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In the present paper we demonstrate and compare different properties of Bi and Bi1-xSbxthin films placed on polyimide (PI) substrate in frequency range from 0.2 to 1.0 THz. Bi films with a thickness of 40, 105 and 150 nm have been studied as well as 150 nm Bi1-xSbxsolid solutions with Sb concentration of 5, 8, 12 and 15 %. An effective refractive index and permittivity of whole substrate/film structures have been derived by using terahertz time-domain spectroscopy (THz-TDS) method. These measurements have shown the positive phase shift in PI substrate with a thickness of 42 μm and revealed that it is barely transparent in studied frequency range, but the whole substrate/film structure provides the negative phase shift of terahertz wave. It was shown that the permittivity depends on mobility of charge carriers which is driven by film thickness and antimony content.

Terahertz time-domain spectroscopic polarimetry (THz-TDSP) method was used to study of polarization properties of a randomly oriented single-walled carbon nanotube (SWCNT) thin film on a high resistivity monocrystalline silicon (Si) substrate in terahertz (THz) frequency range under an external optical pumping and an external static magnetic field. Frequency dependencies of azimuth and ellipticity angles of a polarization ellipse and the polarization ellipse at various frequencies of the electromagnetic waves transmitted through the Si substrate and the SWCNT on the Si substrate were obtained experimentally based on the solution of the system of the Stokes parameters. The results of the study of this magneto-optically tunable structure confirm the fact that, based on the Faraday effect in the SWCNT, it is possible to devise efficient tunable THz polarization modulators for use in physics, chemistry, medicine, and the latest security and telecommunication systems.

Due to the rapid development of THz photonics, it became necessary to create detectors of THz radiation, which would simultaneously be high-sensitive, high-speed and work at room temperature. We demonstrate that the use of thermoelectric thin Bi-Sb films with high sensitivity to THz radiation may solve this problem. The films synthesized by means of thermal evaporation in vacuum were affected by terahertz radiation at the frequency of 0.14 THz. The temporal dependencies of a voltage drop and temperature difference were measured. The experimental results prove the possibility for the use of Bi-Sb films in THz radiation detection at room temperature.

We present the study of the influence of different thin silver nanowire layers on electrical and optical properties in the Terahertz (THz) frequency range. We demonstrate that the absorbance, transmittance and reflectance of the metal nanowire layers in the frequency range of 0.2~THz to 1.2~THz is non-monotonic and depends on the nanowire dimensions and density. We present and validate also a theoretical approach describing well the experimental results and allowing to model the THz response as function the nanowire layer structure. Our results pave the way toward the application of silver nanowires as a perspective material for transparent and conductive coatings, and printable antennas operating in the terahertz range – significant for future wireless communication devices.

Magneto-optic Faraday effect in unaligned single-wall carbon nanotube thin films with different geometric parameters on transparent float glass substrates was experimental studied in a frequency range 0:2–0:8 THz (corresponding to a range from ~1:50mm to ~0:37mm) at a controlled room temperature of 291–293K, and a relative humidity of 40–45%. A change of 15° in an azimuth angle, and of 10° in an ellipticity angle was achieved. The results show that by using carbon nanomaterials-based structures it is possible to devise efficient tunable polarizers that can be used in the advanced areas of terahertz nanophotonics.

Now, terahertz (THz) technologies have been actively studied and applied in various biomedical applications including cancer diagnosis. It is related with unique features of THz spectroscopy, such as high sensitivity to water and other polar molecules, the presence of resonant peaks of various biomolecules in the THz frequency range, harmless of THz radiation to biological tissues. In this work, we have investigated different types of gastric tissues using THz spectroscopy and obtain refractive indices in the frequency range from 0.2 to 1 THz. Fourier transform infrared spectroscopy (FT-IR) was also applied in order to see what’s components of tissues make the most significant contribution in optical response and, therefore, allow to discriminate cancer.

