Huang, Shengyang. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2009. / Includes bibliographical references (leaves 100-108). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

Several novel optical devices, which were designed to manipulate terahertz waves for broadband near-field imaging, wave-guiding (invisible space), and sensing (resonator), are presented in this thesis. We developed the original working concepts of each device, and demonstrated the prototype experimentally in our lab. The working concepts of physics were investigated in experiment, in simulation and in theoretical analysis. We exploited a tapered parallel-plate waveguide (PPWG) as a novel probe for broadband near-field imaging. This imaging probe consists of two metal plates with the plate spacing gradually tapered from one end to the other. We proved that the space tapering enables this probe to propagate the broadband THz waves efficiently (with low-loss, no cut-off and nearly no dispersion) from the input end of large spacing into the narrow end of sub-wavelength spacing. Working in a reflection mode, this imaging probe is proved to be able to differentiate the dielectric features as well as topographic information on the sample. Combined with the methodology of filtered back projection, we reconstructed a two-dimensional image of a gold pattern on a GaAs chip by using this tapered PPWG probe. The smallest feature of ~100 µm is resolved by using the waves with average wavelength of 1.5 mm. We studied the phenomenon of surface plasmon-polariton in THz range on the platform of a parallel-plate waveguide (PPWG). In this thesis, we show the characterization of the waveguide mode of a finite-width parallel plate waveguide by using an improved scattering-probe technique. An abrupt waveguide mode transition was observed at a very narrow frequency range. We demonstrated that this transition frequency is determined by the material properties of the waveguide, the frequencies of the electromagnetic waves as well as the geometry of the waveguide. This result provides a good guidance for the waveguide design for THz transmission. We also exploited the capability of using the spoof surface plasmon to enhance the reflectivity of an interface between free space and a PPWG. We demonstrated that the reflection coefficient of this interface can be enhanced up to ~100 % at a designed frequency, by cutting a designed pattern of periodic rectangular groove on the output facet of the PPWG. A lateral shift and a phase shift of the reflected beam is observed in the experiment, which is a strong reminiscent of Goos-Hanchen shift. We carried out the experimental, simulation and theoretical characterizations of the lateral and phase shift. As an application, we designed and demonstrated a prototype of a band-pass THz resonator. We introduced the concept of a waveguide-based two-dimensional inhomogeneous artificial dielectric into THz range. This artificial dielectric is the space between the two metal plates of a PPWG working in TE1 mode. We designed a THz mirage device (or an invisible space device) by using ray-tracing and full-wave simulations, which contributed to the first experimental demonstration of such a device. A metal coin of size several times larger than the working wavelength can be hidden in the device without casting any shadow. This work is in collaboration with Dr. Rajind Mendis and the author of this thesis contributed to the design and characterization of the device in simulations.

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.

Thesis (MSc)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Terahertz radiation is currently used in security, information and communication technology (ICT), and biomedical sciences among others. The usability of terahertz (THz) radiation, in many of its applications depends on characteristics of the materials being investigated in the THz range. At the heart of THz usage is a THz spectroscopy system necessary for the generation and detection of the THz radiation. In this thesis, we characterise such a THz spectroscopy system. In our typical THz spectrometric system, we make use of femtosecond (fs) laser technology and pump-probe principles for emission and detection of THz radiation. Background about the principles of generation THz radiation using fs triggered antennas and the principles of the spectroscopy technique and appropriate literature references are presented. Using an assembled commercially available kit, we reproduce known spectra in order to confirm correct functionality (for calibration) of the assembled spectroscopy system and to gain experience in interpreting these spectra. By introducing a suitable x - y scanning device we construct a crude THz imaging device to illustrate the principle. / AFRIKAANSE OPSOMMING: Terahertsstraling word deesdae wyd in die sekuriteits, inligting-en-kommunikasie en biomediese sektore aangewend. Die gepastheid van terahertsstraling (THz) vir ’n spesifieke toepassings hang af van die eienskappe van die materiale wat ondersoek word. Vir die uitvoer van sulke eksperimente word ’n THz-spektroskopie sisteem benodig vir die opwekking en meting van THz-straling. In hierdie tesis word so ’n THz-spektroskopie sisteem beskou en gekarakteriseer. In die sisteem word van ’n femtosekondelaser (fs) gebruik gemaak in ’nn pomp-en-proef opstelling vir die uitstraling en meting van THz-straling. Die beginsels rakende die opwekking van THz-straling, deur gebruik te maak van ’n antenna wat deur ’n fs-laser geskakel word, asook die beginsels van die spektroskopiese tegniek, met toepaslike verwysings, word in die tesis aangebied. Deur gebruik te maak van’n kommersiële THz opstelling is bekende spektra gemeet om die korrekte funksionering (vir kalibrasie doeleindes) na te gaan en om ondervinding op te doen in die interpretasie van hierdie spektra. ’n X-Y-translasie toestel is tot die opstelling bygevoeg om THz-afbeelding moontlik te maak en sodoende hierdie beginsel te illustreer.

