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Osley, E. J. "Tunable field enhancement in plasmonic nanostructures." Thesis, University College London (University of London), 2013. http://discovery.ucl.ac.uk/1400567/.
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Metallic nanostructures that contain bound geometries will support localised surface plasmon (LSP) resonances if they are illuminated with light of appropriate frequency. These LSP resonances result in a concentration of the electric field of the incident light into a volume which is smaller than the photon wavelength. Certain geometries that support LSP resonances are sensitive to the polarisation of incident light, and the enhanced electromagnetic field can therefore be tuned in situ by adjusting this polarisation. We have investigated polarisation tunable LSP field enhancement by observing, in the linear regime, the interaction of an asymmetric cruciform aperture structure with a chemical bond and, in the non-linear regime, the second harmonic generation (SHG) produced by three metallic nanostructures. Numerical simulations implementing rigorous coupled-wave analysis (RCWA) were used to find asymmetric cruciform aperture dimensions that produced LSP resonances when illuminated with light of a wavelength between 2 μm and 8 μm. Arrays of these apertures were fabricated in a 35 nm thick gold film on a transparent calcium fluoride (CaF_{2}) substrate. The fabrication methods used to create the apertures were either focused ion beam (FIB) milling, or electron beam lithography (EBL) with argon ion milling, of the gold film. Fourier transform infrared spectroscopy (FTIR) was used to measure the transmission and reflection spectra of these plasmonic nanostructures. The apertures were coated with poly(methyl methacrylate) (PMMA), which has a local absorption maximum at 5.784 μm created by the stretching of its carbonyl bonds. The transmission and reflection spectra of the PMMA-coated apertures were measured using FTIR. The interaction of the LSP and molecular resonances was shown to form an asymmetric Fano resonance at the carbonyl bond wavelength. We found that this Fano resonance can be tuned in situ by rotating the polarisation of incident light. A classical mechanical oscillator model was developed to interpret the reflection and transmission spectrum in terms of the interference of the LSP and molecular resonances. A quantum mechanical model was also developed and used to predict the absorption spectrum of the system. This quantum mechanical model provides information on the physical interactions within the system, and predicts a near-field mediated interaction between the plasmon and molecular resonances. Nonlinear optical measurements were made using an SHG microscope, which allowed the location of near-field SHG hotspots to be determined. Three geometries were measured using this technique using fundamental wavelengths of 800 nm or 1 μm. The first geometry, a chiral star structure, was found to display dichroic SHG that was dependent on the handedness of the incident circularly-polarised fundamental light. The second, a `windmill' structure, was used to investigate the dependence of near-field SHG on the linear polarisation of fundamental light; the ablation of these metallic windmill structures by the fundamental demonstrates that laser ablation of patterned surfaces is dependent on the LSP resonance of the constituent structures. Finally, the spatial dependence of SHG produced by a cruciform aperture structure in a gold film illuminated by linearly polarised light was observed. SHG intensity was found to be greatest along the axis of the cruciform which was perpendicular to the incident E field polarisation.
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Séguin, Guy. "Enhancement of efficiency and accuracy of near-field measurements." Thesis, McGill University, 1997. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=35612.
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This thesis examines the possibility of increasing the speed of Near-Field measurement of an Antenna, by reducing the number of measurement points and by determining the degree of truncation permissible while maintaining a prescribed degree of precision of the reconstructed far-field.The mathematical formulation leading to the near-field to far-field transform is presented in a novel and simpler form to use. Relations are established between the selected area and sampling rate of Near-Field measurement and the accuracy of the Far-Field of an Antenna. The spectral domain of the field is analysed in each case and parametric curves are derived. Correction of the spectral domain can significantly improve the accuracy of the Far-Field while using the same amount of Near-Field data.
A new concept, described as the Signature Function, is presented, analysed and tested. This new concept offers the possibility of conducting a highly reduced set of measurements while producing accurate results for antennas whose "Signature Function" is previously determined or can be estimated.
The simulated Near-Field of a radiating array is analysed in depth. A formulation and a procedure to correct the spectral domain of the field are established.
The technique developed is applied to experimental and simulated Near-Field data of large radiating Antennas leading to new information about the accuracy and speed of measurement achievable.
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Grönqvist, Helena. "Vision Enhancement Systems : The Importance of Field of View." Thesis, Linköping University, Department of Computer and Information Science, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-1370.
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The purpose of the project, which led to this thesis, was to investigate the possible effects different horizontal Fields of View (FoV) have on driving performance when driving at night with a Vision Enhancement System (VES). The FoV chosen to be examined were 12 degree and 24 degree FoV, both displayed on a screen with the horizontal size of 12 degree FoV. This meant that the different conditions of FoV also had different display ratios 1:1 and 1:2. No effort was made to separate these parameters.
A simulator study was performed at the simulator at IKP, Linköping University. Sixteen participants in a within-group design participated in the study. The participants drove two road sections; one with a 12 degree FoV and the other with a 24 degree FoV. During each section four scenarios were presented in which the participants passed one of three types of objects; a moose, a deer or a man. In each section, two of the objects stood right next to the road and two were standing seventeen meters to the right of the road. As the drivers approached the objects standing seventeen meters to the right of the road, the objects moved out of the VES when the vehicle was 200 meters in front of the object with a 12 degree FoV. The objects could be seen with the naked eye when the vehicle was 100 meters in front of the object. When the drivers approached the objects with a 24degree FoV the objects moved out of the VES display when it was possible to see them unaided.
Results show that a 24 degree FoV displayed with a 1:2 ratio gives the drivers improved anticipatory control, compared to a 12 degree FoV displayed with a 1:1 ratio. The participants with a broader FoV were able to make informed decisions whereas with a narrow FoV some participants started to reaccelerate when they could not see an object. Results also show that any difference in recognition distance that may exist between a 12 degree and a 24 degree camera angle displayed in a 12 degree FoV display do not seem to have any adverse effect on the quality of driving.
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Seguin, Guy. "Enhancement of efficiency and accuracy of near-field measurements." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0018/NQ44576.pdf.
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Dücker, Eibe Behrend. "Enhancement Strategies in NMR Spectroscopy." Doctoral thesis, Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2018. http://hdl.handle.net/11858/00-1735-0000-002E-E3E4-9.
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Fischer, Janina [Verfasser]. "Near-field mediated enhancement effects on plasmonic nanostructures / Janina Fischer." Mainz : Universitätsbibliothek Mainz, 2012. http://d-nb.info/1019193654/34.
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Huang, Danian. "Enhancement of automatic interpretation techniques for recognising potential field sources." Thesis, University of Leeds, 1996. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.719809.
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Hearn, Christian Windsor. "Electrically-Small Antenna Performance Enhancement for Near-Field Detuning Environments." Diss., Virginia Tech, 2012. http://hdl.handle.net/10919/49554.
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Bandwidth enhancement of low-profile omnidirectional, electrically-small antennas has evolved from the design and construction of AM transmitter towers eighty years ago to current market demand for battery-powered personal communication devices. Electrically-small antenna theory developed with well-known approximations for characterizing radiation properties of antenna structures that are fractions of the radiansphere. Current state-of-the-art wideband small antennas near kaH1 have achieved multiple-octave impedance bandwidths when utilizing volume-efficient designs. Significant advances in both the power and miniaturization of microelectronics have created a second possible approach to enhance bandwidth. Frequency agility, via switch tuning of reconfigurable structures, offers the possibility of the direct integration of high-speed electronics to the antenna structure. The potential result would provide a means to translate a narrow instantaneous bandwidth across a wider operating bandwidth.
One objective of the research was to create a direct comparison of the passive- multi-resonant and active-reconfigurable approaches to enhance bandwidth. Typically, volume-efficient, wideband antennas are unattractive candidates for low-profile applications and conversely, active electronics integrated directly antenna elements continue to introduce problematic loss mechanisms at the proof-of-concept level.
The dissertation presents an analysis method for wide bandwidth self-resonant antennas that exist in the 0.5dkad1.0 range. The combined approach utilizes the quality factor extracted directly from impedance response data in addition to near-and-far field modal analyses. Examples from several classes of antennas investigated are presented with practical boundary conditions. The resultant radiation properties of these antenna-finite ground plane systems are characterized by an appreciable percentage of radiated power outside the lowest-order mode.
