Dissertations / Theses: 'THz quasi time domain'

1

Cluff, Julian. "Time domain THz spectroscopy of semiconductors." Thesis, University of Bath, 2000. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.311454.

Full text

APA, Harvard, Vancouver, ISO, and other styles

2

See, Chan H. "Computation of electromagnetic fields in assemblages of biological cells using a modified finite difference time domain scheme. Computational electromagnetic methods using quasi-static approximate version of FDTD, modified Berenger absorbing boundary and Floquet periodic boundary conditions to investigate the phenomena in the interaction between EM fields and biological systems." Thesis, University of Bradford, 2007. http://hdl.handle.net/10454/4762.

Full text

Abstract:

yes
There is an increasing need for accurate models describing the electrical behaviour of individual biological cells exposed to electromagnetic fields. In this area of solving linear problem, the most frequently used technique for computing the EM field is the Finite-Difference Time-Domain (FDTD) method. When modelling objects that are small compared with the wavelength, for example biological cells at radio frequencies, the standard Finite-Difference Time-Domain (FDTD) method requires extremely small time-step sizes, which may lead to excessive computation times. The problem can be overcome by implementing a quasi-static approximate version of FDTD, based on transferring the working frequency to a higher frequency and scaling back to the frequency of interest after the field has been computed. An approach to modeling and analysis of biological cells, incorporating the Hodgkin and Huxley membrane model, is presented here. Since the external medium of the biological cell is lossy material, a modified Berenger absorbing boundary condition is used to truncate the computation grid. Linear assemblages of cells are investigated and then Floquet periodic boundary conditions are imposed to imitate the effect of periodic replication of the assemblages. Thus, the analysis of a large structure of cells is made more computationally efficient than the modeling of the entire structure. The total fields of the simulated structures are shown to give reasonable and stable results at 900MHz, 1800MHz and 2450MHz. This method will facilitate deeper investigation of the phenomena in the interaction between EM fields and biological systems. Moreover, the nonlinear response of biological cell exposed to a 0.9GHz signal was discussed on observing the second harmonic at 1.8GHz. In this, an electrical circuit model has been proposed to calibrate the performance of nonlinear RF energy conversion inside a high quality factor resonant cavity with known nonlinear device. Meanwhile, the first and second harmonic responses of the cavity due to the loading of the cavity with the lossy material will also be demonstrated. The results from proposed mathematical model, give good indication of the input power required to detect the weakly effects of the second harmonic signal prior to perform the measurement. Hence, this proposed mathematical model will assist to determine how sensitivity of the second harmonic signal can be detected by placing the required specific input power.

APA, Harvard, Vancouver, ISO, and other styles

3

Kumar, Manoj. "The development of on-chip THz time-domain spectroscopy." Thesis, University of Leeds, 2016. http://etheses.whiterose.ac.uk/13974/.

Full text

Abstract:

Since the development of efficient THz sources, THz-TDS has been proved to be a promising tool to probe directly the intermolecular modes, rotational motion and intermolecular vibrations of molecules in a variety of chemicals capable of extracting useful spectroscopic information. In this thesis, an on-chip spectroscopy system based on coplanar waveguide (CPW) technology has been designed, optimised and tested, in order to probe spectral features of overlaid polycrystalline materials. As proof of principle, this system was used to recover the THz spectra of α-lactose monohydrate, observing spectral features at ~ 0.53 THz and ~ 1.37 THz. A significant frequency shift in the 1.37 THz feature was observed when the on-chip spectroscopy measurements were performed over a variable temperature range of (~ 6-293 K). Spectral features obtained from the on-chip system were also compared to those obtained from a free-space THz-TDS system to highlight the benefits of using an on-chip system over free space THz-TDS. A theoretical model developed using Ansoft HFSS tool was then used to optimise device design parameters in the second generation of CPW devices. In doing so, the bandwidth of the system was enhanced from ~ 0.42 to 1.6 THz and a much higher frequency resolution of (~ 2 GHz) was obtained compared to that of the first-generation CPW devices (~ 55 GHz) with the modified device design of second generation devices. Branching waveguide systems (THz Y-splitter and coupler) were also simulated, fabricated and measured in order to investigate THz pulse splitting in branching waveguides. These systems allow the measurement of both a sampled and reference pulse. During these measurements, the splitting of the THz pulses propagating in an on-chip THz system was also demonstrated for the first time.

APA, Harvard, Vancouver, ISO, and other styles

4

See, Chan Hwang. "Computation of electromagnetic fields in assemblages of biological cells using a modified finite difference time domain scheme : computational electromagnetic methods using quasi-static approximate version of FDTD, modified Berenger absorbing boundary and Floquet periodic boundary conditions to investigate the phenomena in the interaction between EM fields and biological systems." Thesis, University of Bradford, 2007. http://hdl.handle.net/10454/4762.

Full text

Abstract:

There is an increasing need for accurate models describing the electrical behaviour of individual biological cells exposed to electromagnetic fields. In this area of solving linear problem, the most frequently used technique for computing the EM field is the Finite-Difference Time-Domain (FDTD) method. When modelling objects that are small compared with the wavelength, for example biological cells at radio frequencies, the standard Finite-Difference Time-Domain (FDTD) method requires extremely small time-step sizes, which may lead to excessive computation times. The problem can be overcome by implementing a quasi-static approximate version of FDTD, based on transferring the working frequency to a higher frequency and scaling back to the frequency of interest after the field has been computed. An approach to modeling and analysis of biological cells, incorporating the Hodgkin and Huxley membrane model, is presented here. Since the external medium of the biological cell is lossy material, a modified Berenger absorbing boundary condition is used to truncate the computation grid. Linear assemblages of cells are investigated and then Floquet periodic boundary conditions are imposed to imitate the effect of periodic replication of the assemblages. Thus, the analysis of a large structure of cells is made more computationally efficient than the modeling of the entire structure. The total fields of the simulated structures are shown to give reasonable and stable results at 900MHz, 1800MHz and 2450MHz. This method will facilitate deeper investigation of the phenomena in the interaction between EM fields and biological systems. Moreover, the nonlinear response of biological cell exposed to a 0.9GHz signal was discussed on observing the second harmonic at 1.8GHz. In this, an electrical circuit model has been proposed to calibrate the performance of nonlinear RF energy conversion inside a high quality factor resonant cavity with known nonlinear device. Meanwhile, the first and second harmonic responses of the cavity due to the loading of the cavity with the lossy material will also be demonstrated. The results from proposed mathematical model, give good indication of the input power required to detect the weakly effects of the second harmonic signal prior to perform the measurement. Hence, this proposed mathematical model will assist to determine how sensitivity of the second harmonic signal can be detected by placing the required specific input power.

APA, Harvard, Vancouver, ISO, and other styles

5

Ma, Yong. "THz time domain spectroscopy and its application in biological sciences." Thesis, University of Essex, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.496274.

Full text

APA, Harvard, Vancouver, ISO, and other styles

6

Tuo, Mingguang, Min Liang, Jitao Zhang, and Hao Xin. "Time-Domain THz Near-Field Imaging Incorporating Hadamard Multiplexing Method." IEEE, 2016. http://hdl.handle.net/10150/622785.

Full text

Abstract:

Photoconductive antenna (PCA) array based THz near-field imager incorporating Hadamard multiplexing method is developed in this work. By using a 2 × 2 dipole antenna array as the THz transmitter, the system signal-to-noise ratio (SNR) is demonstrated to be improved by a factor of 2 as the theory predicts. Additionally, a 2-D scanning of a metallic structure on a THz-transparent substrate (with a total scanning area of 1 × 1 mm2) is experimentally implemented. Correlation coefficient estimation is made afterwards to quantify the reconstructed image quality.

APA, Harvard, Vancouver, ISO, and other styles

7

Bandaranayake, B. M. Bimali S. "Terahertz time domain spectroscopy (THz-TDS) for solid state analysis." Diss., University of Iowa, 2016. https://ir.uiowa.edu/etd/3046.

Full text

Abstract:

Terahertz time-domain spectroscopy (THz-TDS) probes inter-molecular interactions within solid materials. THz-TDS covers the spectral region of 0.1-3 THz or 5-100 cm-1 which is a low energy and non-ionizing region of the electromagnetic spectrum. Spectra are collected in a time-domain configuration where a coherent broad-band pulse of THz electromagnetic radiation passes through a sample and gated-detection is used to monitor the electric-field vector of the transmitted THz radiation. This methodology permits a direct measure of the time-of-flight of THz radiation through the sample and, as a result, provides a direct means to measure interactions between the propagating THz electromagnetic wave and the sample material. Time of interaction between the THz wave and the sample gives a measure of the optical and electronic properties of the material and attenuation of the propagating THz wave gives information pertaining to both absorption and scattering properties of the sample. The analytical utility of these features of THz-TDS is explored in this dissertation. Cocrystals represent a novel class of supra-molecular materials composed of two or more inorganic or organic units (molecules, ions or atoms) configured within a crystalline structure. The components interact by hydrogen bonding, π-π stacking or weak Vander Waals interactions to create ordered structures with unique chemical and physical properties. The potential of such unique properties has spurred efforts to design cocrystal materials specifically direct toward long-standing problems within the fields of pharmaceutics and electronics. Research findings presented in this dissertation demonstrate the potential of THz-TDS as an analytical tool for characterizing fundamental chemical and physical properties of cocrystal materials, thereby providing the means to advance the rational design of cocrystal materials for selected applications. The analytical utility of THz-TDS is established through a series of transmission measurements through samples composed of the cocrystal of interest embedded within a polymeric matrix. Both high-density polyethylene and polytetrafluoroethylene are used to form compressed pellets containing cocrystals for analysis. Initial efforts demonstrate quantitation of cocrystalline materials within such pellets through a Beer-Lambert relationship where the magnitude of selected absorption bands is related to the amount of a cocrystal within a given pellet. In addition, time-domain THz spectra are used to determine the refractive index of sample pellets and this information is shown to provide dielectric spectra at THz frequencies for the cocrystal components of the sample pellets. The so-called LLL model is applied to generate accurate dielectric information for the cocrystal component of these pellets on the basis of volume fraction. The ability to measure the polarizability of cocrystals is also demonstrated by applying the Clausius-Mossitti relationship between polarizability and dielectric spectra. The utility of the established analytical features of THz-TDS is demonstrated in a series of preliminary experiments designed to: 1) follow the single-crystal-single-crystal (SCSC)[2+2] photodimerization reaction of 2(5-cyano-resorcinol)∙2(trans-1,2-bis(4-pyridyl)ethylene) to produce rctt-tetrakis(4-pyridyl) cyclobutane; 2) establish the relationship between polarizability and hardness for a series of cocrystals; and 3) determine differences in polarization of cocrystals produced by different synthetic methods. Results support the following conclusions: 1)kinetics of SCSC reactions can be followed through dielectric measurements, but concentration measurements are confounded by unique spectroscopic features observed for partially reacted cocrystals; 2) polarizability at THz frequencies are inversely related to hardness of the tested cocrystals; 3) differences are observed in the polarizability of macro versus nano size cocrystals; and 4) polarizability of these cocrystals is independent of synthesis method.