Sy, Ming Yiu. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (p. 95-100). / Abstracts in English and Chinese. / Abstract --- p.1 / Acknowledgments --- p.5 / List of figures --- p.9 / List of tables --- p.13 / List of abbreviations --- p.14 / List of publications and awards --- p.15 / Awards --- p.16 / Chapter Chapter 1 --- Introduction --- p.17 / Chapter 1.1 --- Terahertz radiation --- p.18 / Chapter 1.1.1 --- Terahertz sources --- p.19 / Chapter 1.1.2 --- Terahertz systems --- p.20 / Chapter 1.1.3 --- Reflection and Transmission geometries --- p.21 / Chapter 1.2 --- Terahertz biomedical applications --- p.24 / Chapter 1.2.1 --- Biomolecules --- p.24 / Chapter 1.2.2 --- THz biomedical imaging --- p.25 / Chapter 1.2.3 --- THz Spectroscopy --- p.26 / Chapter 1.3 --- Objectives --- p.26 / Chapter 1.4 --- Structure of this thesis --- p.26 / Chapter Chapter 2 --- Theory and experimental system --- p.28 / Chapter 2.1 --- Theory --- p.28 / Chapter 2.1.1 --- Propagation of electromagnetic field through dielectric media --- p.29 / Chapter 2.1.2 --- A de-noising method --- p.32 / Chapter 2.1.3 --- Baseline calculation --- p.34 / Chapter 2.1.4 --- Frequency-dependent Refractive Index and Absorption Coefficient.. --- p.37 / Chapter 2.2 --- Experimental Configuration --- p.41 / Chapter 2.2.1 --- Terahertz generation and detection --- p.41 / Chapter 2.2.2 --- Configuration of our system --- p.44 / Chapter 2.2.3 --- Hand-held TPI Setup --- p.46 / Chapter 2.3 --- Data Structure --- p.48 / Chapter 2.4 --- Pre-processing and the user interface --- p.49 / Chapter 2.4.1 --- Data pre-processing 1 (Chopping) --- p.49 / Chapter 2.4.2 --- Data pre-processing 2 (Angle selection) --- p.50 / Chapter 2.4.3 --- The user interface for the data processing --- p.52 / Chapter Chapter 3 --- Ex-v/vo experiment: investigating the origin of contrast --- p.54 / Chapter 3.1 --- Liver Cirrhosis --- p.54 / Chapter 3.1.1 --- Liver --- p.54 / Chapter 3.1.2 --- Liver cirrhosis --- p.54 / Chapter 3.1.3 --- The trend of liver cirrhosis --- p.56 / Chapter 3.1.4 --- Technique for diagnosing liver cirrhosis --- p.57 / Chapter 3.2 --- Experiment protocol --- p.58 / Chapter 3.2.1 --- Formalin fixing --- p.58 / Chapter 3.2.2 --- Sample preparation --- p.58 / Chapter 3.2.3 --- Formalin fixing protocol --- p.60 / Chapter 3.2.4 --- Histopathology --- p.61 / Chapter 3.2.5 --- Protocol for measuring sample water content --- p.61 / Chapter 3.3 --- Results and discussion --- p.62 / Chapter 3.3.1 --- Optical parameters of the fresh and fixed samples --- p.62 / Chapter 3.3.2 --- Consistency with previous results --- p.63 / Chapter 3.3.3 --- The relationship between water content and optical parameters --- p.64 / Chapter 3.3.4 --- Conclusion --- p.68 / Chapter Chapter 4 --- In-vivo experiment: imaging of human skin --- p.69 / Chapter 4.1 --- Human skin --- p.69 / Chapter 4.1.1 --- The structure of human skin --- p.69 / Chapter 4.1.2 --- Skin thickness --- p.70 / Chapter 4.1.3 --- The structure and regeneration of stratum corneum --- p.70 / Chapter 4.1.4 --- Stratum corneum related Skin disease --- p.72 / Chapter 4.2 --- Combing reflections of electromagnetic wave --- p.73 / Chapter 4.3 --- Experiment protocol --- p.74 / Chapter 4.3.1 --- THz response of human skin --- p.74 / Chapter 