Volume-efficient structures and non-omnidirectional radiation characteristics are generally not viable for portable devices. Several examples of passive structures, representing different antenna classes are investigated. A PIN diode, switch-tuned low-profile antenna prototype was also developed for the comparison which demonstrated excessive loss in the physical prototype.
Lastly, a passive, low-profile multi-resonant antenna element with monopole radiation is introduced. The structure is an extension of the planar inverted-F antenna with the addition of a capacitance-coupled parasitic to enhance reliable operation in unknown environments.
Ph. D.
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Bur, Christian. "Selectivity Enhancement of Gas Sensitive Field Effect Transistors by Dynamic Operation." Doctoral thesis, Linköpings universitet, Tillämpad sensorvetenskap, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-114670.
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Gas sensitive field effect transistors based on silicon carbide, SiC-FETs, have been applied to various applications mainly in the area of exhaust and combustion monitoring. So far, these sensors have normally been operated at constant temperatures and adaptations to specific applications have been done by material and transducer platform optimization. In this thesis, the methodology of dynamic operation for selectivity enhancement is systematically developed for SiC-FETs. Temperature cycling, which is well known for metal oxide gas sensors, is transferred to SiC-FETs. Additionally, gate bias modulation is introduced increasing the performance further. The multi-dimensional sensor data are evaluated by use of pattern recognition mainly based on multivariate statistics. Different strategies for feature selection, crossvalidation, and classification methods are studied. After developing the methodology of dynamic operation, i.e., applying the virtual multi-sensor approach on SiC-FETs, the concept is validated by two different case studies under laboratory conditions: Discrimination of typical exhaust gases and quantification of nitrogen oxides in a varying background is presented. Additionally, discrimination and quantification of volatile organic compounds in the low parts-perbillion range for indoor air quality applications is demonstrated. The selectivity of SiC-FETs is enhanced further by combining temperature and gate bias cycled operation. Stability is increased by extended training.Gaskänsliga fält-effekt-transistorer baserade på halvledarmaterialet kiselkarbid (SiC-FET) har redan framgångsrikt använts för olika tillämpningar främst inom området för avgas- och förbränningsövervakning. Normalt har dessa sensorer använts vid konstant temperatur och anpassning till specifika tillämpningar har gjorts av material och sensor optimering. I denna avhandling har metoden för dynamisk modulering systematiskt utvecklats för att ökaselektiviteten av SiC-FETs. Temperatur-cykling är en välkänd metod för metalloxidsensorer och har nu tillämpats på SiC-FETs för första gången. Likaså har den pålagda gatepotentialen varierats. Mönsterigenkänningsmetoder baserade på multivariat statistik används för att utvärdera multi-dimensionella sensordata. Olika strategier för urval, korsvalidering och klassificering av okända uppgifter studeras. Efter att metodiken för dynamiska mätmetoder har beskrivits i detalj, verifieras strategin av virtuella-multisensorer genom två tester under laboratorieförhållanden. Detta visas av exemplet med separering av typiska avgaser och bestämning av koncentrationen av kväveoxider i varierande gasblandningar. Vidare har ett test genomförts där flyktiga organiska föreningar identifieras och kvantifieras för att bestämma kvaliteten på inomhusluft. Dessutom kan man öka selektiviteten av sensorerna genom att kombinera modulering av temperatur och gate-potential.
Gassensitive Feldeffekt-Transistoren basierend auf Siliziumkarbid (SiC-FET) werden überwiegend für die Abgasmessung eingesetzt. Üblicherweise werden diese Sensoren bei konstanter Temperatur betrieben. Durch die Auswahl geeigneter Materialien sowie durch die Modifikation der Sensoren können diese für verschiedene Anwendungen optimiert werden. In der vorliegenden Dissertation wird die Methodik einer dynamischen Betriebsweise zur Selektivitätssteigerung systematisch weiterentwickelt. Temperaturmodulation ist ein bewährtes Verfahren für Halbleitergassensoren, das hier auf SiC-FETs übertragen wird. In ähnlicher Weise wird auch das Gate-Potential zyklisch variiert. Mustererkennungsverfahren basierend auf multivariater Statistik werden eingesetzt, um die mehrdimensionalen Messdaten auszuwerten. Verschiedene Verfahren zur Merkmalsauswahl, Kreuzvalidierung und Klassifikation unbekannter Daten werden untersucht. Nachdem die Methodik ausführlich dargelegt wurde, wird der Ansatz des virtuellen Multisensors anhand zweier Anwendungen unter Laborbedingungen verifiziert. Dies wird am Beispiel der Konzentrationsbestimmung von Stickoxiden in variierenden Gasgemischen gezeigt. Zudem werden flüchtige organische Verbindungen im niedrigen ppb-Bereich zur Bestimmung der Innenraumluftqualität erkannt und quantifiziert. Die Selektivität kann durch die Kombination von Temperatur- und Potentialmodulation weiter gesteigert und Drifteinflüsse durch erweitertes Training kompensiert werden.
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Bocan, Jiri. "Sensitivity enhancement and field-dependent relaxation in singlet nuclear magnetic resonance." Thesis, University of Southampton, 2013. https://eprints.soton.ac.uk/354550/.
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Nitrous oxide (N2O), also known as "laughing" gas, is a well known compound used in medicine as a mild anaesthetic, or in engineering as a powerful oxidizer providing highoutput of engines. Recently, its 15N doubly-labelled isotopologue attracted attention in singlet NMR due to its long singlet relaxation time ranging between 7 minutes, when dissolved in blood, up to 26 minutes in degassed dimethyl sulfoxide (DMSO). Singlet NMR deals with nuclear singlet states, which are exchange antisymmetric quantum states of coupled pairs of spin-1/2 nuclei with zero total nuclear spin quantum number. These states are nonmagnetic and immune to exchange-symmetric relaxation processes such as intramolecular direct dipolar relaxation. Their lifetimes may be up to an order of magnitude longer than conventional relaxation times T1 and T2. Besides various fields of NMR, singlet states find potential application also in MRI. The direct medical application of 15N2O as a MRI tracer is, however, complicated by a poor detection sensitivity resulting from the low 15N magnetogyric ratio, low solubility in liquids at room temperature and atmospheric pressure, and limitations of 15N signal enhancement by means of physical methods for dissolved 15N2O. This thesis addresses two topics related to singlet NMR of 15N2O { sensitivity enhancement and magnetic-field dependent relaxation. The NMR signal decay in liquid phase is often dominated by static magnetic �eld inhomogeneity, described by the time constantT�2 , which is much faster than the transverse relaxation, characterized by T2. Repeated refocusing by a multiple spin-echo (MSE) train maintains the 15N signal for extended times of several T2. Acquisition of the signal during the whole MSE sequence followed by a proper processing either by matched weighting or singular value decomposition, may lead to the signal-to noise ratio (SNR) enhancement by up to an order of magnitude under favourable circumstances. The SNR enhancement is a function of T2, T� 2, and the spectral resolution. The procedure of the SNR enhancement in combination with methods of singlet NMR was used to investigate in detail low-field 15N2O singlet relaxation. The 15N2O relaxation measurements were extended to field strengths up to the spectrometer high field. The observed relaxation dependencies were described by a general theory, relaxation as a time-dependent exchange of populations of the �eld-dependent energy eigenstates. In particular, spin-rotation relaxation in low field was discussed.
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PUEO, ORTEGA BASILIO JAVIER. "Analysis and enhancement of multiactuator panels for wave field synthesis reproduction." Doctoral thesis, Universitat Politècnica de València, 2008. http://hdl.handle.net/10251/3347.