Petroleum products are the largest source of energy in the world, accounting for over 30% [1]. The amount of oil production increases annually, as does the production of petroleum products. In 2015, 4181 million tons of petroleum products were manufactured, and in 2018, 4350 million tons were produced [2]. It becomes necessary to analyze oil and oil products to determine their quality. The traditional chemical method for analyzing crude oil and petroleum products requires a large number of instruments, as well as a lot of time and consumables [3-5]. To speed up the process of determining the quality of oil products, it is possible to perform spectral analysis using terahertz time-domain spectroscopy. The optical properties obtained using terahertz spectroscopy in the time domain of a petroleum product can be used to analyze its quality. At the moment, there are studies of crude oil for the presence of asphaltenes and their effect on the optical properties of crude oil [6]. The absorption coefficient spectrum of crude oil shows moderate absorption due to asphaltene with no clear indications, except for some narrow absorption lines, which are caused by water molecules adsorbed on the asphaltene. Other research focuses on petroleum products, namely oils, gasoline and diesel [7]. As a result, oils have a high absorption coefficient at high frequencies, the same results were observed for gasoline and diesel fuel. This work is devoted to the spectral analysis of a mixture of gasoline with an octane rating of 98 and diesel fuel, depending on the concentration of gasoline, using terahertz time-domain spectroscopy.

Magneto-optic Faraday effect in unaligned single-wall carbon nanotube thin films with different geometric parameters on transparent float glass substrates was experimental studied in a frequency range 0:2–0:8 THz (corresponding to a range from ~1:50mm to ~0:37mm) at a controlled room temperature of 291–293K, and a relative humidity of 40–45%. A change of 15° in an azimuth angle, and of 10° in an ellipticity angle was achieved. The results show that by using carbon nanomaterials-based structures it is possible to devise efficient tunable polarizers that can be used in the advanced areas of terahertz nanophotonics.

At present, due to the rapid development of THz technology in medical applications, it becomes urgent to develop stable test objects (phantoms) for calibration, optimization of the operation of devices, and verification of the research methods used. In this work, a five-component phantom has been developed based on water, glycerin, starch, bentonite, and gelatin, and it was shown that these phantoms can be used as indicators of the level of dehydration of the renal tumor tissue. The mechanical properties of the phantom were investigated, the dispersions of the refractive index and absorption coefficient of the biocomposite were determined in the range from 0.2 to 1 THz. To simulate the optical parameters of a phantom depending on the concentration of inclusions, an iterative method was developed and it was found that this method makes it possible to simulate the optical parameters of a phantom at low concentrations of bentonite. It is shown that in the structure of a five-component phantom, during fabrication, clusters of starch particles are formed, and the resonant interaction of the incident THz radiation with cluster particles leads to the excitation of whispering gallery modes.

Magneto-optic Faraday effect in unaligned single-wall carbon nanotube thin films with different geometric parameters was experimental studied in a frequency range 0.2–0.8 THz at a controlled room temperature of 291–293 K, and a relative humidity of 40–45%. A change of 15° in an azimuth angle, and of 10° in an ellipticity angle was achieved.

Significance: A new concept of a biotissue phantom for terahertz (THz) biomedical applications is needed for reliable and long-term usage. Aim: We aimed to develop a new type of biotissue phantom without water content and with controllable THz optical properties by applying graphite powders into a polyvinyl chloride plastisol (PVCP) matrix and to give a numerical description to the THz optical properties of the phantoms using the Bruggeman model (BM) of the effective medium theory (EMT). Approach: The THz optical properties of graphite and the PVCP matrix were measured using THz time-domain spectroscopy, which works in the frequency range from 0.1 to 1 THz. Two phantoms with 10% and 12.5% graphite were fabricated to evaluate the feasibility of describing phantoms using the EMT. The EMT then was used to determine the concentration of graphite required to mimic the THz optical properties of human cancerous and healthy oral tissue. Results: The phantom with 16.7% of graphite has the similar THz optical properties as human cancerous oral tissue in the frequency range of 0.2 to 0.7 THz. The THz optical properties of the phantom with 21.9% of graphite are close to those of human healthy oral tissue in the bandwidth from 0.6 to 0.8 THz. Both the refractive index and absorption coefficient of the samples increase with an increase of graphite concentration. The BM of the EMT was used as the numerical model to describe the THz optical properties of the phantoms. The relative error of the BM for the refractive index estimation and the absorption coefficient is up to 4% and 8%, respectively. Conclusions: A water-free biotissue phantom that mimics the THz optical properties of human cancerous oral tissue was developed. With 21.9% of graphite, the phantom also mimics human healthy oral tissue in a narrow frequency range. The BM proved to be a suitable numerical model of the phantom.

