This work is devoted to investigation of optical properties (dispersion of refractive index, permittivity and absorption coefficient) of human nails in THz frequency range. These data were obtained by THz time-domain spectroscopy (TDS) technique in transmission mode. These results may be used to develop non-invasive technique of human pathologies control using nail as reference sample in reflection mode of THz TDS.
We revealed that after exposure of scarified cornea of rabbits to low-intensity pulsed terahertz radiation 0.1 to 1.8 THz a positive effect on epithelization triggered within the first hours was higher compared to non-irradiated cornea. However, while elevating power of terahertz radiation up to 60.8 nW it resulted in retarding epithelialization process. At that, irradiation did not affect timeframe of complete corneal epithelialization. During experiments it was found that terahertz radiation was well tolerated, exhibited no toxic and allergic reactions or resulted in pathohistological changes in the eye tissues. Also, low-intensity terahertz radiation did not affect normal physiological functions of the eyes and facilitated to re-epithelialization of scarified eyes in rabbits.
In this paper we study the influence of the period between U-shaped split-ring resonators (SRRs) on the trans- mission/absorbtion properties and refraction index of metasurfaces in THz frequency range (0.1 - 1 THz) using experiments and numerical simulations. The metasurfaces are formed by U-shaped SRRs arrays. The period varies from 63 to 300 μm The metasurface electromagnetic responses are obtained using terahertz time-domain spectroscopy. The experimental and numerical results reveal the shift in transmission spectra for the metasurface response and the tuning of absorbtion intensity at the period between U-shaped SRRs changing. The notable change in the metasurface refractive index is shown.
The ideas of employing the unique properties of metamaterials for cloaking and invisibility applications has been
recently suggested and investigated by several groups, because they may find numerous applications in physics and
technology. While many of the recent designs of the cloaking structures are based on the transformation optics and exact
formulas, the original concept suggested by Tretyakov employed the periodical set of parallel-plate waveguides with the
height smoothly varying from H to h in order to reduce drastically the total scattering cross-section of a given object and
to obtain broadband cloaking effect. Our paper is devoted to improvement of this design to make tunability and nonlinear
effect. The Tretyakov’s design was scaled for Ku-band frequencies and the cloak was placed into rectangular waveguide.
The broad transmission band (“invisibility region”) was obtained. The tunability of transmission band was realized by
addition the capacitors into the cloak, between metallic plates. The cloaking system was simulated numerically by CST
Microwave Studio. The possibility of invisibility switching on/off was shown by changing of capacity of varactor diodes
from 0.4 to 3.4 pF by incident power. The nonlinear cloak behavior was shown at microwaves.