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Esta tesis aborda el desarrollo y mejora de los altavoces de panel multiexcitados (MAPs) con particular importancia en su aplicación para la reproducción de síntesis de campo (WFS). Los altavoces MAPs pueden usarse como alternativa a las agrupaciones de altavoces dinámicos para WFS con ventajas adicionales. Sin embargo, puesto que los altavoces MAPs son paneles finitos que se excitan en varios puntos de su superficie, existen cuestiones estructurales y geométricas que deben ser tratadas para garantizar que todos los excitadores actúan uniformemente para crear una agrupación de altavoces válida para WFS. Este objetivo se acomete a través de un método para el análisis de la radiación del campo sonoro en el dominio espacio-temporal que ha sido propuesto y validado en esta tesis. De la presente investigación se desprenden diversas conclusiones. El método propuesto analiza las imperfecciones del campo sonoro por el submuestreo espacial en una representación gráfica que muestra la distribución de energía radiada en el espacio. Mediante un estudio comparativo entre altavoces MAPs de diferentes tamaños y agrupaciones de altavoces dinámicos, la principal conclusión que se desprende, con implicaciones prácticas, es que el campo creado por paneles de grandes dimensiones presenta menos imperfecciones que el de paneles pequeños equivalentes. El efecto del contorno del panel en la calidad del campo creado también se ha considerado al comparar varias condiciones de contorno con diversos materiales elásticos. La conclusión principal es la conveniencia de usar condiciones elásticas que pueden crear una tecnología viable de sujeción de paneles y que presentan una radiación acústica adecuada. Los bordes también afectan a la respuesta de los excitadores cercanos, que debe ser convenientemente ecualizada para obtener una respuesta similar a la de los excitadores centrales.Pueo Ortega, BJ. (2008). Analysis and enhancement of multiactuator panels for wave field synthesis reproduction [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/3347
Palancia
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Boddepalli, Srinivasarao. "Enhancement of field emission from multistage structure of carbon nanotube arrays." FIU Digital Commons, 2007. http://digitalcommons.fiu.edu/etd/1708.
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The field emission measurements for the multistage structured nanotubes (i.e., thin-multiwall and single wall carbon nanotubes grown on multiwall carbon nanotubes) were carried out and a low turn-on field of ~0.45 V/ μm, high emission current of 450 μA at a field of IV/μm and a large field enhancement factor of ~26200 were obtained. The thin multiwall carbon nanotubes (thin-MWNTs) and single wall carbon nanotubes (SWNTs) were grown on the regular arrays of vertically aligned multi wall carbon nanotubes (MWNTs) on porous silicon substrate by Chemical Vapor Deposition (CVD) method. The thin-MWNTs and SWNTs grown on MWNTs in this way have a multistage structure which gives higher enhancement of the electric field and hence the electron field emission.
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Ahmad, Syed Waqas. "Combined effect of electric field and surface modification on pool boiling of R-123." Thesis, Brunel University, 2012. http://bura.brunel.ac.uk/handle/2438/6600.
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The effect of surface modification and high intensity electric field (uniform and non – uniform) acting separately or in combination on pool boiling of R-123 is presented in this thesis. The effect of surface modification was investigated on saturated pool boiling of R-123 for five horizontal copper surfaces modified by different treatments, namely: an emery polished surface, a fine sandblasted surface, a rough sandblasted surface, an electron beam (EB) enhanced surface and a sintered surface. Each 40 mm diameter heating surface formed the upper face of an oxygen-free copper block, electrically heated by embedded cartridge heaters. The experiments were performed from the convective heat transfer regime to the critical heat flux, with both increasing and decreasing heat flux, at 1.01 bar, and additionally at 2 bar and 4 bar for the emery polished surface. Significant enhancement of heat transfer with increasing surface modification was demonstrated, particularly for the EB enhanced and sintered surfaces. The emery polished and sandblasted surface results are compared with nucleate boiling correlations and other published data. The effect of uniform and non-uniform electric fields on saturated pool boiling of R-123 at 1.01 bar pressure was also examined. This method of heat transfer enhancement is known as electrohydrodynamic abbreviated as EHD-enhancement. A high voltage potential was applied at the electrode located above the heating surface, which was earthed. The voltage was varied from 0 to 30 kV. The uniform electric field was provided through a 40 mm diameter circular electrode of stainless steel 304 wire mesh having an aperture of 5.1 mm, while the non-uniform electric field was obtained by using a 40 mm diameter circular rod electrode with rods 5 and 8 mm apart. The effect of uniform electric field was investigated using all five modified surfaces, i.e. emery polished, fine sandblasted, rough sandblasted, EB enhanced and sintered surfaces, while non – uniform electric field was tested using the emery polished, fine sandblasted, EB enhanced and sintered surfaces. The effect of pressure on EHD enhancement was also examined using emery polished surface at saturation pressure of 2 and 4 bars while the electric field was fix at 20 kV corresponding to 2 MV/m. Further, the bubble dynamics is presented for the emery polished surface obtained using a high-speed high – resolution camera.
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Chevaux, Nicolas. "Contributing to enhancement of power field effect transistors for radio frequency applications." Thesis, University of Sheffield, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.632414.
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Fernandez, Garcia Roberto. "Simulation and characterization of optical nanoantennas for field enhancement and waveguide coupling." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/18846.
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Optical antennas are nanostructures designed to efficiently convert free-propagating optical radiation to localized energy and vice versa. They are based on localized surface plasmon resonances (LSPRs) that generally exist in metal nanoparticles (NPs). The excitation of LSPRs can lead to large near field enhancements and to an increase of the near field effective area up to several times the physical cross section of the nanoparticle. These properties can be used to increase the interaction of any object located in their vicinity with free space radiation. In this thesis, we investigate experimentally and numerically the interactions of nanoantennas with different systems like organic emitters, graphene and dielectric waveguides. we have numerically reviewed important experimental factors that generally control the optical antennas properties. Substrates, metal sticking layers, geometries or dimensions can significantly influence the maximum near field enhancement and the resonance wavelength that optical antennas can provide for spectroscopies like Surface enhanced Raman Scattering, (SERS) and Photoluminiscence, (PL). In particular, we experimentally analyse the influence of the incorporation of a metallic reflecting layer. This provide a straightforward way to increase the photoluminescence enhancement of nanoemitters induced by optical nanotantennas. Regarding SERS applications, we probe with surface-enhanced Raman scattering the plasmonic properties of an isolated Au double disk nanostructure interfaced with suspended graphene. By rotating the polarization of the excitation, we switch between the dots acting as single plasmonic particles and a coupling regime, realizing a plasmonic cavity. we observe a Raman intensity enhancement of the order of 1000 resulting from the near- field enhancement at the antenna cavity.
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Byambadorj, Tsenguun. "Optimization of the bowtie gap geometry for a maximum electric field enhancement." Thesis, Marquette University, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10242847.
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Optimization of the geometry of a metallic bowtie gap at radio frequency is presented in this thesis. Since the design and fabrication of a plasmonic device (nanogap) at nanoscale is challenging, the results of this study can be used to estimate the best design parameters for nanogap structure. The geometry of the bowtie gap including gap size, tip width, metal thickness, and tip angle are investigated at macroscale to find the maximum electric field enhancement across the gap. This thesis focuses on the simulation portion of a work that consists of experimental and simulation platforms. The simulation platform is created by NEC modeling system using antenna segments. The results indicate that 90? bowtie with 0.06 ? gap size has the most |Et|2 enhancement. Different amounts of enhancement at different frequency ranges are explained by mode volume. The product of the mode volume and |Et|2 enhancement is constant for different gap structures and different frequencies.
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Franz, Dominik. "High harmonic generation in crystals assisted by local field enhancement in nanostructures." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS128/document.