APA, Harvard, Vancouver, ISO, and other styles

8

Koral, Can. "Experimental Investigation Of Nanofluids Using Terahertz Time Domain Spectroscopy (thz Tds)." Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614424/index.pdf.

Full text

Abstract:

In this study, suspensions of metallic nanoparticles in base fluids, nanofluids, are investigated by using terahertz time domain spectroscopy (THz-TDS). Nanofluids are used as the working fluid in a variety of applications especially for the purpose of heat transfer enhancement. Polar fluids are being used as the base in nanofluids for their tendency to stop aggregation and sedimentation. Polar fluids highly absorb THz signal. In order to select the best possible host, various polar liquids have been investigated, and isopropanol (99.5%) is selected to be the best candidate for its low THz absorptivity when compared to ethanol (99.5%), ethylene glycol (99%), methanol (95%) and distilled water. Ag, Pd and Cu nanoparticles have been custom-made in isopropanol by laser ablation method, and the size distributions have been characterized by Zeta Potential Analyzer. The nanoparticle diameters are measured to be on average 10 nm, 12 nm and 75 nm for Ag, Cu and Pd, respectively. Nanofluids of 1X, 2X and 3X concentrations of Ag, Cu and Pd nanoparticles have been prepared by diluting with pure (99.5%) isopropanol. Measurements have been repeated after 7 days up to 12 days in order to check for aggregations and sedimentations. THz-TDS is a strong tool to analyze the refractive index and absorption coefficient, but no distinct difference was observed in the frequency domain analysis for the nanofluid samples. On the other hand, in the time domain data analysis, a shift on the time data with a change in transmission was observed. For Ag nanoparticles a positive time shift with a decrease in transmission with increasing concentration was observed. For Cu nanoparticles an interesting negative time shift and an increase in the intensity was observed with increasing concentration. The Pd nanoparticle solution scans showed almost no shift initially, but a negative time shift after a wait period on the order of days. A model of the transmission of the THz pulse through the nanofluid was developed based on transmission/reflection coefficients due to both dielectric and conducting layered media. The model well explains the positive time shift seen with Ag nanoparticle suspensions but fails to explain the shift seen with the Cu nanoparticle suspensions due to the long path length inside the nanofluid. Negative time-shifts can only be explained by decreasing the path length which suggests additional layering inside the nanofluid medium, or assuming that the chemical composition of the isopropanol host has changed with the addition of Cu and/or Pd nanoparticles. The positive time shifts observed with the Ag nanoparticle suspensions allowed for estimating the change in refractive index of the base fluid. From this change, using effective medium theory based on Maxwell-Garnett model, the concentrations of the nanoparticles were estimated. The results agree within an order of magnitude to commercially available nanofluids which are also non-aggregate.

APA, Harvard, Vancouver, ISO, and other styles

9

Hissen, Huzifa Zain Alabdeen Abdarahman. "Spectral characterization of materials using terahertz time domain spectroscopy (THz-TDS)." Thesis, Stellenbosch : Stellenbosch University, 2014. http://hdl.handle.net/10019.1/96030.

Full text

Abstract:

Thesis (MSc)--Stellenbosch University, 2014.
ENGLISH ABSTRACT: Terahertz (THz) radiation is often used in many promising applications such as information and communication technology and airport security. Optimized and adapted terahertz fields hold huge promise for leading this technology further. This study is focused on terahertz time domain spectroscopy (THz-TDS). In THz-TDS the electric field is measured, therefore both amplitude and phase information of the THz pulse can be obtained. We used the pump-probe technique in order to measure a THz pulse from the photoconductive antenna. A pulsed fiber laser with FWHM of ' 100 fs was used for this. The frequency spectrum of the measured THz pulse was obtained via a fast Fourier transform. We studied the principles of the THz pulse generation as well as detection, with a photoconductive antenna as emitter and detector. In this study terahertz spectroscopy has been used to investigate the refractive index and absorption coefficient of different types of materials in the terahertz region. The last part of this study deals with a simple process for material parameter extraction of a polymer sample using commercial software called Teramat1.0. It uses the sample thickness, the reference THz pulse and the transmitted THz pulse to retrieve the complex refractive index of the sample.
AFRIKAANSE OPSOMMING: Terahertz (THz) straling word gereeld gebruik vir belowende toepassings soos inligting en kommunikasie tegnologie en lughawe sekuriteit. Geoptimeerde en aangepaste terahertz velde dra by tot die bevordering van die tegnologie. Hierdie studie fokus op terahertz tyd domein spektroskopie (THz-TDS). In THz-TDS word die elektriese veld gemeet en dus word beide amplitude en fase inligting van die THz puls verkry. Ons gebruik ’n pomp en toets tegniek om die THz puls deur ’n fotogeleidende antenna te bepaal. ’n Gepulseerde vesel laser met FWHM van 100 fs word hiervoor benut. Die frekwensie spektrum van die gemete THz puls word bereken deur ’n vinnige Fourier transvorm te bereken. Die beginsels van die generering en deteksie van THz pulse is bestudeer met ’n fotogeleidende antenna as sender en ontvanger. In die studie is terahertz spektroskopie gebruik om die brekingsindekse en die absorpsie koeffisiënte van verskillende materiale in die terahertz gebied te bepaal. Die laaste gedeelte van die studie handel oor ’n eenvoudige proses om die materiaal parameters van ’n polimeer te bepaal deur gebruik te maak van kommersiële sagteware Teramat 1.0. Die monster dikte, die THz verwysingspuls en die deurgelate puls word gebruik om die komplekse brekingsindeks van die materiaal te bereken.

APA, Harvard, Vancouver, ISO, and other styles

10

Glancy, Paul Michael. "Terahertz time domain spectroscopy (THz-TDS) of hydrated biomolecular polymers and monomers." Diss., UC access only, 2009. http://proquest.umi.com/pqdweb?index=153&did=1906549291&SrchMode=1&sid=1&Fmt=7&retrieveGroup=0&VType=PQD&VInst=PROD&RQT=309&VName=PQD&TS=1270496277&clientId=48051.

Full text

Abstract:

Thesis (Ph. D.)--University of California, Riverside, 2009.
Vita. Includes abstract. Includes bibliographical references (leaves 148-155). Issued in print and online. Available via ProQuest Digital Dissertations.

APA, Harvard, Vancouver, ISO, and other styles

11

Senarath, Aditha Srikantha. "Finite Different Time-Domain Simulation of Terahertz Waves Propagation Through Unmagnetized Plasma." Wright State University / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=wright1629431383655508.

Full text

APA, Harvard, Vancouver, ISO, and other styles

12

Erozbek, Gungor Ummugul. "Development Of A Compact Time-domain Terahertz Spectrometer Using Photoconductive Antenna Detection Method." Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/3/12610440/index.pdf.

Full text

Abstract:

In this thesis, we describe the development of a time-domain terahertz (THz) spectrometer driven by two different laser sources: an Er-doped femtosecond fiber laser and a mode-locked Ti:Sapphire laser. The resulting THz electromagnetic radiation was generated and detected using photoconductive antenna detection methods in both systems. In these experiments we characterized the THz power output for both the fiber laser driven system and the Ti:Sapphire laser driven system. Emphasis is given throughout this thesis on understanding the working principles behind time-domain terahertz spectroscopy, applications of THz radiation and terahertz generation as well as terahertz detection methods. We calculated the THz power output using two different methods. By using the &ldquo
Hertzian Dipole&rdquo
method we estimated the generated THz power after the generation photoconductive antenna. Using this method, we showed that the v generated power is on the order of milliwatts, which is far larger than the expected power typical for these systems. The second, &ldquo
Open-Circuit Voltage&rdquo
method, allowed us to calculate the received power on the detection photoconductive antenna. Using this method we were able to show that the THz power generated and detected in these systems is on the order of microwatts. For the mode-locked fiber laser driven spectrometer we obtained on average a ~ 4 ps (0.25 THz) pulse length which corresponded to an average power in the range of 71.8 nW - 70.54 &
#956
W on a dipole antenna with a 6 &
#956
m dipole gap and 44 &
#956
m dipole length. Using the mode-locked Ti:Sapphire laser driven spectrometer we observed a ~ 2 ps (0.5 THz) pulse length and average power in the range of 0.54 nW &ndash
5.12 &
#956
W on a different dipole antenna with a 5 &
#956
m gap and 40 &
#956
m dipole length. Since these values agree with expected values for these systems we believe the &ldquo
Open-Circuit Voltage&rdquo
method is appropriate when trying to calculate the THz power.

