The impact of optical radiation of femtosecond duration on human glial cells

The paper presents the results of the studies of influence of optical radiation with wavelengths of 520 and 780 nm on human glial cells (U251) at the range of exposure times ∼ 1-15 min. It was found that after the first minute of irradiation at the wavelength of 780 nm, the relative number of apoptotic cells significantly increased. The result corroborates the concept of biological hazard of optical radiation for tumor cells, and suggests that the approach has a great potential in clinical application for the treatment of human glioma

Multi-layered graphene based optically tunable terahertz absorber

Abstract We present a broadband tunable terahertz (THz) absorber, which consists of cross-shaped multi-layered graphene (MLG) resonators. The proposed absorber possesses almost perfect absorption over the range 0.4—0.8 THz and can be easily fabricated. Dynamical tuning of absorption band is achieved by external optical pumping of modest intensity. This multi-layered graphene-based absorber has high potential for various THz applications

Effect of Antimony Buffer Layer on the Electric and Magnetic Properties of 200 and 600 nm Thick Bismuth Films on Mica Substrate

We report on the production of 200 and 600 nm thick Bi films on mica substrate with 10 nm thick Sb sublayer between Bi and mica. Two types of films have been studied: block and single crystal. Films were obtained using the thermal evaporation technique using continuous and discrete spraying. Discrete spraying allows smaller film blocks size: 2–6 μ m compared to 10–30 μ m, obtained by the continuous spraying. Single crystal films were made by the zone recrystallization method. Microscopic examination of Bi films with and without Sb sublayer did not reveal an essential distinction in crystal structure. A galvanomagnetic study shows that Sb sublayer results in the change of Bi films properties. Sb sublayer results in the increase of specific resistivity of block films and has no significant impact on single crystal films. For single-crystal films with Sb sublayer with a thickness of 200 nm the Hall coefficient has value 1.5 times higher than for the 600 nm thickness films at 77 K. The change of the Hall coefficient points to change of the contribution of carriers in the conductivity. This fact indicates a change in the energy band structure of the thin Bi film. The most significant impact of the Sb sublayer is on the magnetoresistance of single-crystal films at low temperatures. The increase of magnetoresistance points to the increase of mobility of the charge carriers. In case of detecting and sensing applications the increased carriers mobility can result in a faster device response time

Optical activity of graphene-based chiral metasurface in THz frequency range

Abstract In this paper the optical activity of two types of graphene-based chiral metasurfaces with two different variations of graphene inclusion positions was studied. The gammadion resonators of the unit cell were partly made of graphene. Three resonant frequencies of the metasurfaces in the frequency range of 0.1—0.5 THz were found. It is shown that the value of optical activity expressed in azimuth polarization rotation angle strongly depends on the chemical potential of graphene petals, as well as on the position of graphene inclusions

Graphene-based optically tunable structure for terahertz polarization control

Abstract We present a theoretical model of optically tunable graphene-based structure for polarization characteristics control of transmitted terahertz (THz) wave. The experimental verification was performed using a THz time-domain polarimetry setup. The tunability is achieved by applying an external optical pumping and magnetic field. The structure shows the possibility for dynamical control of ellipticity and azimuth angles of polarization state of THz radiation in a transmission mode. This study indicates a strong potential for using graphene-based structures for polarization sensitive applications such as THz wireless communications and biomedical research

Terahertz-to-infrared converters for imaging the human skin cancer:challenges and feasibility

Abstract Purpose: Terahertz (THz) medical imaging is a promising noninvasive technique for monitoring the skin’s conditions, early detection of the human skin cancer, and recovery from burns and wounds. It can be applied for visualization of the healing process directly through clinical dressings and restorative ointments, minimizing the frequency of dressing changes. The THz imaging technique is cost effective, as compared to the magnetic resonance method. Our aim was to develop an approach capable of providing better image resolution than the commercially available THz imaging cameras. Approach: The terahertz-to-infrared (THz-to-IR) converters can visualize the human skin cancer by converting the latter’s specific contrast patterns recognizable in THz radiation range into IR patterns, detectable by a standard IR imaging camera. At the core of suggested THz-to-IR converters are flat matrices transparent both in the THz range to be visualized and in the operating range of the IR camera, these matrices contain embedded metal nanoparticles (NPs), which, when irradiated with THz rays, convert the energy of THz photons into heat and become nanosources of IR radiation detectable by an IR camera. Results: The ways of creating the simplest converter, as well as a more complex converter with wider capabilities, are considered. The first converter is a gelatin matrix with gold 8.5-nm diameter NPs, and the second is a polystyrene matrix with 2-nm diameter NPs from copper–nickel MONEL® alloy 404. Conclusions: An approach with a THz-to-IR converter equipped with an IR camera is promising in that it could provide a better image of oncological pathology than the commercially available THz imaging cameras do

Characterization of silver nanowire layers in the terahertz frequency range

Funding Information: Funding: The work was supported by the European Union’s Horizon 2020 FET Open project TERAmeasure (grant agreement No 862788), by the “International Research Agendas” program of the Foundation for Polish Science co-financed by the European Union under the European Regional Development Fund (No. MAB/2018/9), by the statutory sources of the Department of Structural Materials, Military University of Technology (project no. UGB 22–846/2021/WAT) and by the Ministry of Science and Higher Education of the Russian Federation (project no. FSRR-2020-0004), (Igor S. Nefedov). A. Krajewska was supported by the Foundation for Polish Science (FNP). Publisher Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland.Thin layers of silver nanowires are commonly studied for transparent electronics. However, reports of their terahertz (THz) properties are scarce. Here, we present the electrical and optical properties of thin silver nanowire layers with increasing densities at THz frequencies. We demonstrate that the absorbance, transmittance and reflectance of the metal nanowire layers in the frequency range of 0.2 THz to 1.3 THz is non-monotonic and depends on the nanowire dimensions and filling factor. We also present and validate a theoretical approach describing well the experimental results and allowing the fitting of the THz response of the nanowire layers by a Drude–Smith model of conductivity. Our results pave the way toward the application of silver nanowires as a prospective material for transparent and conductive coatings, and printable antennas operating in the terahertz range—significant for future wireless communication devices.Peer reviewe