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Le but de cette thèse est d’étudier le processus de la génération d’harmoniques d’ordre élevé (HHG, de l’anglais high-order harmonic generation) dans des solides et la possibilité d’augmenter l’efficacité de la génération en exploitant l’exaltation locale du champ incident dans des nanostructures. La HHG dans les gaz est connue depuis plusieurs décennies et a été étudiée en détails, par contre la HHG dans les solides a été démontrée pour la première fois en 2011. Différents processus comme les oscillations interbandes et intrabandes y jouent un rôle fondamental. Le processus exact est toujours en cours d’investigation et est discuté dans la communauté. Dans ce manuscrit, nous étudions la génération d’harmoniques dans différents cristaux, comme ZnO, CaCO₃ et CdWO₄. Nous confirmons que la HHG dépend de la longueur d’onde génératrice et de l’orientation cristalline. Outre les cristaux 3D nous étudions la HHG dans des matériaux 2D comme le graphène. Grâce à sa grande mobilité électronique et sa structure de bande spécifique la HHG dans graphène est plus efficaces que dans des cristaux 3D.Typiquement des intensités de 10¹² TW/cm² ou plus sont nécessaires pour susciter la HHG. Ces intensités élevées sont généralement atteintes par des méthodes comme l’amplification par dérive de fréquence qui génère des impulsions femtosecondes à des énergies µJ ou mJ. Grâce aux progrès récents des techniques de nanofabrication, il est possible d’exalter un champ électrique laser de plusieurs ordres de grandeurs dans des nanostructures. Alors que la HHG dans les gaz assistée par la plasmonique a été démontrée comme n’étant pas réalisable, des travaux récents démontrent l’amplification de la HHG dans des solides. Dans ce travail, nous étudions l’amplification de la HHG dans différentes configurations. D’abord, nous analysons différents types de nanostructures, à savoir des bow ties, des nano-trous, des réseaux et des résonateurs. Nous comparons ces structures suivant plusieurs critères tels que le volume d’exaltation et l’exaltation crête. Différentes longueurs d’onde et cristaux sont utilisés. Une large amplification de plusieurs ordres de grandeur est démontrée pour la troisième harmonique. En plus, nous discutons l’endommagement des nanostructures causé par l’irradiation laser. Des nanostructures semiconductrices confinant la lumière par guidage sub-longueur d’onde ont plusieurs avantages par rapport aux nanostructures métalliques. Des nanocones semiconducteurs, par exemple, présentent un grand volume d’amplification, supérieur de plusieurs ordres de grandeur à ce qui a été démontré récemment, et évitent la fusion observée dans des nanostructures métalliques. Nous présentons plusieurs itérations de l’expérience avec des nanocones de ZnO en améliorant le système de détection et la géométrie des nanocones entre chaque étape. Nous utilisons différents lasers et différentes géométries de nanocones. Nous avons observé les harmoniques d’un laser à 3.1 µm dans des nanocones de ZnO jusqu’à l’ordre 15. L’amplification de plusieurs ordres de grandeur d’harmoniques perturbatives et non perturbatives, générées à partir des impulsions d’un oscillateur nanojoule à une cadence MHz et une longueur d’onde de 2.1 µm, est démontrée pour la première fois jusqu’à H9. Le facteur d’amplification dépend de l’éclairement du faisceau pompe. Nous étudions également la forte amplification de la luminescence et proposons des méthodes pour séparer sa contribution de la contribution cohérente. En outre, nous démontrons plusieurs applications de la HHG dans les solides. Premièrement, nous proposons une nouvelle méthode pour déduire la distribution spatiale du champ électrique dans des nanostructures en analysant les dommages induits par laser. Deuxièmement, nous utilisons l’émission du nanocone, qui est cohérente spatialement, pour imager des objets avec une résolution à l’échelle nanométrique. Enfin, nous générons des harmoniques portant un moment orbital angulaire contrôléThe aim of this dissertation is to study the process of high-order harmonic generation (HHG) in solids and the possibility to amplify solid HHG by exploiting local field enhancements in nanostructures. While HHG in gases has been known for several decades and has been extensively studied, HHG in solids was first reported in 2011. Different processes such as interband and intraband oscillations were identified to play an important role in solid HHG. However, the process is still under investigation and debated in the community. Here, we study the generation of high harmonics in different crystals, such as ZnO, CaCO₃ and CdWO₄. We confirm that HHG depends on the driving wavelengths and on crystalline orientation. Beside 3D bulk crystals, we investigate HHG in 2D materials such as graphene. Due to its high electron mobility and its special band structure HHG in graphene is more efficient than in bulk crystals. Typically, intensities of 10¹² TW/cm² or more are needed to trigger HHG. The high intensity is reached by employing schemes like chirped pulse amplification which generates femtosecond pulses with µJ- or mJ-energies. Thanks to recent advances in nanofabrication techniques, nanostructures can enhance a laser electric field by several orders of magnitude. While plasmonically enhanced HHG in gases was shown not to be feasible, recent works reported on the amplification of HHG in solids. In this work, we explore the amplification of crystal HHG under various configurations. We first study different types of plasmonic nanostructures, namely bow ties, nanoholes, gratings and resonators. We compare them with respect to different parameters such as enhancement volume and peak enhancement. Different driving wavelengths and crystals are used. Strong amplification by several orders of magnitude is demonstrated for the third harmonic. Furthermore, we discuss radiation-induced damage of plasmonic nanostructures. Semiconductor nanostructures which confine light by subwavelength waveguiding have several advantages with respect to metallic nanostructures. Semiconductor nanocones for example exhibit a large amplification volume, several orders of magnitudes larger than previously reported and avoid melting observed in metallic nanostructures. We carry out several iterations of experiments with ZnO nanocones where the detection system and the nanocone geometry are improved in each cycle. We use different driving lasers and different optimized nanocone geometries. HHG in ZnO nanocones up to 15th order from a 3.1 µm driving laser is demonstrated. Amplification by several orders of magnitude of both perturbative and non-perturbative harmonics from nanojoule-oscillator pulses at MHz repetition rate and 2.1 µm wavelength is demonstrated, for the first time up to H9. The amplification factor depends on the pump intensity. We also explore the strong amplification of luminescence and propose ways to disentangle its contribution from the coherent one. Furthermore, we explore several applications of crystal HHG. First, we propose a new way to deduce the electric field spatial distribution in nanostructures by analyzing the radiation-induced damage. Secondly, we use the spatially coherent emission from the nanocone to image nanoscale objects with nanometer scale resolution. In addition, we generate solid harmonics that carry an orbital angular momentum
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Narendar, Harish. "A Simulation Study of Enhancement mode Indium Arsenide Nanowire Field Effect Transistor." University of Cincinnati / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1259080514.
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Kwan, Man-chi. "Mobility enhancement for organic thin-film transistors using nitridation method." Click to view the E-thesis via HKUTO, 2006. http://sunzi.lib.hku.hk/hkuto/record/B37181580.
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Kwan, Man-chi, and 關敏志. "Mobility enhancement for organic thin-film transistors using nitridation method." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2006. http://hub.hku.hk/bib/B37181580.
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Abdelaal, Mohamed Riad Mohamed. "Electric Field Driven Enhancement of Heat and Mass Transfer to a Liquid Drop." University of Cincinnati / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1321968954.
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Subramanian, Rajkumar. "Heat Transfer to a Droplet Translating in an Electric Field." University of Cincinnati / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1108851150.
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Bur, Christian [Verfasser]. "Selectivity Enhancement of Gas Sensitive Field Effect Transistors by Dynamic Operation / Christian Bur." Aachen : Shaker, 2015. http://d-nb.info/1075437172/34.
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Sanyal, Poulomi. "Depth of field enhancement of a particle analyzer microscope using wave-front coding." Thesis, McGill University, 2005. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=83931.
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In this thesis we present an analytical solution to the problem of improving the depth of field (DOF) of a certain large magnification imaging system with a high numerical aperture (NA), illuminated with an incoherent source of light. As there is a definite trade-off between the focal depth and resolution achievable with such a system, our challenge was to find a system that would achieve both these objectives and at the same time be cost-effective and easy to implement.Our choice of technique therefore was a novel optical wave front manipulation mechanism involving subsequent image restoration via digital post processing. This technique is known as wave front coding. The coding is achieved with the help an optical element known as a phase plate and then the coded image is electronically restored with the help of a digital post-processing filter.
The three steps involved in achieving our desired goal were, modeling the imaging system to be studied and studying its characteristics before DOF enhancement, designing the phase plate and finally, choosing and designing the appropriate decoding filter. After an appropriate phase plate was modeled, it was incorporated into the pre-existing optics and subsequently optimized. The intermediate image produced by the resulting system was then studied for defocus performance. Finally, the intermediate image was restored using a digital filter and studied once again for DOF characteristics. Other factors, like optical aberrations that might limit system performance were also taken into consideration.