Terahertz time-domain spectroscopic polarimetry (THz-TDSP) method was used to experimental study polarization properties of unaligned single-wall carbon nanotube thin films with different geometric parameters on transparent float glass substrates in a frequency range 0.2-0.8 THz at a controlled room temperature of 291–293K, and a relative humidity of 40–45%. Frequency dependences of azimuth and ellipticity angles of a polarization ellipse of electromagnetic waves transmitted through the samples were obtained for values of 0.2–1:.0Wcm-2 of an external 980nm near infrared optical pumping, with an external static magnetic field of ~0:3T. A change of 15° in the azimuth angle, and of 10° in the ellipticity angle was achieved. The results show that by using carbon nanomaterials-based structures it is possible to devise efficient and affordable magneto-optically tunable polarization modulators that can be used in the advanced areas of terahertz nanoscience and nanotechnologies.

With the fast development of terahertz technology in medical diagnosis and monitoring, it has become important to investigate the application of THz radiation in the cancer treatment assessment during the therapy. In this paper, a buccal drug delivery system is studied as the first step towards this application. The drug delivery system is based on a gelatin-starch biopolymer matrix filled with plasticizing glycerol and various contents of reinforcing particles of bentonite clay. The biopolymers were subjected to morphology analysis using optical microscopy, analysis of mechanical tensile properties, and analysis of terahertz optical properties, followed by a theoretical approach of the experiment. The results show a visible effect of the bentonite content on both of the mechanical and terahertz optical properties of the biopolymer. These findings allow us to confirm the feasibility of using THz radiation for cancer assessment during therapies. The proposed biopolymer also has the potential to be applied as a substrate when carrying out in-vivo optical property measurement of biotissue in terahertz frequency range.

We report results of galvanomagnetic and terahertz time-domain spectroscopy measurements on thin films of Bi 1 &minus, x Sb x on polyimide and mica substrates with various antimony concentrations (x from 0 to 15 %) and film thickness (70, 150 nm). The resistivity, Hall coefficient and magnetoresistivity of the films were measured experimentally in the magnetic field of 0.65 T at room temperature. Mobility and concentration of electrons and holes in the film plane were calculated using the transport coefficients. The terahertz time-domain spectroscopy is used to measure the complex conductivity and permittivity of Bi 1 &minus, x Sb x thin films on the dielectric substrates in the frequency range from 0.2 to 1 THz. The plasma frequency, relaxation time, DC conductivity and effective carrier mass were extracted from these data and evaluated as functions of the Sb concentration for different film thickness and substrate. We observed that the film magnetoresistivity decreases with increasing the Sb concentration and for most of the films the Hall coefficient is negative and depends on the external factors insignificantly. We show that the mobility of charge carriers weakly depends on Sb concentration, which confirms the assertion about the scattering of carriers on themselves and not on defects in the structure. It was revealed that film static and dynamic resistivity (conductivity) as well as dielectric permittivity depend on Sb content and the film thickness. The results may be used for development of various thermoelectric, electronic and optical devices, such as THz detectors or components which can control the properties of THz radiation.

A terahertz (THz) detector based on thermoelectric thin films was simulated using the finite elements method. The thermoelectric circuit consisted of S b and B i 88 S b 12 150-nm films on the mica substrate. S b , B i 88 S b 12 , and mica-substrate properties have been measured experimentally in the THz frequency range. The model of electromagnetic heating was used in order to estimate possible heating of S b - B i 88 S b 12 contact. THz radiation power varied from 1 &mu, W to 50 mW, and frequency varied in the range from 0.3 to 0.5 THz. The calculations showed a temperature difference of up to 1 K, voltage up to 0.1 mV, and responsivity of several mVW - 1 . The results show that thin S b and B i - S b thermoelectric films can be used for THz radiation detection at room temperatures.

Subject of Research.The paper presents the study of blood biochemical composition (bilirubin, creatinine, triglycerides, uric acid) effect on its optical properties, refractive index and absorption coefficient, in terahertz frequency range. Method. To obtain the values of the refractive index and the absorption coefficient, the method of terahertz time-domain spectroscopy was used in the transmission mode. Concentrations of total bilirubin, creatinine and triglycerides were measured in blood serum by the colorimetric method, the pseudokinetic method and the enzymatic method, respectively. The glucose level was determined in blood plasma by the enzyme method. All measurements of blood component concentrations were carried out at the Almazov National Medical Research Centre. Main Results. The optical properties of blood with various biochemical composition were obtained using terahertz time-domain spectroscopy at the frequency of 0.4THz. It is shown that the refractive indices and the absorption coefficients of blood decrease with an increase in the concentration of bilirubin and creatinine. It has also been found that with an increase in the concentration of uric acid and triglycerides, the refractive index of blood increases and the absorption coefficient of blood decreases, respectively. The correlation between the refractive index and the concentration of triglycerides and the correlation between the blood absorption coefficient and the concentration of uric acid were not revealed. Practical Relevance. The observed correlations between the concentrations of blood components and the optical properties are useful in the development of a new technique for blood analysis.

