Дисертації з теми "Heterodyne effect"

Le principe consiste à moduler, non pas la source lumineuse, mais le faisceau lui-même. On réalise ensuite un hétérodynage optique entre le faisceau module et une partie non modulée de ce faisceau, prise comme référence. Transmission des deux faisceaux par fibre optique à une photodiode connectée directement à l'entrée d'un récepteur de télévision. Réalisation d'une transmission de trois canaux de télévision par une fibre optique

L'objectif de ce travail est d'étudier l'impact d'un traitement « physique » sur la formation d'un dépôt minéral dans un échangeur de chaleur. Plus particulièrement, on s'intéressera à l'effet des ondes ultrasoniques, ainsi qu'à l'effet d'un traitement électromagnétique. Pour mener à bien cette étude, un pilote expérimental a été mis en place afin de tester ces traitements sur deux types d'échangeur de chaleur, un échangeur à plaques et joints et un échangeur platulaire. Plusieurs paramètres de fonctionnement tels que le débit, la durée et la température ont été testés expérimentalement, afin d'identifier leur influence sur la précipitation du carbonate de calcium et la formation de tartre dans l'échangeur. Pour mettre en évidence l'efficacité des traitements cités, une comparaison a ensuite été réalisée entre des expériences sans aucun traitement et des expériences avec un traitement physique, en utilisant une eau de réseau avec un léger pouvoir entartrant. La solubilité inverse du carbonate de calcium et le chauffage de l'eau dans l'échangeur initient la précipitation du carbonate de calcium dans l'eau ainsi que sur les parois de l'échangeur en contact avec cette eau. Les traitements physiques testés sont le traitement ultrasonique à deux fréquences différentes, le traitement électromagnétique de basse fréquence et de faible intensité, et le couplage traitements ultrasonique et électromagnétique. La première partie de ces travaux s'est portée sur une modélisation numérique, l'une avec Phreeqc interactive pour identifier les phases cristallisées et l'autre avec Comsol Multiphysique 6.0 pour identifier les zones de l'échangeur les plus sensibles à la formation du dépôt. Cela permettra notamment de positionner de façon optimale le dispositif ultrasonique, et de modéliser la dispersion des ondes ultrasoniques dans l'échangeur. Les résultats de l'analyse numérique obtenue par ces modèles ont ensuite été comparés aux mesures expérimentales. Les expériences réalisées permettent de quantifier le dépôt dans l'échangeur (via la dissolution de celui-ci dans une solution d'acide nitrique et le dosage du calcium à l'ICP), ou de qualifier ce dépôt (via un démontage de l'échangeur et des observations du dépôt au microscope). Les résultats obtenus montrent que le traitement ultrasonique permet de réduire d'environ 65% le dépôt, tandis que l'efficacité du champ électromagnétique est de l'ordre de 75%. Le couplage des deux traitements n'est pas bénéfique. A l'heure actuelle, tous les traitements physiques testés permettent une réduction de la quantité de tartre déposé, mais n'empêchent pas la formation du dépôt. Ces traitements n'affectent pas le polymorphisme du carbonate de calcium : dans tous les cas, le dépôt analysé est de la calcite. D'un point de vue industriel, ces traitements permettront de maintenir plus longtemps un bon transfert thermique et de réduire la fréquence de maintenance des échangeurs
In order to study the impact of the heterodyne effect on the formation of mineral deposits from domestic water networks in a heat exchanger, an experimental pilot was set up to test this technology on two types of heat exchangers, plate and joint exchanger and platelet exchanger. Several operating parameters such as flow rate, time, and temperature were experimentally tested in order to identify their influence on calcium carbonate precipitation and scale formation in the exchanger. In order to approve the efficiency of the heterodyne effect, a comparison was made with other physical treatments that were tested on the same pilot, namely: ultrasonic treatment at two different frequencies, low frequency, and low-intensity electromagnetic treatment, and the ultrasonic-electromagnetic coupling. The first part of this work focused on numerical modeling, two software were used, Phreeqc interactive and COMSOL Multiphysics 6.0. On the one hand identify the nature of crystallized polymorphism, whether at the pilot-scale or at the industrial scale. And on the other hand to identify the sensitive areas for the formation of the deposit in order to know the location of the ultrasonic system, and to model the dispersion of the ultrasonic waves at different frequencies and power, either in the water or in the metallic surfaces of the exchanger. The results of the numerical analysis obtained by these models were then compared to the experimental measurements.A series of laboratory-scale experiments, with or without the physical treatment, is performed on an exchanger that has been insulated from the outside with an insulating cover and equipped with thermocouples in order to evaluate the impact of the physical treatment tested on the heat transfer. 100 Liters of water with a scaling capacity (30°F) was heated to 50°C within the exchanger for 72 hours in a closed circuit. Due to the high content of dissolved calcium carbonate and the decrease of its solubility when the temperature increases, a precipitate of calcium carbonate forms inside the heat exchanger, but also in the water, as well as on the walls of the exchanger. At the end of each experiment, the deposit is dissolved in 5% (vol.) nitric acid and analyzed by ICP-AES spectroscopy to perform a complete material balance and determine the amount of scale precipitated on the exchanger plates. A dismantling of the exchanger was carried out in each type of test in order to analyze the distribution of the deposit in the whole of the plates by 3D digital microscopy and confocal microscopy, to analyze the precipitated polymorphism by RAMAN spectroscopy and scanning electron microscopy, and the size distribution of the precipitated particles by laser granulometry. The results obtained show that the heterodyne-guided waves allow reducing 65,46% of the deposit. On the other hand, the treatment that allows better reduction is the electromagnetic treatment with a percentage of reduction of 76,83%, without changing the nature of polymorphism. At present, all the physical treatments tested allow a reduction in the amount deposited, but do not prevent the total formation of the deposit. These methods aim to minimize the occurrence of fouling. They are preventive rather than corrective methods