In the end a simpler and cost-effective method of fabricating the suggested phase plate for single-wavelength operation was suggested. The results of our simulations were promising and sufficiently high resolution imaging was achievable within the entire enhanced DOF region of +/-200 mum from the point of best focus. The DOF without coding was around +/-50 mum, but with coding the spot size remained fairly constant over the entire 400 mum deep region of interest. Thus a 4 times increase in the overall system DOF was achieved due to wave front coding.
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Malik, Kazim A. "An intelligent portfolio management approach to gas storage field deliverability maintenance and enhancement." Morgantown, W. Va. : [West Virginia University Libraries], 2006. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=4833.
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Thesis (M.S.)--West Virginia University, 2006.Title from document title page. Document formatted into pages; contains vii, 105 p. : ill. (some col.) ; map (part col.). Includes abstract. Includes bibliographical references (p. 58-59).
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Rethwisch, Michael D., Manuel M. Luna, D. Michael Ramos, Jessica J. Wellman, and Mark Reay. "Field Comparison of Various Plant Growth Enhancement Products on DPL 449BR Cotton, 2005." College of Agriculture, University of Arizona (Tucson, AZ), 2006. http://hdl.handle.net/10150/198197.
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Three plant growth enhancement chemistries (AuxiGro®, ChaperoneTM, HappyGroTM) were evaluated on DPL 449BR cotton during the summer of 2005, Application were made during mid-July to late planted cotton to evaluate and compare effects of these products on cotton growing under severe heat and growth stress to determine if such chemistries could overcome this stress. Two foliar fertilizers were included with two formulations of AuxiGro® to determine if differences associated with these treatments existed. Usage of HappyGroTM = PhotoGroTM resulted in the most fruiting structures/plant while treatments that included ChaperoneTM resulted in reduced numbers of structures when compared with the untreated check on August 24. Highest yields among products tested were noted for the formulations of AuxiGro® 518 which were slightly higher than the untreated check. Quality was improved in comparative formulations of AuxiGro® by inclusion of CalMax® + First Choice® Foliar Pride when compared with First Choice® Bollster.
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Lin, Jeng-Weei James. "Enhancement of user-experiences in immersive virtual environments that employ wide-field displays /." Thesis, Connect to this title online; UW restricted, 2004. http://hdl.handle.net/1773/10680.
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Ouyang, Qiqing Christine. "Physical model enhancement and exploration of bandgap engineering in novel sub-100nm pMOSFETs /." Digital version:, 2000. http://wwwlib.umi.com/cr/utexas/fullcit?p9992880.
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Romero, Orellana Fredy Rolando. "Enhancement of plant performance and biochemical constituents in field and hairy root production of Echinacea." [Ames, Iowa : Iowa State University], 2006.
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Guo, Luke (Luke W. ). "Enhancement of antimonide-based p-channel quantum-well field effect transistors using process-induced sprain." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/82389.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2013.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 55-57).
For decades, the scaling of silicon CMOS has brought impressive growth to the semiconductor industry, as well as a wealth of technological innovations. However, the continued scaling of CMOS devices to the nanometer regime is now threatened by intrinsic limitations to the use of silicon as the channel material. Hence, there is a strong interest in III-V semiconductor materials to replace silicon as the channel material as a result of their outstanding electron transport properties. While III-V materials have demonstrated impressive n-channel field-effect transistors (FETs), the same success has not yet been translated to the development of a high-performance III-V pchannel FET. This is because while many III-V's have high electron mobilities, they generally have very poor hole mobilities. The development of a high-performance III-V p-channel FET is critical to the realization of a future-generation III-V CMOS architecture. Among the III-Vs, the antimonides have the highest hole mobilities. This makes them attractive for developing a 111-V p-channel FET. This thesis examines the use of process-induced uniaxial strain combined with biaxial strain introduced during growth of the heterostructure as an approach to enhance antimonide-based FETs. Using a compressively stressed silicon nitride layer to induce uniaxial strain in the device, stressed devices with an InGaSb channel were fabricated and compared with unstressed devices processed in parallel. Enhancements of >50% in the intrinsic transconductance were observed as well as reductions of >30% in the source-drain resistance. This work illustrates the effectiveness of uniaxial strain in improving the performance of antimonide FETs.
by Luke Guo.
S.M.
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Matsui, Motohide. "Enhancement of field-trapping capabilities and mechanical properties of Nd-Ba-Cu-O bulk superconductors." 京都大学 (Kyoto University), 2003. http://hdl.handle.net/2433/148896.
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Yi, Congwen. "Reliability study of enhancement-mode AIGaN/GaN HEMT fabricated with fluorine plasma treatment technology /." View abstract or full-text, 2008. http://library.ust.hk/cgi/db/thesis.pl?ECED%202008%20YI.
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Martin, John Matthew. "A comprehensive experimental study of a few Ce based compounds exhibiting an enhancement in #gamma# at low temperatures." Thesis, University of Warwick, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.263572.
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Camporesi, Silvia. "From bench to bedside, to track and field : the context of enhancement and its ethical relevance." Thesis, King's College London (University of London), 2013. https://kclpure.kcl.ac.uk/portal/en/theses/from-bench-to-bedside-to-track-and-field(474eb5e1-e0ee-4f5b-88c4-49e3887e63d0).html.
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This thesis addresses enhancement technologies and their ethical permissibility through a contextual, bottom up approach based on case studies. The first chapter presents various definitions of 'enhancement', arguments for and against, and discusses the therapy/enhancement distinction. The second chapter discusses applying genetic technologies from bendh to bedside, analysing: the objections to reprogenetics grounded in 'eugenics'; and, how pre-implantation genetic diagnosis (PGD) and other embryonic genetic screening techniques, as well as genetic tests sold online directly-to-the-consumer (DTC) to measure children's athletic potential raise a conflict between parental reproductive freedom and children's rights to an open future and capacity for self-determination. Chapter 3 turns to how genetic technologies are translated directly from the molecular medicine laboratory to "track & field," analysing: the scientific and regulatory context of gene enhancement, and on which basis it is classified as doping; how the International Olympic Committee and the International Association for Athletics Federation incorrectly consider hyperandrogenism an unfair advantage; and, the World Anti Doping Agency Code and its current revisions. Chapter 4 discusses enhancements in a democratic society, and addresses the neglected issue of justifying enhancement research (ER). I propose: a model in which cognitive enhancements, currently prescribed under a 'disease' model, could instead be prescribed under an 'enhancement' model; and, a possible justification for ER that translates the ethical criteria justifying clinical research to the enhancement context. I then consider possible changes society would need to implement to accommodate ER. The last chapter attempts to advance the discussion of enhancement by shifting the debate from ethics to policymaking, arguing for a deliberative democracy approach. Throughout, I adopt a casuistic approach to ethics, deploying tools from consequentialist, principled and virtue ethics. I try to break the stalemate between enhancement's proponents and opponents, and discuss the ethical permissibility of technologies in ways that could inform policymaking.
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Hua, Xiaoben, and Yuxia Yang. "A Fusion Model For Enhancement of Range Images." Thesis, Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-2203.
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In this thesis, we would like to present a new way to enhance the “depth map” image which is called as the fusion of depth images. The goal of our thesis is to try to enhance the “depth images” through a fusion of different classification methods. For that, we will use three similar but different methodologies, the Graph-Cut, Super-Pixel and Principal Component Analysis algorithms to solve the enhancement and output of our result. After that, we will compare the effect of the enhancement of our result with the original depth images. This result indicates the effectiveness of our methodology.Room 401, No.56, Lane 21, Yin Gao Road, Shanghai, China
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Thomas, Sebastian [Verfasser], and Peter [Akademischer Betreuer] Hommelhoff. "Interaction-free measurements with electrons and optical field enhancement at nanotips / Sebastian Thomas. Betreuer: Peter Hommelhoff." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2016. http://d-nb.info/1098130715/34.
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Eichel, Rüdiger-Albert. "New concepts in two-dimensional pulse electron paramagnetic resonance spectroscopy : resolution enhancement by magnetic field modulation /." Zürich : [s.n.], 2001. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=14394.
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Collins, Clare Melissa. "Ordered nanomaterials for electron field emission." Thesis, University of Cambridge, 2017. https://www.repository.cam.ac.uk/handle/1810/270357.