APA, Harvard, Vancouver, ISO, and other styles

13

Yu, Yiran. "Measurement of Coating Thickness Based on Terahertz Time-Domain Spectroscopy (THz-TDS) Technology." Thesis, KTH, Fysik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-231335.

Full text

APA, Harvard, Vancouver, ISO, and other styles

14

Bañuelos, Saucedo Miguel Angel. "Signal and data processing for THz imaging." Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/signal-and-data-processing-for-thz-imaging(58a646f3-033b-4771-b1dc-d1f9fc6dfbf0).html.

Full text

Abstract:

This thesis presents the research made on signal and data processing for THz imaging, with emphasis in noise analysis and tomography in amplitude contrast using a THz time-domain spectrometry system. A THz computerized tomography system was built, tested and characterized. The system is controlled from a personal computer using a program developed ad hoc. Detail is given on the operating principles of the system’s numerous optical and THz components, the design of a computer-based fast lock-in amplifier, the proposal of a local apodization method for reducing spurious oscillations in a THz spectrum, and the use of a parabolic interpolation of integrated signals as a method for estimating THz pulse delay. It is shown that our system can achieve a signal-to-noise ratio of 60 dB in spectrometry tests and 47 dB in tomography tests. Styrofoam phantoms of different shapes and up to 50x60 mm is size are used for analysis. Tomographic images are reconstructed at different frequencies from 0.2 THz to 2.5 THz, showing that volume scattering and edge contrast increase with wavelength. Evidence is given that refractive losses and surface scattering are responsible of high edge contrast in THz tomography images reconstructed in amplitude contrast. A modified Rayleigh roughness factor is proposed to model surface transmission scattering. It is also shown that volume scattering can be modelled by the material’s attenuation coefficient. The use of 4 mm apertures as spatial filters is compared against full beam imaging, and the limitations of Raleigh range are also addressed. It was estimated that for some frequencies between 0.5 THz and 1 THz the Rayleigh range is enough for the tested phantoms. Results on the influence of attenuation and scattering at different THz frequencies can be applied to the development of THz CW imaging systems and as a point of departure for the development of more complex scattering models.

APA, Harvard, Vancouver, ISO, and other styles

15

Yeng, Zang. "A fundamental critical assessment of efficiencies in terahertz time-domain spectroscopy systems." Thesis, Queen Mary, University of London, 2017. http://qmro.qmul.ac.uk/xmlui/handle/123456789/24855.

Full text

Abstract:

The electric properties of materials in the THz spectrum are of significant interest for scientific research in the past two decades thanks to the development of THz-TDS systems. However, the measurement capability of the system is still bound by the low efficiency and instability of the system. In this work, a thorough assessment of the THz-TDS system is carried out in order to enhance the measurement capability of the system and provide guidelines for accurate and repeatable measurements. In Chapter 2, the operation fundamentals of THz-TDS systems including the generation and detection are reviewed. The limitations of THz-TDS systems are evaluated in the aspects of dynamic range, signal-to-noise ratio, and spectral resolution. The influence of systematic parameters are addressed and examined. In Chapter 3, a systematic characterisation of the performance of PCAs is performed. The performance of THz PCA is evaluated with respect to the intrinsic and extrinsic excitation parameters, as well as the power collection efficiency within the THz-TDS system. Performance evaluation is carried out in combination of experimental measurements and numerical modellings. Chapter 4 extensively investigates the sensitivity of the THz-TDS system regarding on misalignment of the components. An EM simulation model is built for the evaluation. Point E-field respond in frequency domain and time-domain are examined corresponding directly to the detection signal, and compared with lab measurements. The model is then extended to study the field distribution inside the system. Mode analysis of the field is conducted to discover the pattern of energy coupling related to misalignment. Chapter 5 aims to further enhance the efficiency and radiation characteristics of THz PCAs by adapting the concept of antenna array. The influence of array configuration is assessed by array factor analysis. Coupling conditions of array parameters are established. Performance dependences of THz PCAs on the array geometrics are extensively studied in theory, and tested against experiment. Chapter 6 assess the implementation of plasmonoic structures for the improvement of efficiency and power at the THz generation process. Fundamentals are discussed and structures are designed accordingly. Optimisation principles in consideration of the carrier properties are proposed and practised. Photoconductive antennas with plasmonic structures are fabricated and tested in a THz-TDS system, and the results are compared with simulation.

APA, Harvard, Vancouver, ISO, and other styles

16

Xia, Chen. "Terahertz Time-Domain Spectroscopy of Low-Dimensional Materials and Photonic Structures." Case Western Reserve University School of Graduate Studies / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=case1355168322.

Full text

APA, Harvard, Vancouver, ISO, and other styles

17

Pan, Yi. "Terahertz time-domain spectroscopy and near-field imaging of microstructured waveguides." Thesis, University of Bath, 2013. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.607613.

Full text

Abstract:

This thesis presents studies of novel terahertz photonic devices, including photoconductive optoelectronic devices and guided-wave components, aimed at the development of next-generation terahertz systems. In chapter 2, a scalable interdigitated THz transmitter is designed to increase the output power and compared with a conventional 50 μm coplanar transmitter. In chapter 3, we compare four different receivers with different antenna geometries in terms of bandwidth and sensitivity. Then we describe a photoconductive near-field detector with a subwavelength aperture and its system integration and characterization. In chapter 4, a parallel metal plate waveguide is designed with an integrated step inside the waveguide that can couple to higher order TM modes efficiently from the TEM mode. In this chapter, we also experimentally and numerically study a 2-dimensionally tapered parallel plate waveguide, by which a free-space THz beam can be focused into a deep subwavelength-scale volume. In chapter 5, a parallel thin dielectric film waveguide is used to explore the guiding mechanism of an antiresonant optical reflection waveguide. Cylindrical silica single capillaries and a microstructured capillary, which guide in a similar way, are characterized in terms of mode profiles and attenuation. In chapter 6, we study oblique transmission through freestanding thin nickel films, which are perforated with periodic conical hole arrays. Surface modes can be supported by both metallic surfaces with different nonlinear dispersion curves, which results in spectral interferences in a near-field region when the surface modes couple out of the waveguide into free space.

APA, Harvard, Vancouver, ISO, and other styles

18

Karaoglan, Gulten. "Investigation Of Dc Generated Plasmas Using Terahertz Time Domain Spectroscopy." Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/3/12612070/index.pdf.

Full text

Abstract:

This thesis is on the topic of investigation of the characteristics of DC Glow Discharge plasmas. Emphasis is given on characterizing the plasma electron density. The methods of generating and detecting THz pulses are described. THz transmission spectroscopy and plasma emission spectroscopy is examined. Transmission spectrum is taken for Air, gaseous Nitrogen and Argon plasmas. Moreover, emission spectrum of Air, N2 and Ar plasma analysis were done respectively. It was found that the transmission of terahertz pulses through nitrogen plasma was considerably affected compared to that of the argon plasma. Initially Drude model theory of electron conduction is employed to analyze the plasma density.

APA, Harvard, Vancouver, ISO, and other styles

19

Smith, Ryan Michael. "Terahertz frequency analysis of gaseous and solid samples using terahertz time-domain spectroscopy." Diss., University of Iowa, 2012. https://ir.uiowa.edu/etd/3386.

Full text

Abstract:

Developments in semiconductor and laser technologies have facilitated development of terahertz (THz)-frequency (˜2-200 cm-1) technologies. Results published in the literature as far back as the early 20th century demonstrate the utility of this frequency range for myriad applications, but the improved performance of modern THz technologies has renewed interest in THz-frequency analysis. Material presented in this dissertation focuses on three applications of terahertz time-domain spectroscopy (THz-TDS): quantitation of gas-phase molecular species, analysis of polymeric materials, and investigation of dental tissue/composite structures. Gas phase species were quantified individually at concentrations ranging from several parts per million to several parts per thousand using various chemometric methods. Quantitative model robustness was evaluated by comparison of model precision, and partial least-squares (PLS) regressions provided the greatest precision. Species were quantified in mixtures using PLS with errors of prediction below the permissible exposure limits (PELs) set by the Occupational Safety and Health Administration. The effect of spectral broadening as a result of overall sample pressure was investigated, and species were analyzed in mixtures at various overall pressures. Errors of prediction were again near or below the PELs, demonstrating the utility of this method for atmospheric analysis. Chemical selectivity available in THz spectral features was evaluated and compared to selectivity available in infrared frequencies. Spectral parameters measured in the THz frequency range also provide insight into structural properties of polymeric materials. In some cases, spectral peaks may be used to identify the temperature at which phase changes occur within these materials. THz refractive index spectra were found to be a sensitive and non-destructive tool for identification of phase transition temperatures. The time-resolved measurement of THz-TDS makes it particularly useful for rapid, non-destructive analysis of layered structures. Ordinarily, the strength of bonds between dental tissues and composite materials are evaluated in the laboratory using destructive failure analyses. Transparency of dental tissues and composite materials used for restorative procedures to THz pulses allows investigation of interfaces between these materials. Refractive index spectra indicate locations in which delamination has occurred between bonded layers. These results provide an overview of unique capabilities of the THz-TDS method in real-life spectral analyses.

APA, Harvard, Vancouver, ISO, and other styles

20

Niklas, Andrew John. "Highly-Configurable Multi-Objective Optimization for Physical Parameter Extraction using Terahertz Time-Domain Spectroscopy." Wright State University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=wright1527270199110387.

Full text

APA, Harvard, Vancouver, ISO, and other styles

21

Qiao, Wenchao [Verfasser]. "Liquids and molecular solids investigated by THz time-domain reflection and parallel-plate waveguide spectroscopy / Wenchao Qiao." Konstanz : Bibliothek der Universität Konstanz, 2012. http://d-nb.info/1029291640/34.