4.3.2 --- Protocol for measuring human skin --- p.75 / Chapter 4.4 --- Results and discussion --- p.76 / Chapter 4.4.1 --- The variation due to the position --- p.76 / Chapter 4.4.2 --- The variation due to the temperature and humidity --- p.78 / Chapter 4.4.3 --- Discussion --- p.79 / Chapter Chapter 5 --- Noise evaluation --- p.80 / Chapter 5.1 --- The main noise source --- p.80 / Chapter 5.2 --- SNR and DR --- p.80 / Chapter 5.2.1 --- Signal to noise ratio (SNR) --- p.80 / Chapter 5.2.2 --- Dynamic range (DR) --- p.81 / Chapter 5.2.3 --- SNRVS DR --- p.82 / Chapter 5.3 --- Simulation of noise impact on the complex refractive index --- p.83 / Chapter 5.3.1 --- Methodology --- p.83 / Chapter 5.3.2 --- SNR: Simulation results and discussions --- p.85 / Chapter 5.3.3 --- DR: Simulation results and discussions --- p.87 / Chapter 5.3.4 --- Conclusion --- p.89 / Chapter Chapter 6 --- Conclusion and future work --- p.90 / Chapter 6.1 --- Conclusion --- p.90 / Chapter 6.1.1 --- A summary of Terahertz pulsed imaging (TPI) techniques --- p.90 / Chapter 6.1.2 --- Our system and calculations --- p.90 / Chapter 6.1.3 --- Terahertz spectroscopy of liver cirrhosis: investigating the origin of contrast --- p.91 / Chapter 6.1.4 --- In-v/vo study: skin measurement --- p.91 / Chapter 6.1.5 --- SNR sensitivity --- p.92 / Chapter 6.2 --- Suggestions for future work --- p.92 / Chapter 6.2.1 --- Algorithms --- p.92 / Chapter 6.2.2 --- Understanding the origin of contrast --- p.93 / Chapter 6.2.3 --- Application in cardiovascular diagnosing imaging --- p.93 / Chapter 6.3 --- Concluding remarks --- p.94 / References --- p.95

Kan, Wai Chi. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references (p. 111-116). / Abstract --- p.i / Acknowledgement --- p.iii / List of Publications --- p.vi / List of Figures --- p.xi / List of Tables --- p.xii / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Terahertz Radiation --- p.1 / Chapter 1.2 --- Biomedical Applications of Terahertz Imaging --- p.3 / Chapter 1.3 --- THz Spectroscopy --- p.4 / Chapter 1.4 --- Osteoarthritis --- p.4 / Chapter 1.5 --- Aim and motivation --- p.5 / Chapter 1.6 --- Overview of thesis --- p.5 / Chapter 2 --- Theory --- p.7 / Chapter 2.1 --- Propagation of electromagnetic field through dielectric media --- p.7 / Chapter 2.2 --- Deconvolution --- p.10 / Chapter 2.3 --- Baseline offset --- p.12 / Chapter 2.4 --- Frequency-dependent Refractive Index and Absorption Coefficient --- p.15 / Chapter 2.4.1 --- Reflection Geometry --- p.15 / Chapter 2.4.2 --- Transmission Geometry --- p.17 / Chapter 2.5 --- Conversion of Optical Delay into Depth --- p.22 / Chapter 2.6 --- Finite Difference Time Domain Method --- p.23 / Chapter 2.7 --- Summary --- p.25 / Chapter 3 --- Terahertz Systems --- p.26 / Chapter 3.1 --- Terahertz Pulsed Generation --- p.26 / Chapter 3.2 --- Terahertz Pulsed Detection --- p.28 / Chapter 3.3 --- Terahertz Pulsed Imaging (TPI) System --- p.29 / Chapter 3.4 --- Reflection System --- p.29 / Chapter 3.4.1 --- Flatbed System --- p.29 / Chapter 3.4.2 --- Probe --- p.32 / Chapter 3.5 --- Transmission System --- p.36 / Chapter 3.5.1 --- Antenna --- p.39 / Chapter 3.6 --- Data Acquisition --- p.40 / Chapter 3.6.1 --- Flatbed System --- p.40 / Chapter 3.6.2 --- Probe --- p.42 / Chapter 3.7 --- Baseline Validation --- p.46 / Chapter 4 --- Osteoarthritis --- p.48 / Chapter 4.1 --- Introduction --- p.48 / Chapter 4.2 --- Cartilage Composition and Structure --- p.49 / Chapter 4.3 --- 〇A symptoms --- p.51 / Chapter 4.4 --- Other Imaging Techniques --- p.52 / Chapter 4.5 --- Sample Preparation and Histology --- p.54 / Chapter 5 --- THz Pulsed Imaging of OA --- p.58 / Chapter 5.1 --- Results --- p.58 / Chapter 5.1.1 --- Optical Delays --- p.59 / Chapter 5.1.2 --- Estimation of surface refractive index --- p.69 / Chapter 5.1.3 --- Conversion of Optical Delay into Cartilage Thickness --- p.72 / Chapter 5.1.4 --- Correlation with Histology --- p.74 / Chapter 5.1.5 --- Errors and Problems --- p.80 / Chapter 5.2 --- FDTD of cartilage layers --- p.85 / Chapter 5.3 --- Conclusion --- p.87 / Chapter 6 --- Sliced Cartilage Sample and Bone Measurement --- p.88 / Chapter 6.1 --- Sliced Cartilage Samples --- p.88 / Chapter 6.1.1 --- Multi-reflections of sliced cartilage samples --- p.89 / Chapter 6.1.2 --- The influence of pressure on cartilage thickness --- p.91 / Chapter 6.1.3 --- Estimation of surface refractive index of sliced cartilage samples --- p.93 / Chapter 6.1.4 --- Comparison between sliced cartilage and knee joint measurements --- p.95 / Chapter 6.2 --- Bone --- p.97 / Chapter 7 --- Transmission System Result --- p.99 / Chapter 7.1 --- Data Validation --- p.99 / Chapter 7.1.1 --- Water spectrum --- p.99 / Chapter 7.1.2 --- Quartz measurement --- p.100 / Chapter 7.2 --- Liquid cell --- p.100 / Chapter 7.3 --- Cartilage Transmission Result --- p.103 / Chapter 7.4 --- Difficulties and problems --- p.105 / Chapter 7.5 --- Conclusions --- p.106 / Chapter 8 --- Conclusions and future work --- p.107 / Chapter 8.1 --- Summary --- p.107 / Chapter 8.2 --- Discussion --- p.107 / Chapter 8.3 --- Suggestions for further study --- p.109 / Bibliography --- p.111

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Les Lasers à Cascade Quantique (QCL) sont de "nouvelles" sources THz dont les progrès en termes de puissance, température de fonctionnement et qualité de faisceau sont remarquables. Les QCL sont utilisés dans des dispositifs d'imagerie THz continue pour le Contrôle Non Destructif de matériaux. Une première application de CND sur des matériaux composites permet de mettre en évidence de manière qualitative les défauts d'imprégnation des fibres par la résine ou les dommages causés par un impact. Des images à 3,8 THz, en transmission et ré flexion, ont pu être comparées avec une technique de CND par ultrasons. Une seconde application quantitative porte sur la concentration d'eau dans deux matériaux polymères à tendance hydrophobe : le polystyrène et le polypropylène. L'établissement d'une relation entre la transmittance de l'échantillon et sa prise de masse d'eau permet d'établir une cartographie quantifiée de la concentration d'eau. Ces cartographies sont nécessaires à la connaissance du processus de diffusion de l'eau dans les matériaux polymères. / Quantum Cascade Lasers (QCL) are "new" THz sources that have enjoyed remarkable progress in terms of power, operating temperature and beam quality. QCLs are used in continuous wave THz imaging setups applied to Non Destructive Testing of materials. A first qualitative