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In the quest for reliable, repeatable and stable field electron emission that has commercial potential, whilst many attempts have been made, none yet has been truly distinguishable as being successful. Whilst I do not claim within this thesis to have uncovered the secret to success, fundamental issues have been addressed that concern the future directions towards achieving its full potential. An exhaustive comparison is made across the diverse range of materials that have, over the past 40-50 years, been postulated and indeed tested as field emitters. This has not previously been attempted. The materials are assessed according to the important metrics of turn on voltage, Eon, and maximum current density, Jmax, where low Eon and high Jmax are seen as desirable. The nano-carbons, carbon nanotubes (CNTs), in particular, perform well in both these metrics. No dependency was seen between the material work function and its performance as an emitter, which might have been suggested by the Fowler Nordheim equations. To address the issues underlying the definition of the local enhancement factor, β, a number of variations of surface geometry using CNTs were fabricated. The field emission of these emitters was measured using two different approaches. The first is a Scanning Electrode Field Emission Microscope, SAFEM, which maps the emission at individual locations across the surface of the emitter, and the parallel plate that is more commonly encountered in field emission measurements. Finally, an observed hysteretic behaviour in CNT field emission was explored. The field emitters were subjected to a number of tests. These included; in-situ residual gas analysis of the gas species in the emitter environment, a stability study in which the emitters were exposed to a continuing voltage loop for 50 cycles, differing applied voltage times to analyse the effects on the emitted current, and varying maximums of applied field in a search for hysteresis onset information. These studies revealed the candidate in causing the hysteresis is likely to be water vapour that adsorbs on the CNT surface. A six step model if the emission process was made that details how and when the hysteresis is caused.
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Wang, Ruonan. "Enhancement/depletion-mode HEMT technology for III-nitride mixed-signal and RF applications /." View abstract or full-text, 2008. http://library.ust.hk/cgi/db/thesis.pl?ECED%202008%20WANG.
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Aizawa, Hirohito, Kazuhiko Kuroki, and Yukio Tanaka. "Strong magnetic field enhancement of spin triplet pairing arising from coexisting 2k_F spin and 2k_F charge fluctuations." American Physical Society, 2008. http://hdl.handle.net/2237/11284.
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Gullapalli, Sai Krishna. "Wave-Digital FPGA Architectures of 4-D Depth Enhancement Filters for Real-Time Light Field Image Processing." University of Akron / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=akron1574443263497981.
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Wang, Yuji. "Ultra-Sensitive AlGaN/GaN HFET Biosensors: Performance Enhancement, Clinical and Food Safety Applications." The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1409017537.
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"Field enhancement using noble metal structures." 2012. http://library.cuhk.edu.hk/record=b5549483.
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共振是自然界一個基本物理過程。特別是，在納米尺度上的光頻電磁諧振產生顯著的場增強，提供了一種手段來影響和控制光與物質的相互作用。例如，巨大的場增強使表面增強拉曼散射具有探測單個分子的靈敏度。此外，場增強可以使發光二極體具有更高亮度高，但輸入功率更低。雖然場增強在一些關鍵技術領域大有前途，有許多挑戰仍有待解決。由於場增強是如此強烈地依賴系統的幾可形狀即使稍作修改可以導致大的結果變化，因此理解幾何結構如何影響場增強和可重複的製造這些車前壽是最重要的。因此本論文致力於設計，製造和貴金屬如銀或金的一維結構的表面上生成的場增強特性。首先對s-偏振下一維金屬光栅產生的場增強使用嚴格購合波分析(RCWA) 進行了設計和優化。優化後，在514nm 波長最強的增強因數是9.7 。製作了一維光栅並進行角度相關的反射率測量，實驗結果與理論計算相符。
對一種新型利用表面等離子激元的呻吟加強電場的單縫桔構進行了研究。首先利用用衰減全反射搞合在50 納米厚的金屬薄膜上產生sp恥，隨後利用spps 驅動這一狹縫。結果發現縫內場增強至少3 倍於狹縫附近的等離子激元背景。其增強機理用數值和分析的方法進行理論研究。
提出了兩種新型的製造高深寬比納米縫隙的簡便方法。一個是在飯有金膜的薄玻璃上製造裂紋，獲得了寬度小於5nm 具有一定平整度的抗縫，通過掃描電子顯微鏡圖像和共焦雙光子發射(CTPE) 光譜和時間域有限差分模擬的對比得到了確認。另一種是對鍍有金膜的柔性基底進行疲勞彎折，獲得了大量狹縫。觀察到CTPE 和二次諧波產生從這些縫中產生。
採用電子束光刻製作了納米縫並使用CTPE 進行了表徵。提出一種新方法對激發波長和發射波長的增強因數進行了分解。發現脈衝錯射能調整EBL 樣品的共振波長到錯射波長。提出了一種機制解釋這一現像。進一步實驗表明這是一種製造任意共振波長場增強熱點的有用方法。
Resonance may be one of the most fundamental rules of nature. Electromagnetic resonance at nanometer scale could produce a giant field enhancement at optical frequency, providing a way to measure and control the process of atoms and molecules at single molecule scale. For example, the giant field enhancement would provide single molecule sensitivity for Raman scattering, which provides unique tools in measuring the quantity in extremely low concentration. In addition, light-emitting diodes could have high brightness but low input power that would be revolutionary in the optoelectronic industry. Although light enhancement is promising in several key technology areas, there are several challenges remain to be tackled. In particular, since the field enhancement is so strongly geometry dependent that slight modification of the geometry can lead to large variations in the outcome, a thorough understanding in how the geometry of the structure affects the field enhancement and creating proper methods to fabricate these structures reproducibly is of most importance. This thesis is devoted to design, fabrication and characterization of field enhancement generated on the surface of noble metals such as silver or gold with 1D structure.
The s-polarized field enhancement arISIng from one-dimensional metal gratings IS designed and optimized by using Rigorous Coupling Wave Analysis (RCWA). After optimization, the strongest enhancement factor is found to be 9.7 for 514nm wavelength light. The theoretical results are confirmed by angle-dependent reflectivity measurements and the experimental results are found to support the theory.
A novel single slit structure employing sUlface plasmon polaritons (SPPs) for enhancing the electric field is studied. SPPs are first generated on a 50 nm thick metal film using attenuated total reflection coupling, and they are subsequently coupled to the cavity mode induced by the single slit. As a result, the field enhancement is found at least 3 times the surface plasmon background adjacent to the slit, as predicted by using RCWA. The mechanism for enhancement is theoretically studied both numerically and analytically.
Two novel convenient methods for fabricating nanoslits with high aspect ratio are proposed. One is creating nanoslits by cracking the thin glass substrates with metal film. Sub-Snm wide slits with fair uniformity are created, as confirmed by Scanning Electron Microscopy images and comparing the Confocal Two Photon Emission (CTPE) spectroscopy with finite difference in time domain simulations. The other is creating slits by fatiguing the metal film on a flexible substrate. Enhanced CTPE and second harmonic generation are observed arising from these less than 20nm wide slits.
Nanoslits fabricated using Electron Beam Lithography (EBL) are characterized using CTPE. The overall emission enhancement of excitation and collection wavelengths is separated by a proposed method. It is surprisingly found that the pulsing laser can tune the resonant wavelength of the EBL samples to the laser wavelength. A mechanism is proposed for this phenomenon. It is shown this can be developed into a tool to fabricate field enhancement hot spots.
Detailed summary in vernacular field only.
Detailed summary in vernacular field only.
Detailed summary in vernacular field only.
Detailed summary in vernacular field only.
Detailed summary in vernacular field only.
Liu, Benliang = 用貴金屬結構增強場強 / 劉本良.
Thesis (Ph.D.)--Chinese University of Hong Kong, 2012.
Includes bibliographical references (leaves 133-137).
Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web.
Abstract also in Chinese.
Liu, Benliang = Yong gui jin shu jie gou zeng qiang chang qiang / Liu Benliang.