Full text

APA, Harvard, Vancouver, ISO, and other styles

22

Walther, Markus. "Modern spectroscopy on biological molecules structure and bonding investigated by THz time-domain and transient phase-grating spectroscopy /." [S.l.] : [s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=970191170.

Full text

APA, Harvard, Vancouver, ISO, and other styles

23

Suzanovičienė, Rasa. "Krūvininkų kinetikos puslaidininkiuose tyrimai naudojant terahercinės spinduliuotės impulsus." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2010. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2010~D_20101116_163938-18022.

Full text

Abstract:

Ultrasparčių puslaidininkinių komponentų kūrimas reikalauja gilesnio supratimo apie tai, kaip puslaidininkiuose vyksta fizikiniai procesai, trunkantys kelias pikosekundes ar net mažiau nei vieną pikosekundę. Tokie reiškiniai, kaip elektronų impulso ir energijos relaksacija bei nepusiausvyrųjų krūvininkų pagavimas yra labai svarbūs puslaidininkinių fotonikos ir terahercinio diapazono prietaisų veikimui. Iki pastarojo meto pagrindinis ultrasparčiųjų procesų puslaidininkiuose tyrimo įrankis buvo optiniai metodai, kuriuose elektronų dinamikai stebėti buvo pasitelkiami pikosekundinių ar femtosekundinių lazerių impulsai. Nepaisant išskirtinai didelės šių metodų laikinės skyros, optinio kaupinimo-zondavimo matavimų rezultatus yra palyginti sudėtinga interpretuoti. Šie rezultatai dažniausiai yra įtakojami kelių sistemos parametrų kitimo ir įvairių fizikinių reiškinių tarpusavio sąveikos, todėl sunkiai susiejamas su kuria nors elektronų laikine charakteristika. Disertacijos darbo tikslas – naudojant terahercinės spinduliuotės impulsus išmatuoti elektronų impulso ir energijos relaksacijos trukmes keliuose siauratarpiuose puslaidininkiuose bei jų gyvavimo trukmes medžiagose, skirtose fotolaidžių terahercinės spinduliuotės emiterių ir detektorių gamybai. Šioje disertacijoje yra pateikiami įvairių charakteringų elektroninius procesus puslaidininkiuose apibūdinančių trukmių matavimų naudojant terahercinės spinduliuotės impulsus rezultatai. Tokie tyrimai atlikti ir optinio žadinimo –... [toliau žr. visą tekstą]
Creation of ultrafast semiconductor components is inconceivable without understanding various processes of picoscond duration in semiconductors. These processes, as electron energy relaxation time or nonequiriblium carrier capture are very important for semiconductor photonics and terahertz range devices. Since now, the most popular tool of measuring ultrafast processes in semiconductors was picosecond or femtosecond laser pulses. In spite of excellent time resolution, optical pump – probe methods have a significant imperfection. Interpretation of the results can be very complicate. Also, the measured result can be affected by few variable parameters or interaction of various physical phenomenon. Therefore determinate results can be hardly related with electron time dependent characteristic. The aim of this dissertation was to measure electron energy relaxation times and electron life times by using terahertz pulses in narrow – gap semiconductors used for photoconductive terahertz emitters or detectors. In this dissertation, electron characteristic times witch describe various processes in semiconductor, were studied. These measurements were performed by optical pump – terahertz probe technique and time domain terahertz spectroscopy. The emission of terahertz pulses from the semiconductor surface, illuminated by femtosecond laser pulses, was investigated.

APA, Harvard, Vancouver, ISO, and other styles

24

Wall, Alexander. "Characterisation of tablets and roller-compacted ribbons with terahertz time-domain pulsed imaging." Thesis, De Montfort University, 2015. http://hdl.handle.net/2086/11152.

Full text

Abstract:

The pharmaceutical process of dry granulation using roller-compaction (DG/RC) is effectively a non-batch based procedure orientated to deliver a continuous stream of material free of a pre-defined batch-size with reduced plant equipment/scale-up R&D resources and an enhanced work-throughput, particularly suitable for moisture sensitive formulation. The desirable accreditations of DG/RC are many; yet by the nature of a more flexible approach than (i.e. wet-granulation), it must be highly monitored and controlled to accomplish higher-throughput rates and reduced ‘static’ material testing stages. To monitor rapidly and in-line with production, pre-granulated ribbons of RC (which highly correlates to the post milled granulates), terahertz time-domain spectroscopy (TDS) is used to elucidate the key physical attributes of post-compression density and thickness uniformity, key to end-product consistency. Invariably a great number of conditions apply to DG/RC (viz: System design, material characteristics, environmental and unit configuration), although widely regarded as the key processing parameters (PP’s) are roll-pressure and roll-gap [1-4]. The target of the study is to derive a strategy to position TDS as PAT to DG/RC. Two terahertz time-domain TD methods of a conventional transmission setup and reflection (TPI) THz analysis are used on standards of glass slides for verifying the interpretational foundations of the TD methods. Achieving RI/thickness error-discrepancies +2.2 to -0.4% c.f. literature ([150]) values provides foundations to test the solid-fraction ratios of pharma tablets with regard to RI’s being surrogate values to SF/path-length (R2 = 1). Combining transmission principles to the portion of reflected EMR removes the pre-requisite for RI or path-length knowledge, giving +1.5 to +2.4% RI agreement (vs. frequency-domain attained results) thus enabling thickness estimations to be above 95% against physical micrometre judgement in all models. Augmentation of the TD methods, refined in Experimental chapter 2 ,then chiefly focuses on TPI as the principle THz-TD method (as the most ideal tool for PAT) for adopting the RI measures for ribbon uniformity analysis in Experimental chapter 4 in an off-line environment again resulting in RI and thicknesses < 5 % error of known parameters of thickness and further use of RI as a proxy porosity equivalent to gas pycnometry. Elucidated in the work are the limitations encountered with tablets and RC’s, data interpretation of industrial considerations. Experimental chapter 3 diverges from RI to differentiate thickness in-order to assess the FD transmission for non-destructive mechanical assessment. This demonstrates a clear relationship between compaction force and the surrogate value for density, following a linear trend below a certain threshold of force. The ‘threshold’ value is observed for less massive tablets, and concluded is that the mechanistic interplay and permanent (plastic) consolidation is greater in instances where compaction-force increases proportionally with target-fill weights, and thus the various behaviour of MCC to stress.

APA, Harvard, Vancouver, ISO, and other styles

25

Sirbu, Marina. "Couplage des équations de Maxwell avec l'équation de Boltzmann en 3D : appliqué à la modélisation d'un photocommutateur THz." Paris 11, 2005. http://www.theses.fr/2005PA112255.

Full text

Abstract:

Cette thèse traite le couplage des équations du transport et des équations de l'électromagnétisme dans un photocommutateur visant la génération des signaux TeraHertz. Dans un premier temps, les équations relatives au transport des porteurs sont résolues avec un modèle " dérive diffusion ". Ensuite une résolution plus complexe basée une approche Monte Carlo est présentée. Le photocommutateur est situé dans un guide coplanaire dont les dimensions sont proches de celles des structures existantes. Les contraintes numériques sont liées à la résolution dans le domaine temporel du système d'équations couplées, au maillage spatial, à la taille du domaine de simulation nécessaire, aux conditions aux limites et aux non- linéarités supplémentaires introduites par la variation temporelle et spatiale des différents coefficients. Le système 3D est entièrement résolu par la méthode FDTD (Finite Difference Time Domain) à pas variable, ce qui nous permet d'avoir un maillage suffisamment fin au sein du dispositif. Nous avons étudié la manière dont est générée la réponse du photocommutateur à une excitation optique femto seconde. Nous avons d'abord mis en évidence l'origine électromagnétique de cette réponse, avant d'effectuer une étude paramétrique permettant l'identification des paramètres clefs qui la contrôlent. La confrontation des résultats de modélisation avec les résultats de mesure existants a montré un bon accord. Les résultats préliminaires obtenus avec la méthode de Monte Carlo ont permis de mettre en évidence des effets inertiels entre les variations du champ électromagnétique et la réponse des porteurs
This PhD thesis presents the coupling between the Boltzmann transport equations and the electromagnetic field equations in a photoconductive switch generating THz signals. First, the transport equations are solved in the drift diffusion approximation. Then, a more complex resolution is made with a Monte Carlo based model. The photoconductive switch is located is coplanar wave guide whose dimensions are comparables with the existents structures. The numerical constraints come from the time dependant resolution, the necessarily space mesh, the simulation domain dimensions, boundary conditions and non linearity introduced by the time and space coefficients variation. The 3D equation system is solved with the variable space step FDTD (Finite Difference Time Domain) method, which allows a sufficiently refined mesh inside the switch. We have studied the photoconductive switch response when a femto second optic excitation is applied. We have shown the electromagnetic field implication in the device response origin. We also made a parametric analysis identifying the main parameters controlling the electromagnetic THz pulse. There is a good agreement between the modelling results and the experimental data. The Monte Carlo method allows taking into account the inertial effects between the electromagnetic field variation and the carrier response. This method is still in developing phase, but we have obtained good preliminary results

APA, Harvard, Vancouver, ISO, and other styles

26

Bičiūnas, Andrius. "Puslaidininkinių medžiagų, skirtų 1 µm bangos ilgio femtosekundiniais lazerio impulsais aktyvuojamų terahercinių optoelektronikos sistemų komponentams, tyrimas." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2012. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2012~D_20121107_091138-15044.

