FULL ANISOTROPIC MODEL FOR SIMULATING THE INFRARED REFLECTION ABSORPTION SPECTRA (IRRAS) OF SELF-ASSEMBLED MONOLAYERS (SAMS) FROM ALL-ATOM MOLECULAR DYNAMICS SIMULATIONS

It is important to understand the internal molecular structure of molecular monolayers because that determines the physical and chemical properties of their surface. Infrared spectroscopy is a powerful method to measure the molecular orientation, but to fully harness the information, the spectra need to be compared to structural models. A full anisotropic model is established for simulating the infrared reflection absorption spectra (IRRAS) of self-assembled monolayers (SAMs) based on the methods of Allara and Parikh. The primary focus is to bridge the molecular structures from molecular dynamics simulations with the experimental spectra. The methylene and methyl group orientation are used in the simulations to calculate the complex refractive index tensors in the mid infrared (MIR) using experimental data from a reference phase. The Kramers-Kronig relation is used to calculate the frequency dependent refractive index tensor in the MIR from the absorption of each mode. The high frequency part of the refractive index tensor is calculated from atomic bond vectors in the simulation based on the bond polarizabilities. Afterwards, the IRRAS spectra can be computed using the 4×4 transfer matrix method. Finally, the IRRAS spectra of MD simulation results based on proposed SAM structures are compared

Light interaction with multilayer arbitrary anisotropic structure: an explicit analytical solution and application for subwavelength imaging

A systematic analytical approach to simulate the propagation of electromagnetic plane waves in multilayer anisotropic structures, where the layers can have arbitrary oriented optical axis, is presented. The explicit expressions for the vector polarizations of electric and magnetic fields inside a randomly oriented anisotropic medium are derived. The developed algorithm operates with analytic 4×4 matrices to calculate the transmission and reflection coefficients. This algorithm is suitable to investigate the near-field/far-field electromagnetic wave interaction at any angle of incidence for numerous intriguing applications. The procedure is applied to design anisotropic single and multilayer lenses for subwavelength imaging

Electrodynamic Computer Model of a Metal Rod in a Concrete Medium Detection

The main aim of the present work is to describe a generalized electrodynamic model of the specific device operation, which provides detection and measurement of the geometric characteristics of the reinforcement cage in a concrete structure. The result of this study is the design of the device’s receiving-transmitting path that is optimal in a number of parameters, as well as a signal processing algorithm based on the operation of an artificial neural network trained on the generalized computer model output data. In addition to the main functionality of the device being developed, which consists in structureroscopy by the method of radar holography, useful target characteristics may be obtained during its operation: electrophysical parameters of concrete, structural defects, visualization of an object, etc. To solve this problem, on the basis of general radar principles, frequency-modulated continuous wave was chosen as the operating mode of the device. To create an electrodynamic model, the computer-aided design environment Pathwave EM Design (EMPro) 2021 was used. The developed generalized model may be optimized for a large number of parameters. In addition to the position and number of receiving antennas, the list of optimization variables may include parameters of the transmitting antenna (ray width, directivity, near-field distance), their number (i.e., the capacity of the MIMO system), power on the transmitting side, etc. The proposed scheme of the device is presented as the main result. Zeyde K. M., Ronkin M. V., Kalmykov A. A. Electrodynamic computer model of a metal rod in a concrete medium detection. Ural Radio Engineering Journal. 2021;5(2):104–118. (In Russ.) DOI: 10.15826/urej.2021.5.2.002

Electrodynamic computer model of a metal rod in a concrete medium detection

Поступила: 28.05.2021. Принята в печать: 09.06.2021.Received: 28.05.2021. Accepted: 09.06.2021.The main aim of the present work is to describe a generalized electrodynamic model of the specific device operation, which provides detection and measurement of the geometric characteristics of the reinforcement cage in a concrete structure. The result of this study is the design of the device’s receiving-transmitting path that is optimal in a number of parameters, as well as a signal processing algorithm based on the operation of an artificial neural network trained on the generalized computer model output data. In addition to the main functionality of the device being developed, which consists in structureroscopy by the method of radar holography, useful target characteristics may be obtained during its operation: electrophysical parameters of concrete, structural defects, visualization of an object, etc. To solve this problem, on the basis of general radar principles, frequency-modulated continuouswave was chosen as the operating mode of the device. To create an electrodynamic model, the computer-aided design environment Pathwave EM Design (EMPro) 2021 was used. The developed generalized model may be optimized for a large number of parameters. In addition to the position and number of receiving antennas, the list of optimization variables may include parameters of the transmitting antenna (ray width, directivity, near-field distance), their number (i.e., the capacity of the MIMO system), power on the transmitting side, etc. The proposed scheme of the device is presented as the main result.Целью настоящей работы является описание обобщенной электродинамической модели работы специфического устройства, которое обеспечивает обнаружение и измерение геометрических характеристик арматурного каркаса в бетонной конструкции. Результатом настоящего исследование является оптимальная по ряду параметров конструкция приемо-передающего тракта устройства, а также алгоритм обработки сигналов, основанный на работе искусственной нейронной сети, обученной на выходных данных обобщенной компьютерной модели. Кроме основного функционала разрабатываемого устройства, заключающегося в структуроскопии методом радиолокационной голографии, в процессе его работы могут быть получены дополнительные, полезные характеристики цели: электрофизические параметры бетона, дефекты конструкции, визуализация объекта и т. д. Для решения поставленной задачи на основе общих радиолокационных принципов режимом работы излучателя была выбрана линейная частотная модуляция. Для создания электродинамической модели была использована среда автоматизированного проектирования Pathwave EM Design (EMPro) 2021. Разработанная обобщенная модель может быть оптимизирована по большому количеству параметров. Кроме положения и количества приемных антенн, в списке переменных оптимизации могут быть параметры передающей антенны (ширина диаграммы направленности, коэффициент направленного действия, расстояние ближней зоны) их количество (т. е. разрядность MIMO системы), мощность на передающей стороне и т. д. В качестве основного результата приводится предлагаемая схема устройства

Plasmonics in Semiconductors.