Cette thèse porte sur la fabrication et la caractérisation d'un mélangeur hétérodyne, à partir d'YBa2Cu3O7, un matériau supraconducteur à haute température critique. Nous avons évalué son potentiel pour la détection d'ondes térahertz. La physique complexe des jonctions irradiées a été correctement décrite en modifiant légèrement les équations quasi-classiques d'Usadel, originellement développées pour les supraconducteurs inhomogènes à basse température critique. Les mesures de transport électronique ont montré que nos dispositifs respectent le modèle de la jonction résistivement shuntée. Nous avons expliqué leur fonctionnement à haute fréquence au moyen du modèle à trois ports, et démontré la détection d'ondes jusqu'à 400 GHz. Nous avons identifié l'efficacité de conversion du mélange hétérodyne comme le produit de trois termes : deux rendent compte des adaptations d'impédances en entrée et sortie du mélangeur, le troisième caractérise la conversion à basse fréquence des signaux térahertz. La puissance de l'oscillateur local nécessaire, l'étendue dynamique du mélangeur ainsi que son efficacité de conversion ont été mesurées, s'accordant bien avec les simulations numériques. Le recours à un réseau de jonctions Josephson synchronisées est incontournable pour parvenir à créer un oscillateur local puissant et spectralement fin à partir de l'oscillation propre des jonctions. Nous avons identifié le verrouillage par une boucle externe comme l'unique mécanisme efficace de synchronisation et simulé son effet. Enfin nous avons mesuré la première signature d'une synchronisation dans un réseau à deux dimensions de jonctions irradiées
In this thesis, we used a high-Tc superconducting material, YBa2Cu3O7, to make a heterodyne mixer. We aimed at evaluating its ability for terahertz detection. We also worked towards the fabrication of an on-chip local oscillator, designed with an array of Josephson junctions. The originality of this study stems from a unique way of engineering Josephson junctions, based on ion irradiation. We described the complex physics of ion irradiated Josephson junctions through a modified version of quasi-classical Usadel equations, which have originally been derived for non-homogenous low-Tc superconductivity. The d-c electronic transport measurements showed that our irradiated Josephson junctions are well described by the resistively shunted junction model. Furthermore, we explained the high-frequency mixing operations with the three-port model, and proved the heterodyne detection of signals up to 400 GHz. We identified the heterodyne conversion efficiency as a product of three terms: two depending on impedance mismatches and the third one characterizing the intrinsic down-conversion ability of the Josephson junction. The dynamic range of the mixer, its conversion efficiency and its dependence on local oscillator power were measured and found to be in agreement with simulations. An array of synchronized junctions is necessary to create a powerful and spectrally pure local oscillator from Josephson oscillations. We identified the external locking as the only efficient mechanism to synchronize YBa2Cu3O7 irradiated junctions, showing its effect in simulated systems. We also reported a first evidence of synchronization in a two dimensional array of irradiated Josephson junctions