Full text

Abstract:

Disertacijos darbo tikslas buvo sukurti ir ištirti puslaidininkinius terahercinių (THz) impulsų emiterius ir detektorius, skirtus sistemoms, naudojančioms 1 μm bangos ilgio femtosekundinę lazerinę spinduliuotę. THz impulsų generavimo ir detektavimo sistema, kurios optoelektroninius puslaidininkinius komponentus aktyvuoja femtosekundiniai lazerio impulsai, yra plačiai taikoma terahercinėje laikinės srities spektroskopijoje. Tradiciškai tokiose sistemose naudojami Ti:safyre femtosekundiniai lazeriai, kurių spinduliuotės bangos ilgis yra ~800 nm. Šios sistemos nėra patogios dėl jų matmenų, nes lazeriai turi sudėtingą kelių pakopų kaupinimo sistemą. Pastaruoju metu THz impulsų generavimui vis dažniau naudojami femtosekundiniai kietakūniai ir šviesolaidiniai lazeriai, kurių spinduliuotės bangos ilgis patenka į artimosios IR spinduliuotės sritį. Tačiau šios sistemos vis dar neturi tinkamos medžiagos fotolaidiems elementams gaminti, kurie būtų žadinami 1 – 1,55 µm bangos ilgio lazeriais. Tokios medžiagos, visų pirmą, turi būti jautrios optinei spinduliuotei, o jų draustinės energijos tarpas turi atitikti žadinamos spinduliuotės fotonų energiją, be to sluoksniai turi pasižymėti didele tamsine varža bei labai trumpomis krūvininkų gyvavimo trukmėmis (~ 1 ps). Šioje disertacijoje yra pateikiami THz impulsų generavimo panaudojus puslaidininkių paviršius ir fotolaidžias antenas rezultatai, žadinant 1 µm bangos ilgio femtosekundiniais lazerio impulsais.
The aim of dissertation was to develop and explore the semiconductor material terahertz (THz) pulse emitters, for Terahertz time–domain spectroscopy (THz–TDS) systems using a 1 μm wavelength femtosecond laser radiation. THz pulse generation and detection using optoelectronic semiconductor components in THz–TDS excited by femtosecond laser pulses become these days a powerful experimental technique. Traditionally, mode-locked Ti:sapphire lasers emitting at the wavelengths ~800 nm are used. However Ti:sapphire lasers require many-stage optical pumping arrangement, the system is quite bulky and complicated. The solution could be the lasers emitting in 1 – 1.55 µm, which can be directly pumped by diode laser bars. Recently, several compact, efficient and cost-effective solid-state and fiber laser systems that generate femtosecond pulses at near-infrared wavelengths have been developed and employed for activating THz–TDS systems. The main obstacle of these systems is the lack of material with appropriate bandgap, high dark resistivity and short (~ ps) carrier lifetimes.

APA, Harvard, Vancouver, ISO, and other styles

27

Bičiūnas, Andrius. "Semiconductor materials for components of optoelectronic terahertz systems activated by femtosecond 1 µm wavelength laser pulses." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2012. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2012~D_20121107_091148-13422.

Full text

Abstract:

The aim of dissertation was to develop and explore the semiconductor material terahertz (THz) pulse emitters, for Terahertz time–domain spectroscopy (THz–TDS) systems using a 1 μm wavelength femtosecond laser radiation. THz pulse generation and detection using optoelectronic semiconductor components in THz–TDS excited by femtosecond laser pulses become these days a powerful experimental technique. Traditionally, mode-locked Ti:sapphire lasers emitting at the wavelengths ~800 nm are used. However Ti:sapphire lasers require many-stage optical pumping arrangement, the system is quite bulky and complicated. The solution could be the lasers emitting in 1 – 1.55 µm, which can be directly pumped by diode laser bars. Recently, several compact, efficient and cost-effective solid-state and fiber laser systems that generate femtosecond pulses at near-infrared wavelengths have been developed and employed for activating THz–TDS systems. The main obstacle of these systems is the lack of material with appropriate bandgap, high dark resistivity and short (~ ps) carrier lifetimes.
Disertacijos darbo tikslas buvo sukurti ir ištirti puslaidininkinius terahercinių (THz) impulsų emiterius ir detektorius, skirtus sistemoms, naudojančioms 1 μm bangos ilgio femtosekundinę lazerinę spinduliuotę. THz impulsų generavimo ir detektavimo sistema, kurios optoelektroninius puslaidininkinius komponentus aktyvuoja femtosekundiniai lazerio impulsai, yra plačiai taikoma terahercinėje laikinės srities spektroskopijoje. Tradiciškai tokiose sistemose naudojami Ti:safyre femtosekundiniai lazeriai, kurių spinduliuotės bangos ilgis yra ~800 nm. Šios sistemos nėra patogios dėl jų matmenų, nes lazeriai turi sudėtingą kelių pakopų kaupinimo sistemą. Pastaruoju metu THz impulsų generavimui vis dažniau naudojami femtosekundiniai kietakūniai ir šviesolaidiniai lazeriai, kurių spinduliuotės bangos ilgis patenka į artimosios IR spinduliuotės sritį. Tačiau šios sistemos vis dar neturi tinkamos medžiagos fotolaidiems elementams gaminti, kurie būtų žadinami 1 – 1,55 µm bangos ilgio lazeriais. Tokios medžiagos, visų pirmą, turi būti jautrios optinei spinduliuotei, o jų draustinės energijos tarpas turi atitikti žadinamos spinduliuotės fotonų energiją, be to sluoksniai turi pasižymėti didele tamsine varža bei labai trumpomis krūvininkų gyvavimo trukmėmis (~ 1 ps). Šioje disertacijoje yra pateikiami THz impulsų generavimo panaudojus puslaidininkių paviršius ir fotolaidžias antenas rezultatai, žadinant 1 µm bangos ilgio femtosekundiniais lazerio impulsais.

APA, Harvard, Vancouver, ISO, and other styles

28

Poulin, Cyndie. "Etudes des matériaux, composants et systèmes dans le domaine térahertz par analogie aux méthodes optiques." Thesis, Ecole centrale de Marseille, 2018. http://www.theses.fr/2018ECDM0010/document.

Full text

Abstract:

L’objectif de ma thèse est d’étendre les modèles électromagnétiques existants à l’Institut Fresnel pour les fréquences optiques vers le domaine des fréquences térahertz (THz), pour mieux comprendre les phénomènes physiques mis en jeu lors d’interaction onde-matière. Cette compréhension permettrait d’améliorer l’analyse des images THz acquises et de mieux définir les configurations des systèmes optiques utilisés. Ce travail est réalisé en comparant les résultats issus de la modélisation avec ceux provenant d’expériences menées par imagerie THz au sein de l’entreprise Terahertz Waves Technologies. Dans le futur, la modélisation pourrait devenir un outil prédictif pour la caractérisation de matériaux dans le domaine THz.Les ondes THz se situent entre l’infrarouge lointain et les micro-ondes dans le spectre électromagnétique allant de 0.01 mm à 3 mm (ou 100 GHz à 30 THz). Ces ondes bénéficient des avantages des ondes optiques et des micro-ondes dépendant des longueurs d’ondes utilisées. L’imagerie THz présente un fort potentiel pour la caractérisation de la matière, car ces ondes peuvent pénétrer beaucoup de matériaux qui sont opaques dans le visible et dans l’infrarouge. La détection de défauts, les délaminations, la présence d’humidité, etc…, sont un exemple des problématiques qui peuvent être investiguées grâce au rayonnement THz.Dans un premier temps, j’ai pu simuler la réponse optique d’échantillons polymères plans homogènes et isotropes avec de bons accords entre le calcul et la mesure. Ces résultats ont permis de réaliser de premières modélisations d’images en adéquation avec l’imagerie THz. L’étude est ensuite élargie aux matériaux anisotropes qui existent dans l’environnement industriel actuel ainsi qu’aux objets de forme cylindrique. Les modèles développés considèrent l’indice de réfraction complexe d’un échantillon et son épaisseur, c’est pourquoi un chapitre est dévolu à la méthode d’estimation de ces paramètres à partir de mesures issues de spectroscopie THz dans le domaine temporel mise en œuvre
The aim of my thesis is to extend the electromagnetic models already existing at the Institut Fresnel for the optical frequencies towards the terahertz (THz) range, to have a better knowledge of the physical phenomena involved in THz light-matter interactions. This understanding would allow to improve the analysis of the THz images acquired and to have a better definition of the optical systems configurations that we use. To achieve this work, we compare the results coming from the model with those from the experiments led by THz imaging by Terahertz Waves Technologies. In the future, the modelling could become a predictive tool for the characterization of materials in the THz domain.THz waves are located between far infrared and microwaves in the electromagnetic spectrum going from 0.01 mm to 3 mm (or 100 GHz to 30 THz). These waves benefit from advantages of the optical waves and from microwaves depending on used frequencies. THz imaging presents a high potential one for the characterization on the material, because these waves can penetrate a lot of materials which are opaque in the visible and the infrared lights. Detection of defects, delaminations, the presence of humidity, etc…, are examples of the problems which can be investigated with THz light.At first, I was able to model the optical response of planar, homogenous, isotropic and polymeric samples with good agreements between the calculation and the measurement. These results allowed to realize first modellings of images which are consistent with THz imaging. Therefore, the study is enlarged to anisotropic materials which exist in the current industrial environment as well as the objects of full cylindrical shape. The developed models consider the complex refractive index of a sample and its thickness, that is why a chapter is devoted to the method of estimation of these parameters from measurements coming from THz Time-Domain Spectrocopy signals which was implemented

APA, Harvard, Vancouver, ISO, and other styles

29

Dietz, Roman Jürgen Bruno [Verfasser], and Martin [Akademischer Betreuer] Koch. "Photoconductive THz emitters and detectors on the basis of InGaAs/InP for terahertz time domain spectroscopy / Roman Jürgen Bruno Dietz. Betreuer: Martin Koch." Marburg : Philipps-Universität Marburg, 2015. http://d-nb.info/1076865658/34.