Acknowledgement --- p.i
Abstract --- p.ii
摘要 --- p.iv
List of figures --- p.1
Chapter 1 --- Overview --- p.1
Chapter 1.1 --- Introduction --- p.1
Chapter 1.2 --- Applications of field enhancement --- p.1
Chapter 1.2.1 --- Surface enhanced Raman scattering --- p.1
Chapter 1.2.2 --- Enhanced luminescence --- p.4
Chapter 1.3 --- Fundamentals of field enhancement --- p.5
Chapter 1.3.1 --- The Maxwell's equations --- p.6
Chapter 1.3.2 --- Boundary conditions --- p.8
Chapter 1.3.3 --- Phase matching condition --- p.10
Chapter 1.3.4 --- Dipole --- p.11
Chapter 1.3.5 --- Purcell factor --- p.12
Chapter 1.3.6 --- Mode and mode interaction --- p.13
Chapter 1.3.7 --- Surface plasmon resonance --- p.14
Chapter 1.3.8 --- Fabry-Perot cavity resonance --- p.16
Chapter 1.4 --- Overview of the nanofabrication methods of metal structures for field enhancement --- p.17
Chapter 1.4.1 --- Photolithography --- p.18
Chapter 1.4.2 --- Electron Beam Lithography --- p.20
Chapter 1.4.3 --- Focused ion beam --- p.21
Chapter 1.4.4 --- Summary --- p.21
Chapter 2 --- Methods of simulation --- p.26
Chapter 2.1 --- Rigorous coupled wave analysis framework --- p.26
Chapter 2.1.1 --- FormulaofRCWA --- p.26
Chapter 2.1.2 --- Expression ofMaxwell's equations in Fourier space --- p.27
Chapter 2.1.3 --- Numerical shooting method --- p.29
Chapter 2.1.4 --- Reflection efficiency, transmission efficiency and absorption --- p.32
Chapter 2.1.5 --- Convergence test of the RCWA simulation --- p.33
Chapter 2.2 --- Finite difference in time domain --- p.34
Chapter 2.2.1 --- Formulations of FDTD --- p.34
Chapter 2.2.2 --- Dispersion of dielectric constant --- p.35
Chapter 2.2.3 --- Boundary conditions and excitation sources --- p.37
Chapter 3 --- Investigation of s-polarized resonance on 1D grating --- p.40
Chapter 3.1 --- Introduction --- p.40
Chapter 3.2 --- Theoretical results of the s-polarized resonance in the 1D grating --- p.41
Chapter 3.3 --- Discussion of the theoretical results --- p.47
Chapter 3.3.1 --- Origination of the s-polarized resonance modes --- p.47
Chapter 3.3.2 --- Position discrepancy between absorption peaks and reflection dips --- p.48
Chapter 3.3.3 --- Absorption beyond the cutoff wavelength of reflectance --- p.48
Chapter 3.3.4 --- Absorption wavelength dependency on the periodicity --- p.50
Chapter 3.4 --- Effects of parameters on absorption and electric field --- p.50
Chapter 3.5 --- Optimization the s-polarized resonance for field enhancement --- p.54
Chapter 3.6 --- Angle dependency of the optimized resonant mode --- p.55
Chapter 3.7 --- Grating preparation and characterization --- p.57
Chapter 3.8 --- Experimental results and discussion --- p.59
Chapter 3.9 --- Summary --- p.73
Reference --- p.74
Chapter 4 --- Fabricating and characterizing nanoslit-shaped resonant cavity --- p.75
Chapter 4.1 --- Introduction --- p.75
Chapter 4.2 --- Confocal two photon emission measurement --- p.78
Chapter 4.2.1 --- Background --- p.78
Chapter 4.2.2 --- Polarization dependence of the confocal system --- p.79
Chapter 4.3 --- Decomposition of excitation and collection TPL enhancement --- p.81
Chapter 4.4 --- Fabrication and characterization of slits by cracking glass substrate --- p.83
Chapter 4.4.1 --- Fabrication of nanoslits by cracking glass --- p.83
Chapter 4.4.2 --- Characterization of the nanoslits by cracking glass substrates --- p.86
Chapter 4.4.2.1 --- Two-photon emission from rough slits 86
Chapter 4.4.2.2 --- Location dependence of the two-photon emission --- p.87
Chapter 4.4.2.3 --- Relation between reflection and two-photon emission --- p.88
Chapter 4.4.2.4 --- Wavelength dependence ofTPLfrom the slits by cracking glass --- p.89
Chapter 4.4.3 --- Discussion --- p.97
Chapter 4.4.4 --- Summary --- p.98
Chapter 4.5 --- Fabrication and characterization of nanoslits by fatigue --- p.98
Chapter 4.5.1 --- Fabrication ofnanoslits by fatigue --- p.98
Chapter 4.5.2 --- Characterization ofnanoslits by fatigue --- p.100
Chapter 4.5.3 --- Discussion --- p.105
Chapter 4.6 --- Two photon emission from nanoslits by EBL --- p.106
Chapter 4.6.1 --- Sample preparation --- p.107
Chapter 4.6.2 --- Characterization of the slits made by Electron Beam Lithography --- p.109
Chapter 4.6.2.1 --- Reflected light extinction and two photon emission --- p.109
Chapter 4.6.2.2 --- Wavelength dependence of TPL enhancement --- p.120
Chapter 4.6.2.3 --- Laser modification of resonant wavelength of the cavity --- p.124
Chapter 4.6.2.4 --- Discussion --- p.126
Chapter 4.6.3 --- Summary --- p.132
Chapter 5 --- Conclusion --- p.138
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Boybay, Muhammed Said. "Sensitivity Enhancement of Near Field Probes Using Negative Materials." Thesis, 2009. http://hdl.handle.net/10012/4597.
Full textAbstract:
In the last decade, design and application of negative materials have been one of the most interesting subjects in the electromagnetic research. The extraordinary properties of double negative (DNG) and single negative (SNG) materials have been studied extensively over this period. In this thesis, one of the unusual properties of negative materials, the evanescent amplification, is used to improve the sensitivity of the near field probes.
The effect of placing DNG and SNG layers between the near field probes and the targets are investigated theoretically. A sensitivity definition is introduced for evanescent probes and it is shown using quantitative measures that the sensitivity can be increased using DNG and SNG materials for a target in vacuum and for a buried target. The electromagnetic loss of the negative materials and the mismatch between the material properties of the host medium and DNG and SNG materials are studied. Using an unmatched DNG layer or SNG layer enhances the sensitivity within an evanescent spectrum range while a lossless and matched DNG layer improves the sensitivity of entire evanescent spectrum.
The idea of using negative materials is implemented over conventional near field probes by numerical experiments. Sensitivities of open-ended waveguides and open-ended coaxial lines for a specific application are studied in the presence of negative materials. In the case of precursor pitting detection on airplane bodies, the sensitivity of an open-ended waveguide probe is increased by 35 times for a λ/10 sized cubic crack. It is also shown that the negative material increases the quality of the image generated by the probe. The sensitivity improvement is also verified for an open-ended coaxial line. A 11 times improvement is achieved for a similar detection practice, with a λ/20 sized crack. The effect of coaxial line size and the dielectric material on the sensitivity enhancement are studied.
The improvement is studied theoretically and numerically for an electrically small dipole. Theoretical studies show that when a small dipole is placed within a spherical shell made of DNG materials, the antenna parameters of the dipole becomes more sensitive to the position of a target placed outside the negative material shell. The field distribution generated by a small dipole in a multilayered spherical medium is studied for this purpose. Numerical analysis of a small dipole placed next to a planar DNG layer is presented. The DNG layer increases the sensitivity of the dipole due to a λ/30 sized metallic target by 5.5 times.
To provide experimental verification, the sensitivity of an electrically small loop is studied. SNG materials with a negative permeability around 1.25 GHz are designed using modified split ring resonators (MSRR). By using the effective parameters of the designed structure, a sensitivity improvement of 10 times is achieved numerically. The improvement is verified using fabricated MSRR structures. The sensitivity of the small loop is enhanced by 9 times for a λ/12.2 sized metallic target. The sensitivity improvements are achieved within the frequency band where the MSRR structures behave as a μ-negative SNG material.
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Chung, Meng-Yu, and 鐘孟瑜. "Acoustic Field Enhancement Using a Stereo Headphone." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/47277474427068453102.