application of NDT allows us to highlight defects in the fibers impregnation by resin or damages caused by an impact on composite materials. Transmission and reflection images at 3.8 THz are compared with a NDT ultrasonic technique. A second quantitative application relates to the water concentration in two hydrophobic polymeric materials: polystyrene and polypropylene. Establishing a relationship between the transmittance of the sample and mass water content enables us to draw up a quantified mapping of the latter. These maps are necessary for the understanding of the water diffusion process in polymeric materials.

Le but de cette thèse est d’établir une modélisation électromagnétique du détecteurbolométrique térahertz (THz). Ce travail aide à faciliter la conception de bolomètre THz dontla structure est basée sur celle de bolomètre infrarouge à température ambiante. Le contextede la thèse est l’imagerie THz active. Nous avons étudié le comportement électromagnétiqued’un bolomètre à antenne de bande spectrale 1 – 5 THz. Deux modes de simulation ont étéréalisées : l’une est en mode de réception et l’autre est d’émission. La combinaison de cesmodes de simulation constitue un outil important pour concevoir le bolomètre THz. Latechnique de spectroscopie par transformée de Fourier a été utilisée pour caractériserexpérimentalement le comportement électromagnétique du détecteur. Nous avons mesuré laréflectivité de la surface du plan focal de détecteur ainsi que la réponse spectrale du détecteur.Les deux sont confrontées avec la simulation et elles se trouvent en bon accord. Avec lesconnaissances obtenues des résultats théorique et mesuré, la recherche aide à améliorer desperformances du détecteur actuel. Nous avons aussi proposé un design pour le bolomètre defaible fréquence (850 GHz). Ce dernier ouvre la perspective d’emmener la technologie debolomètre d’infrarouge vers la bande sous-térahertz où l’imagerie est beaucoup plusfavorable. / This PhD thesis aims to establish an electromagnetic modeling of the bolometer atterahertz (THz) range that can facilitate the design of the detector from the uncooled infraredbolometer technology. The envisaged application for the detectors lies in active THz imagingat room temperature. We have studied the optical coupling of a THz antenna-coupledbolometer operating in the range 1 – 5 THz. Simulations in receiving and transmitting modeshave been performed to study the optical characteristics of the bolometer. The combination ofthese two simulation types leads to a powerful toolset to design terahertz bolometers. For theexperimental aspect, measurements have been performed by using Fourier-transformtechnique to study experimentally the electromagnetic behavior of the bolometer. They aremeasurement of reflectivity of the focal plane array’s surface and spectral responsemeasurement. The results of measurement were found to be in good agreement with thesimulation. The understanding from the study in this PhD helps us make improvement to theactual detector. Also the design of bolometer for low frequency (850 GHz) has beenproposed. This leads to a perspective of using bolometer for terahertz imaging at thefrequency where many characteristic of the terahertz radiation are favorable for imagingapplication.