Full text

APA, Harvard, Vancouver, ISO, and other styles

30

Meier, Steffen Marius [Verfasser], Uwe [Gutachter] Czarnetzki, and Horst [Gutachter] Fichtner. "Plasmadichtebestimmung mittels Dual-Frequency-Multichannel-Boxcar-THz-Time-Domain-Spektroskopie / Steffen Marius Meier ; Gutachter: Uwe Czarnetzki, Horst Fichtner ; Fakultät für Physik und Astronomie." Bochum : Ruhr-Universität Bochum, 2018. http://d-nb.info/1161942327/34.

Full text

APA, Harvard, Vancouver, ISO, and other styles

31

Yeo, Woon Gi. "Terahertz Spectroscopic Characterization and Imaging for Biomedical Applications." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1430825935.

Full text

APA, Harvard, Vancouver, ISO, and other styles

32

Vazquez, Javier. "Analysis and design of planar active and passive quasi-optical components using new FDTD techniques." Thesis, Queen Mary, University of London, 2002. http://qmro.qmul.ac.uk/xmlui/handle/123456789/28583.

Full text

Abstract:

New Quasi-optical sensor technology, based on the millimetre and submillimetre band of the electromagnetic spectrum, is actually being implemented for many commercial and scientific applications such as remote sensing, astronomy, collision avoidance radar, etc. These novel devices make use of integrated active and passive structures usually as planar arrays. The electromagnetic design and computer simulation of these new structures requires novel numerical techniques. The Finite Difference Time Domain method (FDTD) is well suited for the electromagnetic analysis of integrated devices using active non-linear elements, but is difficult to use for large and/or periodic structures. A rigorous revision of this popular numerical technique is performed in order to permit FDTD to model practical quasi-optical devices. The system impulse response or discrete Green's function (DGF) for FDTD is determined as a polynomial then the FDTD technique is reformulated as a convolution sum. This new alternative algorithm avoids Absorbing Boundary Conditions (ABC's) and can save large amounts of memory to model wire or slot structures. Many applications for the DGF can be foreseen, going beyond quasi-optical components. As an example, the exact ABC based on the DGF for FDTD is implemented for a single grid wall is presented. The problem of time domain analysis of planar periodic structures modelling only one periodic cell is also investigated. Simple Periodic Boundary Conditions (PBC) can be implemented for FDTD, but they can not handle periodic devices (such as phased shift arrays or dichroic screens) which produce fields periodic in a 4D basis (three spatial dimensions plus time). An extended FDTD scheme is presented which uses Lorentz type coordinate transformations to reduce the problem to 3D. The analysis of non-linear devices using FDTD is also considered in the thesis. In this case, the non linear devices are always model using an equivalent lumped element circuit. These circuits are introduced into the FDTD grid by means of the current density following an iterative implicit algorithm. As a demonstration of the technique a quasi-optically feed slot ring mixer with integral lens is designed for operation at 650 GHz.

APA, Harvard, Vancouver, ISO, and other styles

33

Pistore, Valentino. "Modelocking of THz quantum cascade lasers : dispersion control and non-linearities." Electronic Thesis or Diss., Sorbonne université, 2019. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2019SORUS302.pdf.

Full text

Abstract:

Les LCQ THz sont aujourd'hui considérés comme une plate-forme prometteuse pour la génération d’impulsions THz intenses et ultracourtes. En raison de leur temps de récupération du gain rapide, le verrouillage en mode passif des LCQ THz s'est jusqu'à présent révélé difficile. Au contraire, le verrouillage de mode actif avec une modulation hyperfréquence a été appliqué avec succès. La durée du pouls a cependant été difficile à réduire malgré des années de recherche. En 2017, notre groupe a généré des impulsions THz de 4ps grâce à l'application d'une structure intégrée (un GTI) visant à réduire la dispersion chromatique. La recherche dans cette thèse commence à partir de ce point. Je présente notamment l'ingénierie de dispersion dans les LCQ THz afin d'obtenir des impulsions très courtes, même à partir de dispositifs à bande relativement étroite. Ceci est réalisé en utilisant des méthodes de modulation actives éprouvées qui peuvent ajuster l’émission de LCQ d’un régime de dispersion élevé à faible. Je montre également que les LCQ THz peuvent présenter une forte modulation d'amplitude de leur profil d'émission et qu'ils peuvent émettre spontanément des impulsions à la suite d'un mécanisme d’auto-verrouillage. En conséquence, cela indique que le temps de récupération de gain rapide n'est pas un facteur limitant pour la génération d'impulsions. Je montre également ce schéma passif dans le cadre des premières démonstrations du verrouillage en mode harmonique de LCQ THz. Enfin, un nouveau phénomène est présenté où les modes d’une LCQ THz peuvent battre ensemble pour générer une émission de micro-ondes dans l’espace libre
THz QCLs are nowadays considered a promising platform for the generation of intense and ultrashort THz pulses. Owing to their fast gain recovery time, passive modelocking of THz QCLs has so far proved to be difficult. On the contrary, active modelocking with a microwave modulation has been successfully applied. The pulse duration, however, has been arduous to reduce despite years of research. In 2017, THz pulses as short as 4ps have been generated by our group with the application of an integrated structure (a GTI) aiming to reduce the chromatic dispersion. The research in this thesis starts from this point.In particular, I present dispersion engineering in THz QCLs in order to obtain very short pulses even from relatively narrow-band devices. This is achieved using proven active modulation methods that can tune the QCL emission from high to low dispersion regimes. I also show that THz QCLs can present a strong amplitude modulation of their emission profile and that they can spontaneously emit pulses as a result of a self-locking mechanism, contrary to the expected frequency modulated response. As a consequence, this indicates that the fast gain recovery time is not a limiting factor for the generation of pulses. I also show this passive self-locking scheme for passive pulse generation in the framework of the first demonstrations of harmonic modelocking of THz QCLs. Finally, a new phenomenon is presented where the modes of a free running THz QCL can beat together to generate free space microwave emission

APA, Harvard, Vancouver, ISO, and other styles

34

Ramli, Khairun N. "Modelling and analysis of complex electromagnetic problems using FDTD subgridding in hybrid computational methods. Development of hybridised Method of Moments, Finite-Difference Time-Domain method and subgridded Finite-Difference Time-Domain method for precise computation of electromagnetic interaction with arbitrarily complex geometries." Thesis, University of Bradford, 2011. http://hdl.handle.net/10454/5443.

Full text

Abstract:

The main objective of this research is to model and analyse complex electromagnetic problems by means of a new hybridised computational technique combining the frequency domain Method of Moments (MoM), Finite-Difference Time-Domain (FDTD) method and a subgridded Finite-Difference Time-Domain (SGFDTD) method. This facilitates a significant advance in the ability to predict electromagnetic absorption in inhomogeneous, anisotropic and lossy dielectric materials irradiated by geometrically intricate sources. The Method of Moments modelling employed a two-dimensional electric surface patch integral formulation solved by independent linear basis function methods in the circumferential and axial directions of the antenna wires. A similar orthogonal basis function is used on the end surface and appropriate attachments with the wire surface are employed to satisfy the requirements of current continuity. The surface current distributions on structures which may include closely spaced parallel wires, such as dipoles, loops and helical antennas are computed. The results are found to be stable and showed good agreement with less comprehensive earlier work by others. The work also investigated the interaction between overhead high voltage transmission lines and underground utility pipelines using the FDTD technique for the whole structure, combined with a subgridding method at points of interest, particularly the pipeline. The induced fields above the pipeline are investigated and analysed. FDTD is based on the solution of Maxwell¿s equations in differential form. It is very useful for modelling complex, inhomogeneous structures. Problems arise when open-region geometries are modelled. However, the Perfectly Matched Layer (PML) concept has been employed to circumvent this difficulty. The establishment of edge elements has greatly improved the performance of this method and the computational burden due to huge numbers of time steps, in the order of tens of millions, has been eased to tens of thousands by employing quasi-static methods. This thesis also illustrates the principle of the equivalent surface boundary employed close to the antenna for MoM-FDTD-SGFDTD hybridisation. It depicts the advantage of using hybrid techniques due to their ability to analyse a system of multiple discrete regions by employing the principle of equivalent sources to excite the coupling surfaces. The method has been applied for modelling human body interaction with a short range RFID antenna to investigate and analyse the near field and far field radiation pattern for which the cumulative distribution function of antenna radiation efficiency is presented. The field distributions of the simulated structures show reasonable and stable results at 900 MHz. This method facilitates deeper investigation of the phenomena in the interaction between electromagnetic fields and human tissues.
Ministry of Higher Education Malaysia and Universiti Tun Hussein Onn Malaysia (UTHM)

APA, Harvard, Vancouver, ISO, and other styles

35

Ramli, Khairun Nidzam. "Modelling and analysis of complex electromagnetic problems using FDTD subgridding in hybrid computational methods : development of hybridised Method of Moments, Finite-Difference Time-Domain method and subgridded Finite-Difference Time-Domain method for precise computation of electromagnetic interaction with arbitrarily complex geometries." Thesis, University of Bradford, 2011. http://hdl.handle.net/10454/5443.