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.

10.1063/5.0062228.1A room-temperature terahertz (THz) detector based on a thermoelectric frequency selective surface (FSS) has been numerically simulated, designed, fabricated, and tested. The FSS has been fabricated from a 150 nm thin Bi88Sb12 thermoelectric film with the engraved periodic Greek crosses. The detector prototype has been tested under the 0.14 THz radiation exposure and showed a voltage response due to the photo-thermoelectric effect up to 0.13–0.18 mV, and voltage responsivity equal to 14–20 mV/W. The detector based on the FSS has shown voltage responsivity up to three times higher in comparison with the detector based on the continuous film. Thermal imaging has shown a temperature increase in the FSS up to 1.5 K under the THz exposure. The obtained results demonstrate prospects for utilization of the Bi88Sb12 FSS detector as a low cost, compact, high-speed, highly sensitive room-temperature THz detector.

Terahertz time-domain spectroscopic polarimetry (THz-TDSP) method was used to experimental study polarization properties of unaligned single-wall carbon nanotube thin films with different geometric parameters on transparent float glass substrates in a frequency range from 0.2 THz to 0.8 THz (corresponding to a wavelength range from ~1.50 mm to ~0.37 mm) ata controlled room temperature of 291–293 K, and a relative humidity of 40–45 %. Frequency dependences of azimuth and ellipticity angles of a polarization ellipse of electromagnetic waves transmitted through the samples were obtained for values of 0.2 Wcm−2, 0.6 Wcm−2, and 1.0 Wcm−2 of an external 980 nm optical pumping, with an external static magnetic field of ~0.3 T. Polarization properties were calculated from temporal waveforms of signals transmitted through the samples at the parallel and the crossed by 45° positions to a transmission direction of the polarizers. A change of 15° in the azimuth angle, and of 10° in the ellipticity angle was achieved. The results show that by using carbon nanomaterials-based structures it is possible to devise efficient and affordable magneto-optically tunable polarization modulators that can be used in the advanced areas of terahertz nanophotonics.

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.

Faraday effect in single-wall carbon nanotubes was experimental studied in a range 0.2–0.8 THz at a room temperature. A change of 15° in an azimuth, and of 10° in an ellipticity angle was achieved.

The results of terahertz time-domain spectroscopy are reported for thin-film Bi, Sb and Bi1−xSbx solid solutions. The influence of film thickness and Sb content on the properties of semimetallic thin films and semimetal film/dielectric substrate structures is studied. It is shown that such semimetal/dielectric structures exhibit hyperbolic permittivity dispersion at low terahertz frequencies, and their effective refractive index can reach values less than 1 and even less than 0. These materials may be used for development of various electronic and optical components which can control the properties of terahertz radiation.

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.

Terahertz time-domain spectroscopic polarimetry (THz-TDSP) method was used to study polarization properties of a few-layer graphene (FLG) on a silicon (Si) substrate in terahertz (THz) frequency range under an external optical pumping and an external static magnetic field. Frequency dependencies of azimuth and ellipticity angles of a polarization ellipse and the polarization ellipse at various frequencies of the electromagnetic waves transmitted through the Si substrate and the FLG on the Si substrate were obtained experimentally and theoretically. The results confirm the fact that, based on the FLG, it is possible to devise efficient tunable THz polarization modulators for use in the latest security and telecommunication systems.

Layers of carbon nanotubes (CNT) with different geometric parameters were applied on narrow bandpass terahertz filter based on cross cavities. Narrow terahertz filter optical parameters were changing during infrared optical pumping of applied CNT layer.

