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An Ellipsometric Technique with an ATR Module and a Monochromatic Source of Radiation for Measurement of Optical Constants of Liquids in the Terahertz Range
摘要： Measuring the optical constants of liquids, especially water-containing solutions, is very difficult in the terahertz range. The well-known methods of measurement of the refractive index and absorption coefficient in this range include time-domain spectroscopy and Fourier-transform spectrometry. We have developed a highly sensitive ellipsometry method for measuring the optical constants of liquids using the tunable monochromatic radiation from the Novosibirsk free-electron laser. The ellipsometer is supplemented with an internal reflection module for the measurement of highly absorbing samples. The angle of incidence on the sample in the silicon prism of the module has been optimized for maximum sensitivity to parameters to measure. Measurements of the optical constants of various liquids have been performed, and a sensitivity of 0.01 has been demonstrated.
关键词： Internal reflection ellipsometry,Free electron laser,Aqueous solution,Terahertz range
更新于2025-09-23 15:21:21
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[IEEE 2019 IEEE 2nd Ukraine Conference on Electrical and Computer Engineering (UKRCON) - Lviv, Ukraine (2019.7.2-2019.7.6)] 2019 IEEE 2nd Ukraine Conference on Electrical and Computer Engineering (UKRCON) - Surface and Bulk Wave Modes of Two Dimensional Photonic Crystal Waveguide
摘要： Electrodynamical characteristics of the two-dimensional photonic crystal waveguide are considered. Effect of the width of hollow waveguide channel on the dispersion characteristics and spatial distribution of electric field is analyzed. Slow wave localized modes with phase velocity less than speed of light are supported by photonic crystal waveguide and can be used for synchronization with linear electron beams in the terahertz beam-wave systems. Widening of the waveguide hollow channel does not result in significant decrease of the electric field intensity on the axis of waveguide as occur in metallic slow-wave systems.
关键词： spatial harmonics,dispersion characteristics,two-dimensional photonic crystal waveguide,terahertz range,slow wave modes
更新于2025-09-11 14:15:04
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Handbook of Graphene || Modelling of Graphene Nanoribbons Antenna Based on MoM‐GEC Method to Enhance Nanocommunications in Terahertz Range
摘要： In this chapter, we present an electromagnetic modelling formulation of graphene nanoribbon antenna based on moments method combined to the generalized equivalent circuit method (MoM-GEC). The electrical properties of graphene are introduced in the mathematical formulation via a quantum mechanical conductivity deduced from the Kubo formalism. The antenna structure is shielded in a rectangular waveguide with electric boundary walls. Next, the global antenna structure is modelled by an electric equivalent circuit to investigate the antenna parameters. It is proved that, graphene nanoribbon-based antenna presents similar performances as well as conventional one, hence allowing to work at terahertz frequencies range. The high input impedance of a single graphene nanoribbon antenna causes an impedance mismatch problem, which requires the use of an antenna array. So, the coupling phenomena have been well studied in order to optimize the antenna response. Obtained numerical results show that the antenna resonant frequency is very sensitive to the variation of the graphene chemical potential. This leads to a reconfigurable antenna by a simple control of bias voltage. On the other hand, it is showed that, at terahertz frequencies, graphene nanoribbon antenna array allows to enhance the far field communication for short distances, which is beneficial for nanocommunications.
关键词： antenna array,nanocommunications,dynamic conductivity,terahertz range,nanoantenna,MoM-GEC method,Graphene nanoribbon
更新于2025-09-11 14:15:04
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On the Fractal Absorption Spectra of Polymers in the Low-Frequency Part of the Terahertz Range
摘要： The power dependence α(ν) ∝ νμ, where μ > 0 is the power exponent which is noninteger in the general case, is observed for amorphous polymers with a small absorption coe?cient α in the low-frequency part of the terahertz range, which approximately corresponds to the frequencies ν from 0.1 to 2–3 THz. This dependence is fractal, which is due to the fractal structure of the polymer macromolecules. In this work, we ?nd the power-law index at room temperature for the absorption coe?cient of some amorphous polymers. This index is determined on the basis of the dynamics of transmission of a broadband picosecond terahertz pulse through the polymer sample, i.e., using the method of the pulse terahertz spectroscopy in the time-domain representation.
关键词： terahertz range,fractal absorption spectra,polymers,fractal structure,power-law index
更新于2025-09-10 09:29:36