In the quest for ultrathin materials compatible with CMOS technology for all-optical signal processing applications in integrated photonics, graphene appears to be a promising candidate, with broadband1 optical properties and a high and broadband optical nonlinearity. However, researchers do not agree on the value of its nonlinear refractive index, and commonly used characterization methods do not provide a clear picture of the optical nonlinearity, in terms of its tensor nature or relaxation time. In the first part of this thesis, apart from the previously used Z-scan method, we have also used the ultrafast Optical Kerr Effect method coupled to Optical Heterodyne Detection (OHD-OKE) for the characterization of the third order optical nonlinearity of monolayer CVD graphene at telecom wavelengths. This method allows to separately measure the real and the imaginary part of the third-order nonlinearity, as well as their dynamics. With respect to the Z-scan method, OHD-OKE presents the major advantage of being robust against inhomogeneities of the sample. As such, we have demonstrated that graphene has a negative nonlinear refractive index, contrary to previously reported results. In addition, we have studied the real and imaginary part of graphene’s nonlinearity, when electrostatic gating is applied to change the chemical potential of graphene. Furthermore, we have proposed an enhanced version of the OHD-OKE method, together with the appropriate theoretical framework, in order to extract the tensor elements of the nonlinearity including the out-of-plane tensor elements. In particular, we have measured separately the time response of the two main tensor elements of the nonlinear susceptibility and we have experimentally verified that the out-of-plane tensor components are negligible. In the second part of this thesis, we have investigated, from an experimental point of view, the use of the nonlinear optical response of graphene for all-optical switching applications in integrated photonics. Namely, we have designed simple silicon nitride waveguide structures that constitute basic building blocks of switching devices, which were then fabricated and covered by graphene patches. Finally, we have experimentally tested the graphene-covered structures at low and high power levels and discussed the results.
Doctorat en Sciences de l'ingénieur et technologie
info:eu-repo/semantics/nonPublished