Full text

Abstract:

The main objective of this research is to model and analyse complex electromagnetic problems by means of a new hybridised computational technique combining the frequency domain Method of Moments (MoM), Finite-Difference Time-Domain (FDTD) method and a subgridded Finite-Difference Time-Domain (SGFDTD) method. This facilitates a significant advance in the ability to predict electromagnetic absorption in inhomogeneous, anisotropic and lossy dielectric materials irradiated by geometrically intricate sources. The Method of Moments modelling employed a two-dimensional electric surface patch integral formulation solved by independent linear basis function methods in the circumferential and axial directions of the antenna wires. A similar orthogonal basis function is used on the end surface and appropriate attachments with the wire surface are employed to satisfy the requirements of current continuity. The surface current distributions on structures which may include closely spaced parallel wires, such as dipoles, loops and helical antennas are computed. The results are found to be stable and showed good agreement with less comprehensive earlier work by others. The work also investigated the interaction between overhead high voltage transmission lines and underground utility pipelines using the FDTD technique for the whole structure, combined with a subgridding method at points of interest, particularly the pipeline. The induced fields above the pipeline are investigated and analysed. FDTD is based on the solution of Maxwell's equations in differential form. It is very useful for modelling complex, inhomogeneous structures. Problems arise when open-region geometries are modelled. However, the Perfectly Matched Layer (PML) concept has been employed to circumvent this difficulty. The establishment of edge elements has greatly improved the performance of this method and the computational burden due to huge numbers of time steps, in the order of tens of millions, has been eased to tens of thousands by employing quasi-static methods. This thesis also illustrates the principle of the equivalent surface boundary employed close to the antenna for MoM-FDTD-SGFDTD hybridisation. It depicts the advantage of using hybrid techniques due to their ability to analyse a system of multiple discrete regions by employing the principle of equivalent sources to excite the coupling surfaces. The method has been applied for modelling human body interaction with a short range RFID antenna to investigate and analyse the near field and far field radiation pattern for which the cumulative distribution function of antenna radiation efficiency is presented. The field distributions of the simulated structures show reasonable and stable results at 900 MHz. This method facilitates deeper investigation of the phenomena in the interaction between electromagnetic fields and human tissues.

APA, Harvard, Vancouver, ISO, and other styles

36

Hamdi, Maher. "Conception de tags d'identification sans puce dans le domaineTHz." Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENT048/document.

Full text

Abstract:

Ce travail de thèse a été réalisé dans le cadre d'un contrat avec l'ANR (ANR-09-VERS-013 « THID ») et porte sur le développement d'une nouvelle génération de tags Chipless à bas coûts fonctionnant dans le domaine THz, pour des applications d'identification et/ou authentification unitaire des articles commerciaux, des papiers d'identités, des personnes pour le contrôle d'accès... Les structures proposées, constituées d'un empilement périodique de couches diélectriques d'indices de réfraction différents, utilisent les propriétés particulières des cristaux photoniques 1D de présenter une réponse électromagnétique entrecoupée de bandes interdites photoniques (BIP). Toute perturbation de la périodicité de la structure engendre des pics dans les bandes interdites qui sont utilisés pour coder une information binaire. Cette structuration particulière des matériaux permet donc de manipuler précisément une signature électromagnétique. Pour des raisons liées à l'industrialisation (facilité de fabrication en masse) et aussi de coût, nous avons retenu des matériaux de base déjà couramment utilisés dans l'industrie papetière : le papier et le polyéthylène. Le choix de ces matériaux, qui doivent allier contraste d'indice élevé et faible absorption, représente une étape cruciale dans ce travail. Ainsi, à partir des résultats expérimentaux obtenus par spectroscopie THz dans le domaine temporel (THz-TDS) sur un grand nombre de matériaux, nous avons pu concevoir deux familles de tags sur la base de ces différents matériaux. Par ailleurs, nous avons développé deux méthodes de codage d'une information binaire, toutes deux basées sur l'absence ou la présence de pics dans une BIP, pics dont la position et le nombre dépendent bien évidemment des défauts de périodicité introduits. Pour des applications liées à l'identification, des capacités de codage de près de 20 bits ont été démontrées. Nous avons aussi montré que la richesse d'information contenue dans la réponse électromagnétique de ces Tags THz peut être utilisée pour les applications liées à l'authentification unitaire, en utilisant comme critère de discrimination le coefficient d'autocorrélation. Nous avons ainsi pu évaluer les performances d'un test d'authentification basé sur ce critère dans différents domaines d'analyse : temporel, fréquentiel et temps-fréquence. Nous avons montré qu'une étude du spectrogramme (combinant temps et fréquence) est ainsi bien plus pertinente qu'une étude dans les seuls domaines temporel ou fréquentiel
This thesis work deals with the development of a new generation of low-cost Chipless tags operating in the THz frequency domain, it has been supported by the french national agency for research (ANR-09-VERS-013 « THID » ). It covers a wide area of applications such as the identification and/or unitary authentication of commercial items, identity papers, access control…To manufacture these tags, we proposed to use a periodic stack of dielectric material layers with different refractive index and whose thickness is of the order of the wavelength, commonly known as a one dimensional photonic crystal. The electromagnetic signature of such a structure exhibits photonic bandgaps (PBG), i.e. frequency windows in which light propagation is prohibited. We suggested modifying the periodicity of the crystal to create defect levels (peaks) for example in the 1st PBG to encode binary information. This particular structure allows to precisely tuned an electromagnetic signature. To ensure a mass and cost effective industrialization, we retained basic materials which are widely used in the pulp and paper industry: paper and polyethylene. The choice of these materials, which must combine high index contrast and low absorption, represents the first and a crucial step in this work. We characterize a wide range of materials using classical THz time domain spectroscopy (THz-TDS) and we propose two families of tags based on paper and polyethylene. Furthermore, we developed two methods to encode binary information, both based on the absence or presence of peaks in a PBG, peaks whose number and position depend on the introduced defects of periodicity. In a real identification test, a coding capacity of nearly 20-bit has been demonstrated. We also showed that the information contained in the electromagnetic response of these THz tags can be used for other applications related to the unitary authentication and by using the correlation coefficient as criterion for discrimination of the different signatures. Therefore, we evaluate the performance of an authentication test based on this criterion in various analysis domains: time, frequency and time-frequency. We showed that a study of the spectrogram (combining time and frequency representation) is much more relevant than a study in the only time or frequency domain

APA, Harvard, Vancouver, ISO, and other styles

37

Naceur, Nahed. "Une méthode de décomposition de domaine pour la résolution numérique d’une équation non-linéaire." Electronic Thesis or Diss., Université de Lorraine, 2020. http://www.theses.fr/2020LORR0149.

Full text

Abstract:

Cette thèse porte sur l’analyse théorique et la résolution numérique d’un type d’équations semi-linéaires elliptiques et paraboliques. Ces équations sont souvent utilisées pour modéliser des phénomènes dans la dynamique de la population et les réactions chimiques. On a commencé cette thèse par l’étude théorique d’une équation elliptique semi-linéaire dont on a démontré l’existence d’une solution faible non négative sous des hypothèses plus générale que celles considérées dans des précédents travaux. Puis on a présenté une nouvelle méthode basée sur la méthode de Newton et la méthode de décomposition de domaine sans et avec recouvrement. Ensuite, on a rappelé quelques aspects théoriques concernant l’existence, l’unicité ainsi que la régularité de la solution d’une équation parabolique appelée équation de type Fujita. On a rappelé aussi des résultats sur l’existence de la solution globale et sur le temps maximal d’existence dans le cas d’explosion. Afin de calculer une approximation numérique de la solution de ce type d’équation, on a introduit une discrétisation en éléments finis dans la variable en espace et un schéma de Crank-Nicholson pour la discrétisation en temps. Pour résoudre le problème non linéaire discret on a implémenté une méthode de Newton couplée avec une méthode de décomposition de domaine. On a démontré que la méthode est bien posée. On a également traité un autre type d’équation parabolique dit équation de Chipot-Weissler. En premier, on a rappelé des résultats théoriques concernant cette équation. Puis, en se basant sur les méthodes numériques étudiées précédemment on a calculé une approximation numérique de la solution de cette équation. Dans la dernière section de chaque chapitre de cette thèse on a présenté des simulations numériques illustrant les performances des algorithmes étudiés et la cohérence des résultats avec la théorie
The subject of this thesis is to present a theoretical analysis and a numerical resolution of a type of quasi-linear elliptic and parabolic equations. These equations present an important role to model phenomena in population dynamics and chemical reactions. We started this thesis with the theoretical study of a quasi-linear elliptical equation for which we demonstrated the existence of a weak non-negative solution under more general hypotheses than those considered in previous works. Then we inspired a new method based on Newton’s method and the domain decomposition method without and with overlapping. Then, we recalled some theoretical aspects concerning the existence, the uniqueness and the regularity of the solution of a parabolic equation called Fujita equation. We also recalled results about the existence of the global solution and the maximum time of existence in the case of blow-up. In order to calculate a numerical approximation of the solution of this type of equation, we introduced a finite element discretization in the space variable and a Crank-Nicholson scheme for the time discretization. To solve the discrete nonlinear problem we implemented a Newton’s method coupled with a domain decomposition method. We have shown that the method is well posed. Another type of parabolic equation known as the Chipot-Weissler equation has also been treated. First, we recalled theoretical results concerning this equation. Then, based on the numerical methods studied previously, a numerical approximation of the solution of this equation was calculated. In the last section of each chapter of this thesis we presented numerical simulations illustrating the performance of the algorithms studied and its compatibility with the theory

APA, Harvard, Vancouver, ISO, and other styles

38

Beckstein, Pascal. "Methodenentwicklung zur Simulation von Strömungen mit freier Oberfläche unter dem Einfluss elektromagnetischer Wechselfelder." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2018. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-232474.

