Recent decades metamaterials in terahertz frequencies become very popular in the scientific society. Metamaterials is an arrangement of artificial structural elements (unit cell) that gives properties which cannot be found in nature. The effective properties of metamaterials depend on their design. This fact provides a big variety in applications of metamaterials as filters, absorbers, polarizers, etc.
In this work we have studied the influence of the chiral metasurface resonator conductivity on polarizing properties of the metasurface. The unit cell of the metasurface consists of metallic gammadion crosses on both sides of the dielectric substrate. The petals of the upper resonators were partly made of different metals. Each combination of metals in design of the resonator leads to a difference in transmission of the metasurface. Due to chirality, transmission coefficients for left- and right-handed polarized waves are different. This phenomenon causes changes in the polarization ellipse of transmitted wave. The metasurface was numerically simulated using CST Microwave Studio by finite-elements method in frequency domain. The virtual experiment shows a difference in ellipticity and azimuth polarization rotation angle spectra of resonators with different conductivity. These results provide usage of materials with changeable conductivity, for example, graphene, in development of tunable polarization converter.
The investigated metasurface might be used in terahertz polarimetry of cancer, teeth and skin deceases. These measurements can be performed by terahertz time-domain spectroscopy.
|