Laser spectroscopic techniques have, during the last decades, demonstrated an extraordinary capability for sensitive detection of molecular constituents in gas phase. Since spectra from such techniques constitute unique and characteristic signatures for each type of species, these techniques enable investigations of molecular structures as well as detection of the presence of species in a gas mixture. They are therefore used for a variety of application, from fundamental studies to the assessment of gas concentrations. In fact, quantitative assessments of gas concentrations by laser-based techniques are constantly gaining in popularity, primarily due to properties such as high sensitivity and selectivity and an ability to perform non-invasive measurement. Moreover, investigations of isolated molecular transitions under different conditions provide excellent means to obtain a comprehensive understanding of spectral broadening mechanisms, which is of importance for, for example, environmental sciences and remote sensing applications. In fundamental studies, spectroscopic parameters are often retrieved from fits of a model function of the technique used, which in turn is based upon a suitable lineshape function. In order to obtain parameter values with highest possible accuracy, it is of importance to use the lineshape model that most correctly can predict the measured spectra. Even though the Voigt function is the most commonly used lineshape model when both Doppler and collision broadenings are present, it is not always suitable when spectroscopic parameters are to be assessed with high precision. This thesis represents a thorough investigation of Dicke narrowing and speed-dependent effects, which are phenomena that are not accounted for by the conventional Voigt profile. For the first time, it is demonstrated that both these effects take place not only in absorption but also in the dispersion mode of detection. Their dispersion lineshape functions are first theoretically presumed and explicitly given before they are validated experimentally by the noise-immune cavity-enhanced optical heterodyne molecular spectrometry (NICE-OHMS). By using the models developed, it is also shown that although the two modes of detection, absorption and dispersion, both can provide good quality of fits, they do not always provide identical spectroscopic parameters. A detailed analysis under which conditions they do so, and subsequent recommendations of their use, are presented. It also describes the instrumental implementation of a distributed-feed-back (DFB) laser-based NICE-OHMS instrumentation, which constitutes an important step towards the further development of this technique. Due to the wide tunability of the DFB laser, the setup is capable of extending the working range of NICE-OHMS into the collision broadening region, which, in turn, allows for precise spectroscopic studies. The use of a fiber-coupled DFB laser also provides a compact NICE-OHMS system. The minimum detectable on-resonance absorption was assessed to 2× 10-10 cm-1 for a 70 s integration time.

The present work would like contribute to the research in this area, by offering some results on the optical properties, disorder and non-linear effects on wave propagation in semiconductor-based two-dimensional photonic crystal waveguides. The aim is to lead the reader from the basic concepts of photonic crystals (Chapter 1), up to the properties of a 2D photonic crystal (Chapter 2) and the defect line induced waveguide in a 2D photonic crystal (Chapter 3). The propagation properties, the unusual dispersion relation, and the particular regime, known as Slow Light regime, will be analyzed depthly. Particular attention is devoted to model the extrinsic disorder induced by the fabrication process and its impact on the propagation properties of the waveguide (Chapter 4). In the last two chapters, the focus will be on two techniques to characterize photonic crystal waveguides. The first tool is the Time-Wavelength Reflectance Map (Chapter 5), developed with Thales Research and Technology, Paris, France, that permits to evaluate the propagation properties of the waveguide as function of the wavelength showing us a deep physical insight for understanding the role of disorder induced scattering and how it is connected to dispersion. In Chapter 6, a laboratory setup will be presented, based on the Heterodyne Pump-Probe technique, used in a set of experiments at DTU Fotonik, with the main objective to investigate on the Slow Light regime.
Questo lavoro di tesi presenta alcuni nuovi risultati sulle proprietà ottiche e sugli effetti del disordine sulla propagazione in guide d'onda a cristallo fotonico bidimensionale. Lo studio parte dai concetti di base dei cristalli fotonici (Cap. 1), quali la loro struttura a bande, fondamentali per comprendere appieno le proprietà dei cristalli fotonici bidimensionali (Cap. 2). Nel Cap. 3 sono approfondite le proprietà di propagazione della luce nelle guide d'onda realizzate in cristalli bidimensionali, in particolare la loro tipica relazione di dispersione e il regime di propagazione noto come regime di Luce Lenta (Slow Light regime). Nello stesso capitolo, si introduce, inoltre, un modello teorico per il Four-Wave Mixing, fenomeno non lineare solo recentemente osservato in questo tipo di guide. Il Cap. 4 introduce brevemente i processi di fabbricazione per questi dispositivi; vengono quindi discussi i punti critici di tali processi, modellizzati come disordine estrinseco, e l'impatto che questi hanno sulle proprietà di propagazione della guida. Gli ultimi due capitoli sono relativi alla parte sperimentale di questo lavoro. Sono state infatti studiate due tecniche per la caratterizzazione delle guide d'onda a cristallo fotonico. La prima è la mappa di riflettanza tempo-lunghezza d'onda (Cap. 5), sviluppato presso Thales Research and Technology (Paris, France), che permette di valutare le proprietà di propagazione della guida in funzione della lunghezza d'onda e l'impatto della dispersione indotta dal disordine estrinseco della guida. La seconda è la tecnica Heterodyne Pump-Probe, utilizzato presso il Dipartimento DTU Fotonik, Copenhagen, in una serie di esperimenti atti a indagare il regime di luce lenta e i ritardi ottenibili in tale regime.