In this study we have obtained refractive indices, absorption coefficients and complex permittivities of mucous and serous fresh somach tissues using terahertz (THz) reflection time-domain spectroscopy. These optical properties were different for each type of the tissue, that can be explained by different morphology of the mucous and serous stomach membranes. The results of the study can be useful for intraoperative diagnostics of gastric cancer localized in different sides of the stomach.

Terahertz wire-grid polarizers are notable for broad bandwidth, high polarization extinction ratio and low transmission loss. This research is dedicated to investigation of anisotropic properties of these polarizers and shows that refractive index can be simply changed by rotating polarization angle of the incident radiation.

nowadays there is a strong necessity of cheap and compact THz components for various THz applications. Photonic crystals (PC) are perspective candidate for this role. In this work we show ability to manipulate broadening of PC band gap by superposition of two different PC lattices.

To evaluate, calibrate equipment, and check the safety of THz devices etc, biotissue phantom is needed for these purposes. Although various researches about biotissue phantom using water have been done, such phantoms are not ideal. Because of the evaporation of water, the optical properties of a phantom change as the time goes by, since THz radiation is very sensitive to the water concentration of the sample. We chose graphite as the substitute of water, and therefore the water-free biotissue phantom was developed to mimic the similar optical properties as human tissues. In order to determine the concentration of each component precisely, quantitative analysis is needed. In this work, we used several mathematical models of the effective medium theory, including the Polder and van Santen model, the Landau, Lifshitz, Looyenga model, the model of complex refractive index, and the Bruggeman model, to study the influence of different graphite concentrations on the refractive index of the water-free biotissue phantom. Phantoms with different graphite concentrations were simulated and 3 phantoms with different graphite concentrations were produced to evaluate the reliability of each model. The fabricated phantoms were then compared with stomach tissues. The result also shows the promise that by using the proper mathematical model, correct concentration can be calculated for other tissue phantom.

Non-invasive diagnostics methods are very helpful for cancer diagnosis and they are a research hotspot in the field of biomedicine. Terahertz (THz) photonics is an emerging technology that can be applied in the field of medical diagnostics. This is due to unique features of THz radiation such as harmlessness to biological tissues, strong absorption by water, ability to identify various biomolecules, etc. In this work we have investigated different types of normal and cancer fresh tissues of the stomach using terahertz time domain spectroscopy in reflection mode. Refractive indices of mucous, serous and tumor stomach tissues were obtained in the frequency range of 0,2 - 1 THz. These optical properties are higher for cancer tissue than for mucosa and lower than for serosa. Thus possibility of discrimination of tumor from normal stomach tissue was demonstrated. This study has practical significance for the field of clinical cancer diagnosis and will help to better understand the specifics of the method of pulsed THz spectroscopy applicable to this field.

The terahertz frequency range is promising for solving various practically important problems. However, for the terahertz technology development, there is still a problem with the lack of affordable and effective terahertz devices. One of the main tasks is to search for new materials with high sensitivity to terahertz radiation at room temperature. Bi1−xSbx thin films with various Sb concentrations seem to be suitable for such conditions. In this paper, the terahertz radiation influence onto the properties of thermoelectric Bi1−xSbx 200 nm films was investigated for the first time. The films were obtained by means of thermal evaporation in vacuum. They were affected by terahertz radiation at the frequency of 0.14 terahertz (THz) in the presence of thermal gradient, electric field or without these influences. The temporal dependencies of photoconductivity, temperature difference and voltage drop were measured. The obtained data demonstrate the possibility for practical use of Bi1−xSbx thin films for THz radiation detection. The results of our work promote the usage of these thermoelectric materials, as well as THz radiation detectors based on them, in various areas of modern THz photonics.

Terahertz time-domain spectroscopic polarimetry (THz-TDSP) method was used to experimental study polarization properties of unaligned single-wall carbon nanotube thin films with di˙erent geometric parameters on transparent float glass substrates in a frequency range from 0.2 THz to 0.8 THz (corresponding to a wavelength range from ∼1.50 mm to ∼0.37 mm) at a controlled room temperature of 291–293 K, and a relative humidity of 40–45 %. Frequency dependences of azimuth and ellipticity angles of a polarization ellipse (PE) of electromagnetic waves transmitted through the samples, and PEs at the frequencies of 0.2 THz, 0.5 THz, and 0.8 THz were obtained for values of 0.2 Wcm − 2, 0.6 Wcm − 2, and 1.0 Wcm − 2 of an external 980 nm near infrared optical pumping, with an external static magnetic field of ∼0.3 T. Polarization properties were calculated from temporal waveforms of signals transmitted through the samples at the parallel and the crossed by 45° positions to a transmission direction of the polarizers. A change of 15° in the azimuth angle, and of 10° in the ellipticity angle was achieved. The results show that by using carbon nanomaterials-based structures it is possible to devise efficient and affordable magneto-optically tunable polarization modulators that can be used in the advanced areas of terahertz nanoscience and nanotechnologies.