This thesis establishes a mathematical, physical and experimental framework for description, characterization, and application of semiconductor plasmonic properties. Plasmonic phenomena in semiconductors are found in the Terahertz and far-infrared domain, where they have the potential to improve sensors or be the basis of novel devices. III-V semiconductor samples (GaAs, InP, InSb, and InAs) with various doping were analyzed spectroscopically in broad spectral range. Fourier Transform Infrared Spectroscopy together with Terahertz time-domain spectroscopy were used for characterization of the free carrier (plasmonic) and lattice (phononic) optical properties of the samples. The Drude-Lorentz model was used to describe these properties, with the addition of magneto-optical (MO) effects. High mobility semiconductors (InSb and InAs) exhibit huge free carrier magneto-optical effect for small external magnetic field. These measurements were compared to electric Hall effect measurement using Van der Pauw method. Based on the spectroscopic and MO characterization of the samples, the applicability of semiconductor as plasmonic materials is discussed. Huge advantage of semiconductors is the tunability their plasmonic properties. Three methods of controlling the plasmonic behavior of semiconductors were analyzed: Shifting of plasma frequency to higher frequencies by increasing of n-type doping concentration. Modification of the material permittivity (conductivity) tensor spectra by the external magnetic field. Shifting of plasmonic resonance by generation of nanogratings in the material, either by carrier concentration modulation by interference light illumination (sinusoidal grating) or by lithography (lamellar grating). The effective medium approximation of nanogratings was verified using Rigorous Coupled Wave Analysis. An experimental application of widely tunable THz surface plasmon resonance sensor on semiconductors is presented. Generation of surface plasmon polariton at the interface between undoped InSb(InAs) and dielectric is experimentally demonstrated. This sensor has the added functionality of strong magnetic tuning. The applicability of this sensor is discussed, along with analysis of different sensor architecture.Tato práce zavádí matematický, fyzikální a experimentální rámec pro popis, charakterizaci a aplikaci plasmonických vlastností polovodičů. Plasmonické jevy v polovodičích jsou přítomny v terahertzové a daleké infračervené oblasti, kde mohou posloužit k vývoji nových zařízení nebo zlepšení stávajích senzorů. Vzorky III-V polovodičů (GaAs, InP, InSb a InAs) s různým stupněm dopování byly analyzovány spektroskopicky v široké spektrální oblasti. Infračervné spektroskopie s Fourierovou transformací a terahertzová spektroskopie v časové doméně byly použity pro charakterizaci optických vlastností volných nosičů náboje (plasmonické vlastnosti) a optických vlastností vibrací atomové mřížky (fononické vlastnosti). K popsání těchto vlastností byl použit Drude-Lorentzův model, i s přidanou teorií pro popis magneto-optických jevů. Polovodiče s vysokou mobilitou nosičů náboje (InAs, InSb) vykazují obrovské magneto-optické jevy pro malé externí magnetické pole. Tyto optická měření byla porovnána s elektrickým měřením Hallova jevu pomocí Van der Pauwovy metody. Z výsledků spektroskopických a magneto-optických měření vzorků je diskutována použitelnost polovodičů jako plasmonických materiálů. Výhodou polovodičů možnosti ladění jejich plasmonických vlastností. Tři metody ladění byly analyzovány: Zvyšování plasmonické frekvence pomocí n-dopování příměsemi. Změna materiálové permitivity a vodivosti pomocí magnetického pole. Změna plasmonické rezonance pomocí nanomřížek (efektivního prostředí), ať už vyrobenými pomocí změny dopování vzniklé interferenčním osvitem (sinusové mřížky) nebo litografickými metodami (lamelární mřížky). Aproximace efektivním prostředím nanomřížek byla ověřena pomocí rigorózní teorie vázaných vln. Je prezentováno experimentální ověření široce laditelného terahertzového senzoru založeného na bází rezonance povrchového plasmonu. Tento senzor má možné ladění díky externímu magnetickému poli. Použitelnost tohoto senzoru a analýza odlišné architektury senzoru jsou diskutovány.516 - Institut fyzikyvyhově

SCATTERING OF LIGHT BY PLASMONIC AND DIELECTRIC NANOPARTICLES & ITS APPLICATION IN SUBWAVELENGTH IMAGING

Ph.DDOCTOR OF PHILOSOPH

Identifying the experimental and theoretical effective characteristics of nonaligned anisotropic metamaterials

Previous research into anisotropic materials has assumed certain properties in order to make the underlying mathematics tractable. One of the assumptions is the alignment of the optical axes with the laboratory frame of reference, such as split-ring resonators lying at on the material plane. This assumption does not hold true for many metamaterials, such as tilted nanorods. Techniques such as ellipsometry are needed to analyze the effective characteristics of these highly anisotropic structures. In this research, tilted nanorods are analyzed using generalized ellipsometry to extract the indices of the optical axes. The underlying physics of ellipsometry is then used to create a new effective characterization technique called Permittivity and Permeability Tensor Extraction (PPTE), which makes fewer assumptions about the underlying structure of the material and allows for the analysis of a much larger class of structures. PPTE is used to find the effective characteristics of several structures, such as a structure with anisotropy-inducing inclusions and the tilted nanorods. Finally, PPTE is used to begin to examine some of the underlying presumptions about how metamaterials operate, demonstrating that some of the classically used models for calculating permittivity tensors are approximations. The utility of these models in determining the permittivity tensor is studied for several different materials with different properties