Habitat loss is the greatest contributor to the decline of species globally and thus understanding habitat use and the consequences fragmentation has on biodiversity is a fundamental step towards management and recovery. I conducted a radio-telemetry study to examine the spatial ecology and the effects of roads on Eastern Hognose Snakes (Heterodon platirhinos), a species at risk, in the Long Point Region of Ontario, Canada. I tested habitat selection at multiple spatial scales and I found that within the home range, snakes avoided agricultural land and selected open sand barrens, particularly for nesting. At the local scale, snakes avoided mature overstory trees and used younger patches of forest. Used locations had more woody debris, logs and low-vegetative coverage than locations selected at random. Eastern Hognose Snakes also showed avoidance of paved road crossings in their seasonal movements, but readily crossed unpaved roads. Management efforts for this species at risk should be placed on the conservation of sand barrens and on the construction of road underpasses to prevent genetic isolation of populations.

Pour préparer les futures missions sur satellites en radioastronomie, le CNES est responsable d'un projet de ballon stratosphérique appelé PRONAOS-SMH pour lequel notre laboratoire doit construire le récepteur à 380 GHz. Ce projet est décrit dans l'introduction. Dans le premier chapitre, j'expose les bases de la supraconductivité, de l'effet Josephson et du fonctionnement du mélangeur SIS. Le chapitre II développe la technologie utilisée pour la fabrication des jonctions SIS: les principes de l'évaporation, de la pulvérisation, de la gravure et de la photolithographie y sont expliqués. Le troisième chapitre est plus particulièrement consacré à la description et à l'optimisation du procédé de fabrication des jonctions en Nb/AI-A1Ox/Nb. Des jonctions fiables de petite dimension (1 micron carré) et de forte densité de courant sont obtenues. Les études nécessaires pour parvenir à ce résultat sont détaillées. L'intégration de ces jonctions dans des récepteurs millimétriques et submillimétriques est décrite dans le chapitre IV. Les premiers résultats obtenus dans le récepteur à 380 GHz sont prometteurs : une température de bruit de 310 K DSB pour le récepteur dans son ensemble a été mesurée à 374 GHz.

NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document. This thesis describes both theoretical and experimental investigations into the dynamics and noise processes of Josephson junctions, with the intent of evaluating their potential as mixers in heterodyne instruments for submillimeter-wave (i.e., the frequency range from 300 GHz to 3THz) detection. Superconducting tunnel junctions utilizing the nonlinearity due to photon-assisted tunneling of quasiparticles (SIS mixers) have become the state-of-the-art technology for sensitive heterodyne detection up to frequencies of about 700 [...]. Recent progress in the fabrication of high [...], superconductors has led to Josephson-effect devices with [...] products of up to ten millivolts, which might be suitable for mixing at frequencies of many terahertz. The key question for weighing the prospects for high-frequency Josephson mixers is that of the sensitivity which can be attained. Previous experimental work on Josephson mixing suggests the existence of an "excess" noise, which degrades the sensitivity. Theoretical modeling of mixer performance, based on the resistivelyshunted junction (RSJ) model for the dynamics of the device, also indicates the presence of larger noise than expected. The origin of this noise was not clearly understood, however, nor was its exact magnitude or expected scaling with frequency or junction characteristics known. In addition, previous experiments utilized crude devices of the point-contact type, which were unstable and thus undesirable for real applications. In the first part of this thesis research, extensive numerical simulations were performed with the RSJ model, including calculations of mixer noise and conversion efficiency. These calculations have revealed that the source of excess noise is the AC Josephson oscillations of the device, which can be completely incoherent, with a linewidth comparable to their frequency. Thus they appear as a broadband noise source. While this noise is intrinsic and unavoidable, an optimized mixer is still shown to be capable of interesting sensitivity levels, and the excess noise is expected to become relatively less important as the operating frequency is increased. Secondly, a process has been developed for the fabrication of stable, well-characterized, and reproducible Josephson devices based on resistively-shunted Nb and NbN tunnel junctions. The devices utilize submicron-area, high current-density tunnel junctions and a AuGe shunt resistor to yield completely non-hysteretic I-V curves, normal-state resistances of about [...] products of about half a millivolt. These devices should be nearly optimal for mixing at [...]. Heterodyne measurements using these junctions have been performed in a waveguide mixer mount. Receiver temperatures as low as 190 K (DSB), with -6 dB conversion efficiency, have been obtained at 100 [...], but these results are still a factor of about four higher than those predicted by the RSJ simulations. Accurate measurements of the available noise power of the junctions at the intermediate frequency of 1.5 [...] were made, and confirmed that the receivers were limited by elevated junction output noise. The deviations of the noise from theoretical predictions are shown to be caused by the nonlinear interaction of the junction with the embedding circuit. While this work points out some of the complexity introduced by the strong nonlinearity of Josephson devices, it is still expected that Josephson-effect mixers may be useful for heterodyne detection at very high frequencies.

碩士
逢甲大學
光電研究所
100
In this research, we used optical heterodyne interferometry and RF phase-sensitive demodulation technique to measuring the linear electro-optic effect. The heterodyne interferometer is based on single acousto-optic modulator (AOM) with laser in double–pass scheme. Therefore, the components in the setup were much less than the literatures of which configurations were sophisticated, and the heterodyne frequency was operated at twice driven frequency of AOM. Notably, the arrangement was beneficial for eliminating the common-mode noise. In the first part of this thesis, the interferometer was used to measure the half-wave voltage (Vπ) of an electro-optic modulator (EOM) with two methods. First, applying voltage to EOM to obtain the demodulated amplitude (DA) and phase retardation (PR) from RF lock-in amplifier (RF LIA). By fitting data of DA and PR, the value of Vπ were calculated to be 170.42±0.78 V and 168.7±0.948 V, respectively. Second, a sinusoidal voltage was applied to modulate EOM, and the corresponding PR was measured from the RF LIA and recorded by an oscilloscope. The value of Vπ was calculated to be 173.38±0.802. In this part, we demonstrated that the value of Vπ could obtain by applying lower modulation voltage to EOM. By using this method, the influence of “waveplate effect” from the crystal of EOM could be eliminated to improve the accuracy of measurement. In the second part of this thesis, the interferometer was applied to measure the electro-optic coefficient r33 by a modified reflection technique. A sinusoidal voltage was applied to modulate the lithium niobate (LiNbO3) crystal, and the modulated PR could be measured by RF LIA. The value of r33 was calculated by using a theoretical analysis, and it turned out to be 31.7±0.2 pm/V in 780 nm. This value was close to the literatures. Since the doping concentration is unknown, we are not able to compare with the nominal value of the crystal we used.

