7260 nm. The diffraction efficiency remains higher than 95% within the wavelength region from 7840 to 7940 nm under the y-polarized incidence. Furthermore, the proposed metasurface can act as a polarizer in the +1 diffraction order direction within the wavelength region from 6460 to 6760 nm. We hope that the proposed metasurface can play an important role in future free-space optical devices.
In this paper, we propose an anisotropic dual-band phase gradient metasurface in the infrared region based on tellurium material, which exhibits strong birefringence for z-cut. The refractive index of ordinary light no and extraordinary light ne are along the x- and y-direction of the metasurface, respectively. When a plane wave polarized along the x-direction is normally incident on the metasurface, the diffraction efficiency, which is defined as power of the deflected beam in the desired +1 diffraction order normalized to total transmission power, keeps higher than 95% within the wavelength from 7140nm to 7260nm, meanwhile the total transmission efficiency remains above 78%. On the other hand, the diffraction and total transmission efficiencies keep higher than 95% and 65% within wavelength range from 7840nm to 7940nm for the y-polarized illumination. The metasurface can be applied into polarization splitter, spectral beam splitter, and more in the future.
Printing technologies based on plasmonic structures have been intensively studied for their great advantages over organic colors and pigments. However, metallic nanoparticles have inherent plasmon damping and possess mainly electric-like resonances, thus there exists an urgent need for another degree of controlling the structural colors, for example the magnetic resonance modes. Here we propose truncated cone shaped silicon metasurfaces and numerically simulate their reflection characteristics. The designed metasurfaces are based mainly on magnetic Mie resonances because the strength of electric resonances is negligibly small compared with that of magnetic resonances. From numerical simulation, the intensity of the reflection peak reaches almost 90% and the full width at half-maximum (fwhm) of reflectance spectrum is 43nm. More detailed numerical analysis shows that distinct colors can be obtained giving a spatial resolution around 85000dpi. Specific colors with saturation close to 1 are available by selecting appropriate geometric dimension and period of the structure, which indicate the great application perspective of the proposed metasurfaces to produce well-defined colors covering the entire visible spectrum. The advantages of the designed metasurfaces are polarization-independence, cost-effective, stable, sustainable and CMOS(Complementary Metal Oxide Semiconductor)-compatible. Furthermore, the proposed structure works with a low aspect ratio of 0.46, which largely relieves the difficulty of process manufacturing.