Full textAbstract:
碩士國立中正大學
電機工程所
98
This thesis proposes a technique of acoustic field enhancement under a listening condition using a stereo headphone. This technique is to explore stereo widening and stereo deepening of a sound field. In this work, the critical bands of psychoacoustics are adopted to decrease inter-correlation of stereo channels for stereo widening. Thereby, directions of sound sources are enhanced. Additionally, an immersive sound field is built for good sound image under fair transparency of sound quality. In stereo deepening, the field depth is improved according to phenomena of reverberation and shadowing in an acoustic environment. To reach this goal, the full search of two delay impulses in a time domain is conducted at difference critical bands. The experimental results exhibit that the proposed acoustic field enhancement technique not only effectively decreases inter-correlation of stereo channels, but also present excellent sound-field spaciousness and surrounding sense.
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YANG, YING-SHENG, and 楊穎昇. "Context-Aware Sound Field Enhancement for Headphones." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/46604396523608511808.
Full textAbstract:
碩士國立中正大學
電機工程研究所
101
In this thesis, we proposed a technique of context-aware acoustic field enhancement under a listening condition using a stereo headphone. The architecture consists of three parts which are blind audio separation, acoustic field enhancement and virtual bass enhancement. In the blind audio separation system, we use commercial audio tracks’ mixture mathematical characteristics of left and right channels to carry out time-frequency binary mask, and then separate dominate sound (vocal and dialogues) and subordinate sound (incidental music and surrounding sound). In the acoustic field enhancement system, based on different audio property, we provide appropriate enhancers as follows: In the incidental music part, reduce left and right channels’ correlation to achieve externalization, decrease listening fatigue and expand the acoustic sound field as more as possible. In the speech part, we utilize an equalizer to enhance the consonants’ frequency bands, to achieve speech intelligibility. In the vocal part, the full search of two delay impulses at a time domain is conducted at difference critical bands, in order to make the vocal with the accompaniment more matchable. Finally, considering the physical characteristic of headphones, we adopt the missing fundamental phenomenon to enhance low frequency bands. The experimental results reveal that our method can make the dominate sound of movie audio more transparency compare with conventional acoustic field enhancement method. Summing of the above three systems, our method present excellent sound-field spaciousness, clear dialog, deep bass and immersive surrounding sense. Keywords：Blind Audio Separation, De-correlation, Externalization, Virtual Bass Enhancement, Speech Intelligibility Enhancement
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Kuo, Po-Chen, and 郭柏辰. "Far-Field Speech Enhancement Technique for Home Environments." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/83073067040149959736.
Full textAbstract:
碩士國立中正大學
電機工程研究所
104
With the advance of science and technology, replacing characters with voices as the input information for the system is reachable. The voice-input electronic products have been widely applied in recent years. In our life, whether we use telephones, Skype, Siri or sound surveillance system, the main objective of them is to recognize human’s voice clearly. But these communication devices are often disturbed by the environmental noises, and further cause users unable to understand speaker’s content. Thus, to make speaker’s voice more clearly, speech enhancement technique plays an important role in audio signal processing. In this thesis, we combine two methods of speech enhancement, that is, spectral subtraction and MMSE-STSA. First, we will do spectral subtraction, and then consider noise components to decide whether according to the variances of every noise frequency band to give them different gain functions by MMSE-STSA algorithm. In addition, according to the noises of this thesis, it will enhance its speech components by using different frame sizes. By means of our experiments, we give the audio signal large frame size when speech components are low; otherwise, we give small frame sizes. Finally, we use objective and subjective quality measure to show the experimental results. In the air and white Gaussian noise condition, most conditions will improve compared with the conventional method. Also, the method we proposed will get a better capability of noise reduction than conventional method by subjective quality measure. The objective of this study is applied for home-care environment. By preliminary results of this study, it could improve subsequent recognition rate of speakers’. It can be more reliable for home-care system by above-mentioned method.
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Harrison, Richard K. 1982. "Mechanisms and applications of near-field and far-field enhancement using plasmonic nanoparticles." Thesis, 2012. http://hdl.handle.net/2152/19462.
Full textAbstract:
The resonant interaction of light with metal nanoparticles can result in extraordinary optical effects in both the near and far fields. Plasmonics, the study of this interaction, has the potential to enhance performance in a wide range of applications, including sensing, photovoltaics, photocatalysis, biomedical imaging, diagnostics, and treatment. However, the mechanisms of plasmonic enhancement often remain poorly understood, limiting the design and effectiveness of plasmonics for advanced applications. This dissertation focuses on evaluating the mechanisms of plasmonic enhancement and distinguishing between near and far field effects using simulations and experimental results.
Thorough characterization of metal nanoparticle colloids shows that electromagnetic simulations can be used to accurately predict the optical response of nanoparticles only if the true shapes and size distributions are taken into account. By coupling these optical interaction calculations with heat transfer models, experimental limits for the maximum optical power before nanoparticle melting can be found. These limits are important for plasmonic multiphoton luminescence imaging applications. Subsequently, we demonstrate ultrafast laser plasmonic nanoablation of silicon substrates using gold nanorods to identify the near-field enhancement and mechanism of plasmon-assisted ablation. The experimentally observed shape of the ablation region and reduction of the ablation threshold are compared with simulations to show the importance of the enhanced electromagnetic fields in near-field nanoablation with plasmonic nanoparticles.
The targeted use of plasmonic nanoparticles requires narrow size distribution colloids, because wide size distributions result in a blurring and weakening of the optical response. A new synthesis method is presented for the seeded-growth of nearly monodisperse metal nanoparticles ranging from 10 to 100 nm in diameter, both with and without dielectric shells of controlled thickness. This method is used to acquire fine control over the position and width of the plasmonic peak response. We also demonstrate self-assembled sub-monolayers of these particles with controllable concentrations, which is ideal for looking at plasmonic effects in surface and layered geometries.
Finally, we present results for the spatial distribution of absorption around plasmonic nanoparticles. We introduce field-based definitions for distinguishing near-field and far-field regions and develop a new set of equations to determine the point-by-point enhanced absorption in a medium around a plasmonic nanoparticle. This set of equations is used to study plasmon-enhanced optical absorption for thin-film photovoltaic cells. Plasmonic nanoparticle systems are identified using simulations and proof-of-concept experiments are used to demonstrate the potential of this approach.
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Smith, Robert Levi. "Terahertz Field Enhancement by Optimized Coupling and Adiabatic Tapering." Thesis, 2014. http://hdl.handle.net/1828/5671.
Full textAbstract:
Waveguides are desirable components for energy transmission throughout the electromagnetic spectrum. This thesis experimentally examines a thick slot waveguide for THz guiding and field enhancement. The waveguide is machined from planar copper sheets using the novel technique of femtosecond laser micromachining. In-plane photoconductive THz coupling to a thick slot waveguide is demonstrated using Discontinuous Galerkin Time Domain (DGTD) simulation. The results reveal positive
implications for broadband low-loss/dispersion transmission lines up to 1.5 THz.Graduate
0544
0607
0756
levismith3@hotmail.com
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(5929772), Yu-Chun Hsueh. "Field Control and Optical Force Enhancement with Aperiodic Nanostructures." Thesis, 2019.
Find full textAbstract:
Aperiodic structures offer new functionalities for control, manipulation, and sensing that can benefit applications in all frequency ranges. We present a study of the influence of the degrees of freedom from a binary aperiodic nanostructure in free space, where each pixel is either the scatterer or the background, that uses a multivariate statistical analysis to examine the covariance matrix of the output field distributions. The total variance of the output fields and the rank can be evaluated to provide quantitative measurements of control. In addition, the field statistics provide an improved understanding of the scattering properties of aperiodic structures.
It has been proposed that structuring a metal surface can substantially increase the optical pressure over that possible with a planar interface. Based upon the forces on the mirrors of a one-dimensional asymmetric Fabry-Perot cavity, we show that the sum of the pressures on both mirrors increases through asymmetry and with quality factor. Using cavity quality factor as a measure, we present the physical basis of the enhanced pressure on a nanostructured metallic surface as being due to an array of asymmetric resonant cavities.
With use of optimized, aperiodic structures, more control and higher pressure should be possible. We present a design method by which the electromagnetic pressure on a nanostructured binary material can be controlled in terms of both the enhancement and the direction. This analysis offers new avenues for optomechanics.