博士
國立中央大學
光電科學研究所
98
In this article, balanced detection two-frequency heterodyne paired polarized polarimeter(BDTHP) is used to measure magnetochiral effect of Bi12SiO20 (BSO) crystal and ambient air. The Faraday rotation angle and Verdet constant of BSO crystal are 1.8×10-5(rad) and 5.27×10-5(rad/mT mm) respectively; the Faraday rotation angle and Verdet constant of ambient air are demonstrated as 5.2×10-6(rad) and 1.3×10-6(rad/mT m) respectively. In the experiment, measuring the magnetochiral effect of ambient air, the sensitivity of BDTHP is up to 1.74×10-7(rad) . If we applied a Fabry-Perot cavity with finesse F=150 and transmission coefficient K=0.1 in the balanced detection two-frequency heterodyne paired polarized polarimeter, the sensitivity of Faraday rotation angle detection will be up to 1.9×10-10(rad) . Moreover, the equal-amplitude balanced detection two-frequency heterodyne paired polarized polarimeter(EBDTHP) is proposed for measuring the mutarotation of D-glucose. The EBDTHP has the ability to degrade the error from the non-equal amplitudes of P and S waves of Zeeman He-Ne Laser. The total, forward and reversed mutarotation rate constant are k=7.67×10-5 sec-1, k1=2.76×10-5 sec-1, and k2=4.91×10-5 sec-1 respectively. The sensitivity of optical the rotation angle measurement in EBTHP was achieved with the value of 8.3×10-5 (deg/cm). The specific rotation angles of α-D-glucose 105(deg(g/L)-1 dm-1) and β-D-glucose 12(deg(g/L)-1 dm-1) are also measured by EBTHP. In summary, BTHP and EBTHP not only are capable of measuring the small optical rotation angle but also have the potential to be a research platform for biology and chemistry applications.

碩士
國立清華大學
生醫工程與環境科學系
101
Recently, many measurement methods have been used to study the structure change of protein after heating, such as differential scanning method, circularly polarized dichroism spectroscopy, X-ray diffraction crystallography method, etc. However, it is difficult for these methods to monitor the denaturation process of collagen solution in real time. In this study, a self-assembled optical heterodyne polarimeter that was capable of amplifying the optical rotation signal to 40-fold, and a precision thermoelectric cooler (TEC) were used to study the thermal denaturation phenomenon of collagen solution after heating. Our results indicated that when collagen solution was heated from 25oC to 55°C, the thermal denaturation was at 40.2±0.2°C. When the collagen solution was cooled from 55°C to 25oC, about 66% of its structure was refolded back to triple helix again. However, both the concentration of the aqueous protein solution and the rate of heating with TEC system have some effects on the processes of denaturation, but they are not the main factors. When collagen solution was mixed with Trifluoroethanol(TFE), we observed that the initial optical rotation value and the denaturation temperature were both decreased. This suggests that TFE will destroy the structure of collagen. Moreover, the destruction was saturated after the concentration of TFE exceeds 20% (v/v). At last, we added glycerol in the mixed solution of TFE and collagen. We observed that the denaturation temperature was increased when more glycerol was added. At high concentration of TFE, the protective effect is more significant than in low concentration. Not only these results can be applied to the processing of many proteins, but also are consistent with other studies using different methods.

碩士
國立清華大學
生醫工程與環境科學系
101
In the past few years, many measurement methods have been used to study the structural change of protein after heating, such as differential scanning method,circularly polarized dichroism spectroscopy, X-ray diffraction crystallography method,etc. However, these methods are not easy to monitor the denaturation process of BSA aqueous solution in real time. In this study, a homemade optical heterodyne polarimeter that was capable of amplifying the optical rotation signal for 20-fold was built up by authors, and with the use of precision thermoelectric cooler (TEC), a three-part experiments was designed to study the phenomenon of thermal denaturation of BSA aqueous solution after heating. Our results indicated that when BSA aqueous solution is heated to about 67.8°C, the thermal denaturation was observed and the structure of BSA was reversible at this time by cooling down because of protein’s renaturation role. When the temperature was between 70-75°C, its structure was gradually changed from a reversible way to a partially reversible status, and finally the structure became almost irreversible at about more than 75°C. However, although both the concentration of the aqueous protein solution and the rate of heating with TEC system have some effects on the temperature of denaturation, they are not the main factors. When BSA solution was mixed with anionic surfactants – the sodium dodecyl sulfate (SDS), to create different concentration of solution, a certain extent of stable effect on the protein structure was significantly observed when heated by our TEC system. The mixed solution avoided the structure of protein unfolding at denaturation temperature of 67.76  0.34°C, and when its concentration molar ratio [SDS] / [BSA] was about 10, the protective effect reached its maximum, making the denaturation temperature delay about 15°C. These results can not only be applied to the processing of many proteins, but also were consistent with other studies using different methods.