The optical properties of the polymer composites consisting of polyvinyl chloride nanofibers and polypropylene films in the frequency range of 0.2–1.0 THz were studied, and the mechanical properties of polyvinyl chloride nanofibers and the structure porosity were investigated. An iterative mathematical model based on effective medium theory was used to describe the effective refractive index and absorption coefficient of the polymer composites. The permittivity tensors of the composites were calculated using the Rytov method. We found that the refractive indices of the composites increased with the increase of polypropylene contents, while absorption coefficients remained the same. The polarization-dependencies of THz optical properties of the composites were relatively low. The proposed composites have the potential to be used as materials for terahertz optical components.

Terahertz time-domain spectroscopic polarimetry (THz-TDSP) method was used to study of polarization properties of a few-layer graphene (FLG) and a randomly oriented single-walled carbon nanotube (SWCNT) thin film on silicon (Si) substrates in terahertz (THz) frequency range under an external optical pumping (OP) and an external static magnetic field (MF). Frequency dependencies of azimuth and ellipticity angles of a polarization ellipse of the samples were obtained experimentally. The results confirm the fact that, based on carbon nanomaterials, it is possible to devise tunable THz polarization modulators for use in the latest security and telecommunication systems.

Terahertz time-domain spectroscopic polarimetry (THz-TDSP) method was used to study of polarization properties of a randomly oriented single-walled carbon nanotube (SWCNT) thin film on a silicon (Si) substrate in terahertz (THz) frequency range under an external optical pumping (OP) and an external static magnetic field (MF). Frequency dependencies of azimuth and ellipticity angles of a polarization ellipse and the polarization ellipse at various frequencies of the Si substrate and the SWCNT thin film on the Si substrate were obtained experimentally. The results confirm the fact that, based on carbon nanotubes, it is possible to devise efficient tunable THz polarization modulators for use in the latest security and telecommunication systems.

The synthesized graphene monolayer always has restrictions on its physical properties compared to the theoretical model of such material (e.g. area of single film, presence of defects, influence of substrate), so investigation of new graphene-based materials is required to implementation of real efficient terahertz devices. We report an experimental study showing that the conductivity dispersion spectra of modified graphene films (multilayer and intercalated with ferric chloride) in the range from 0.2 to 1.0 THz can be efficiently controlled using infrared optical pumping. It was found that the value of imaginary part of terahertz conductivity spectra of multilayer and intercalated graphene on dielectric substrates increases in absolute value with the rise of the pumping intensity, while the real part does not undergo significant changes. We employ a disorderly stacked multilayer graphene model which takes into account the attenuation of pumping intensity for theoretical analysis of the external optical pumping influence on the THz conductivity spectra of multi-layered graphene. Also, Drude–Smith model was applied to fit conductivity spectra of both multilayered and intercalated graphene samples. The models show adequate agreement with experimentally observed results.

The glucose level of blood can be obtained by terahertz time-domain spectroscopy using refractive index measurement method. The detected refractive indices vary from person to person since the impact of bilirubin and creatinine wasn’t considered. 14 human blood samples were tested using terahertz time-domain spectroscopy. The experiment results show that under the certain concentration of glucose, the refractive index of blood decreases with the increase of bilirubin and creatinine concentration, and thus the concentration of other blood components may also influence on the refractive index of blood. The feasibility of using terahertz time-domain spectroscopy to determine the level of glucose, bilirubin and creatinine qualitatively and quantitatively is provided.

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.

In this work, we study infrared optical pump-induced changes in terahertz conductivity of multi-layer graphene on a silicon substrate using terahertz time-domain spectroscopy. Results indicate that the conductivity and optical parameters of investigated material strongly depend on a pumping intensity and the presence of FeCl 3 molecules intercalation. The findings are helpful for determining the most optically tunable material towards designing of optically controllable terahertz devices based on new two-dimensional material beyond graphene monolayer.