Left-handed behavior of strontium-doped lanthanum manganite was revealed in the millimeter waveband. The bulk specimen of ${\text{La}}_{1-x}{\text{Sr}}_x{\text{MnO}}_3$ , was used as a boundary medium for one-dimensional photonic crystal. In the absence of magnetic field known Tamm peak appears in the forbidden zone of photonic crystal indicating that manganite is a single negative medium (negative permittivity). In the presence of external magnetic field somewhat above frequency of ferromagnetic resonance the additional (field sensitive) transparency peak appears in photonic crystal forbidden zone, indicating that manganite becomes double negative medium (negative permittivity and permeability). Model theoretical calculations corroborate the experimental findings.

Non-invasive blood glucose sensing is still actual scientific task for more safe and comfort diabetes care. This article shows correlation between blood optical properties and its glucose concentration. The transmission spectra of whole blood have been studied by the time-domain THz spectroscopy in the frequency range from 03 to 05 THz. Biosamples were produced from the same person with the diabetes mellitus during a short time period after the insulin injection have been used. Frequency dispersions of blood optical properties are obtained. Based on frequency dispersions, the dependences of blood glucose concentrations with the refractive index and permittivity are presented. This work is a part of the complex investigation, which focuses on the development of a non-invasive glucose measuring technique. Registering dependences between blood glucose level and blood optical parameters allows for using the reflective spectroscopy techniques in future for non-invasive blood glucose level sensing.

The complex dielectric constant of single-walled carbon nanotubes is tuned in the terahertz frequency range under light illumination.

In recent times, terahertz (THz) technologies have been actively applied in many biomedical research work, including gastric cancer diagnosis. In order to provide an effective removal of tumor during surgery, it is necessary to clearly distinguish it from different membranes of the stomach. In this work, we reported an investigation of various normal and cancer fresh gastric tissues using terahertz time-domain spectroscopy in the reflection mode. Refractive index and absorption coefficient of moderately differentiated and poorly differentiated gastric adenocarcinomas, as well as both serosa and mucosa were obtained in the frequency range from 0.2 to 1 THz. All cancer tissues were distinguishable from normal ones. The influence of the morphology of the investigated tissues on the obtained optical properties is discussed. The obtained results demonstrated a potential of THz time-domain spectroscopy to discriminate a tumor from normal serous and mucous gastric membranes. Thus, this method might be applied to gastric cancer diagnosis.

In this paper, we show the ability of usage intercalated few-layer graphene for the development of an optically tunable absorbing metasurface. The geometrical parameters of the metasurface are optimized using the equivalent circuit model theory. Depending on the geometrical parameters, the metasurface shows frequency or absorption level tunability: the first design allows us to achieve the modulation of absorption up to 35%, while the second one shows absorption maximum frequency modulation of δν = 0.15 THz. The analytical results are proven by numerical simulations and explained by the interference theory. The suggested metasurface enables us to achieve an optically controllable absorption for a wide range of applications in terahertz imaging, selective absorption, and photo-detection.

The tunable terahertz (THz) Fano-resonant filter based on hybrid metal-graphene metamaterial was proposed. The optical parameters of metasurface with unit cell in the form of a cross-shaped graphene sheet in the center of a square gold ring were simulated by the finite element method using a surface conductivity model of a graphene monolayer. The narrowband modulation of the transmission by varying the Fermi level of the graphene and the position of graphene cross inside the metal ring was demonstrated. Simulation results were well explained theoretically using a three-coupled oscillator model. The proposed device can be used as a narrowband filter in wireless THz communication systems and sensing applications.