碩士
國立陽明大學
生醫光電工程研究所
94
To characterize multiple order wave plate (MWP) of a linear birefringent material is important because MWP is critical to the oblique incident of laser beam that MWP can become a tilted wave plate (TWP) for spectral tuning or filtering device in polarization optics. In order to avoid the oscillation of MWP on phase retardation detection, an anti-reflection coated MWP is required that the multiple-reflection of MWP can be reduced significantly. In this study, we propose a novel phase-sensitive optical heterodyne ellipsometer to verify that the oscillation on phase retardation measurement is caused by multiple reflections experimentally. Therefore, we propose a synchronized subtraction algorithm on two tilted-angle phase retardation measurements scanning in x-z plane and y-z plane respectively that not only is able to eliminate the oscillation on phase retardation measurement but also to reduce the spatial shifting effect of both eigen-polarizations of MWP at the same time. This results in a high sensitivity on linear birefringence parameters (LBP) measurement which includes the refractive indices, no, ne, thickness and phase retardation , also the order m and the orientation of optical axis of MWP simultaneously. In the meantime, a theoretical derivation of phase retardation of TWP including the spatial-shifting effect of two eigen-polarizations is accomplished too. To our knowledge, this optical setup is for the first time able to measure LBP simultaneously and precisely by using an uncoated MWP. The experimental results well agree with the theoretical calculation that promises a larger dynamical range of tilted angle of the incident laser beam than conventional method on TWP for spectral tuning and filtering purposes.

碩士
國立交通大學
光電系統研究所
101
For the first time, we report the usage of heterodyne-interferometric phase measurements to study electro-optical effects of a rubbed-polyimide-aligned twisted nematic (TN) liquid crystal (LC) cell caused by ionic impurities within the cell. Our experimental results have confirmed that, in some cases, the dominant ionic species in LC mixtures used for TFT-TNs came from impurities of low-ionization-rate(LIR) in agreement with recent publications. However, for the first time, we have observed, in some cases, ions from both high-ionization-rate (HIR) and LIR impurities have existed in the rubbed PI alignment layers of TN cells. Also, for the first time, we have carried out numerical calculations using our ion generation and transport equations to analyze and fit the measured phase data. We have obtained ion concentration and ion mobility for LIR ions within LC mixture and both HIR and LIR ions in the PI alignment layers at different temperatures. From the measured temperature-dependent phase data, we have derived the activation energies of ion-dissociation and ionic mobility of the LC mixture, and activation energies of ion-dissociation of PI alignment layers, within the TN cell. At present, we don’t know the origin and chemical compositions and structures of these HIR and LIR impurities in the LC mixture and rubbed PI films. However, we believe that, by using the experimental and analytical methods reported in this thesis to do further studies on samples of various chemical compositions and process parameters, we can find out the origins as well as chemical and structural properties of these HIR and LIR impurities and their associated ions. We hope that further researches will lead us to realize high-quality and impurity-ion-free rubbed PI alignment layers for TFT-LCDs with high-display qualities without image sticking. Although both phase and intensity measurements can be used to study electro-optical phenomena caused by field-driven net mobile ions accumulated at the interfaces between the LC mixture and the PI alignment layers of the TN cell, we believe that the phase measurement reported in this thesis is more stable and effective. The analytical and experimental methods reported in this thesis can also be applied to study the ionic effects of LC cells made from non-contact LC alignments.