Full text

Abstract:

Im Bereich der industriellen Metallurgie und Kristallzüchtung treten bei zahlreichen Anwendungen, wo magnetische Wechselfelder zur induktiven Beeinflussung von leitfähigen Werkstoffen eingesetzt werden, auch Strömungen mit freier Oberfläche auf. Das Anwendungsspektrum reicht dabei vom einfachen Aufschmelzen eines Metalls in einem offenen Tiegel bis hin zur vollständigen Levitation. Auch der sogenannte RGS-Prozess, ein substratbasiertes Kristallisationsverfahren zur Herstellung siliziumbasierter Dünnschichtmaterialien, ist dafür ein Beispiel. Um bei solchen Prozessen die Interaktion von Magnetfeld und Strömung zu untersuchen, ist die numerische Simulationen ein wertvolles Hilfsmittel. Für beliebige dreidimensionale Probleme werden entsprechende Berechnungen bisher durch eine externe Kopplung kommerzieller Programme realisiert, die für Magnetfeld und Strömung jeweils unterschiedliche numerische Techniken nutzen. Diese Vorgehensweise ist jedoch im Allgemeinen mit unnötigem Rechenaufwand verbunden. In dieser Arbeit wird ein neu entwickelter Methodenapparat auf Basis der FVM vorgestellt, mit welchem sich diese Art von Berechnungen effizient durchführen lassen. Mit der Implementierung dieser Methoden in foam-extend, einer erweiterten Version der quelloffenen Software OpenFOAM, ist daraus ein leistungsfähiges Werkzeug in Form einer freien Simulationsplattform entstanden, welches sich durch einen modularen Aufbau leicht erweitern lässt. Mit dieser Plattform wurden in foam-extend auch erstmalig dreidimensionale Induktionsprozesse im Frequenzraum gelöst.

APA, Harvard, Vancouver, ISO, and other styles

39

Laurell, Hugo. "Time-frequency analysis of THz-time domain spectroscopy data." Thesis, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-357416.

Full text

Abstract:

This text investigates THz-TDS signals in the time-frequency domain. Addi- tionally this text discusses the prospects of using time-frequency analysis to alleviate distortion in THz spectrographic characterizations induced by back- reflections in the free space electro optic sampling used in the THz time-domain spectroscopy detection scheme. THz time domain spectroscopy is a technique for characterization of materials in the terahertz regime. The THz regime offers interesting properties of materials such as strong phonon-photon interaction and resonances for vibration states of molecules. Three time-frequency representations are compared for the analysis of the time-domain signal, the short-time Fourier transform, the Wigner-Ville transform and the continuous wavelet transform. It is concluded that the Wigner-Ville transform is most suited for analysis of the spectral properties of a single pulse due to the Wigner-Ville transforms inherit high spectral resolution. The continuous wavelet transform is most suited for analysis of the time-domain signal since it has no cross-term interference as compared to the Wigner-Ville transform. By masking the continuous wavelet transform with a Lorentzian time-frequency mask the back-reflections are dampened and the resolution of the characterization is improved.

APA, Harvard, Vancouver, ISO, and other styles

40

Ung, Benjamin Seam Yu. "Novel hardware for terahertz time-domain spectroscopy (THz-TDS)." Thesis, 2013. http://hdl.handle.net/2440/83737.

Full text

Abstract:

Terahertz time-domain spectroscopy (THz-TDS) systems have been generally limited to a single mode of operation, either in transmission or reflection geometries. The possibility of systems able to operate simultaneously in both geometries opens new possibilities for material characterisation. This Thesis designs and characterises a novel system able to simultaneously capture spectra from samples at normal incidence transmission and reflection. This enables materials that are opaque and/or partially reflective, as well as materials that exhibit non-unity values of permittivity and/or permeability to be thoroughly investigated. In addition to a dual geometry system, this Thesis presents two novel beam-splitters useable in the terahertz (THz) range of frequencies from 0.1 to 10 THz. Optical components in the THz frequency range have been limited, with ongoing developments being made to fabricate and characterise lenses, polarizers and waveguides, with beam-splitters that are polarization dependent. The presented original contributions include a low-cost beam-splitter fabricated from an ultra-thin polymer substrate and silver paint, and a novel beam-splitter fabricated from conductive polymers. These beam-splitters provide a near frequency and polarization independent response. An introductory background into THz-TDS along with generation and detection methods are also offered as part of this Thesis. Four auxiliary investigations are also described in the appendices: (i) a dual scanning THz-TDS system, to improve acquisition times, (ii) a mini investigation into food quality control using THz-TDS, (iii) an investigation into security applications for THz-TDS and (iv) second harmonic generation (SHG) using a β radiation damaged barium borate (BBO) crystal and a Ti:Sapphire laser.
Thesis (Ph.D.) -- University of Adelaide, School of Electrical and Electronic Engineering, 2013

APA, Harvard, Vancouver, ISO, and other styles

41

徐國謙. "Application of THz Time-domain Spectroscopic Technique in Powdered Samples." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/36433274888217928299.

Full text

Abstract:

碩士
國立清華大學
物理學系
91
We use mode-locked Ti:Sapphire Laser, wavelength 800nm, after being chirped pulse amplification and splitted, the power of per pulse is 12.8GW, pulse width 130fs, to pump insulated GaAs witch biased by DC voltage, and generate THz pulse with pulse width 5ps.We can get the time-domain spectroscopy of THz by electro-optic sampling. We let the THz signal pass through Ba2(Ti1-xSnx)9O20 x=0，0.024 sintered 4hrs and calculate the dielectric constant by effective-medium theory, and we compare the result with the dielectric constant at microwave range (4GHz). After that, we get several conclusions：1.The dielectric constants of the powdered samples are similar to sintered samples (about 39.5 and 38). 2.At the rage 0.1THz~0.6THz (besides 0.2TH), we also get the result that the Q values of x=0.024 are higher. 3.The power absorption coefficients of x=0 and 0.024 are different obviously, this may be caused by sintered or not. Application of THz Time-domain Spectroscopic Technique in Powdered Samples

APA, Harvard, Vancouver, ISO, and other styles

42

Hsu, chih-cheng, and 徐志塍. "THz time-domain spectroscopy studies of the dielectric properties of rare=earth gallium garnet." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/58059811965797321758.

Full text

Abstract:

碩士
國立臺灣海洋大學
光電科學研究所
95
Here we studied the dielectric properties of Re3Ga5O12 garnet ceramics by THz-TDS (terahertz time-domain spectroscopy) at the frequency range from 0.25 to 1.0THz , and the dielectric properties of Re3Ga5O12 (Re:Nd,Sm,Eu,and Dy)were investigated for good substrate materials in MICs (microwave integrated circuits). Re3Ga5O12 (Re:Nd,Sm,Eu,and Dy)sintered at 1450°C had a high quality factor (Qxf) range from 40 to 200 THz and a low dielectric constant of between 10.2 and 12.5 .Therefor , Re3Ga5O12 ceramics ,especially TiO2-added Sm3Ga5O12 ceramics are good candidates for advanced substrate materials in microwave integrated circuits application .

APA, Harvard, Vancouver, ISO, and other styles

43

Hoffmann, Matthias Clemens [Verfasser]. "Novel techniques in THz-time-domain-spectroscopy : a comprehensive study of technical improvements to THz-TDS / vorgelegt von Matthias Clemens Hoffmann." 2006. http://d-nb.info/980654246/34.

Full text

APA, Harvard, Vancouver, ISO, and other styles

44

Hoffmann, Matthias C. [Verfasser]. "Novel techniques in THz-time-domain-spectroscopy : a comprehensive study of technical improvements to THz-TDS / vorgelegt von Matthias Clemens Hoffmann." 2006. http://nbn-resolving.de/urn:nbn:de:bsz:25-opus-25334.

Full text

APA, Harvard, Vancouver, ISO, and other styles

45

Silva, Ana Miguel Ferreira de Oliveira e. "Construction and optimization of a time-domain broadband THz spectrometer and its application to the measurement of new broadband THz polarizers." Master's thesis, 2021. https://hdl.handle.net/10216/139125.

Full text

APA, Harvard, Vancouver, ISO, and other styles

46

Lin, Wei-Chen, and 林威呈. "A new approach for simultaneous characterization of the material's permittivity and permeability by THz time-domain spectroscopy." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/39400506040474816320.

Full text

APA, Harvard, Vancouver, ISO, and other styles

47

Ramli, Khairun N., Raed A. Abd-Alhameed, Chan H. See, James M. Noras, and Peter S. Excell. "Electromagnetic Field Computation for Power Transmission Lines Using Quasi-Static Sub-Gridding Finite-Difference Time-Domain Approach." 2015. http://hdl.handle.net/10454/8065.

Full text

Abstract:

Yes
A new approach of modelling the electromagnetic wave propagation and the penetration of small objects, are investigated and analysed. The travelling electromagnetic wave from source is simulated by time-dependent Maxwell's solutions. Subgridding technique is imposed at the point of interest for observing the electromagnetic field in high resolution. The computational burden caused by a large number of time steps has been parried by implementing the state of art of quasi-static approach. The induced electromagnetic fields near a buried pipeline runs parallel to a 400 kV power transmission lines are presented, and discussed.

APA, Harvard, Vancouver, ISO, and other styles

48

Walther, Markus [Verfasser]. "Modern spectroscopy on biological molecules : structure and bonding investigated by THz time-domain and transient phase-grating spectroscopy / vorgelegt von Markus Walther." 2004. http://d-nb.info/970191170/34.

Full text

APA, Harvard, Vancouver, ISO, and other styles

49

Fischer, Bernd Michael [Verfasser]. "Broadband THz time-domain spectroscopy of biomolecules : a comprehensive study of the dielectric properties of biomaterials in the far-infrared / vorgelegt von Bernd Michael Fischer." 2006. http://d-nb.info/98063623X/34.

Full text

APA, Harvard, Vancouver, ISO, and other styles

50

Fischer, Bernd-Michael [Verfasser]. "Broadband THz time-domain spectroscopy of biomolecules : a comprehensive study of the dielectric properties of biomaterials in the far-infrared / vorgelegt von Bernd Michael Fischer." 2006. http://nbn-resolving.de/urn:nbn:de:bsz:25-opus-23421.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Dissertations / Theses on the topic 'THz quasi time domain'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles