Este trabalho apresenta o estudo, a implementação e a caracterização de transdutores compostos por uma estrutura formada por grades de Bragg (FBG, Fiber Bragg Gratings) e grades de período longo (LPG, Long Period Gratings) em fibra óptica com cobertura metálica autoaquecida para medição da condutividade térmica e da difusividade térmica de materiais baseado no método do fio quente (HWM, Hot-Wire Method) convencional. O autoaquecimento da fibra óptica do dispositivo desenvolvido neste trabalho é provocado pela luz de espectro infravermelho injetada por um laser de bombeamento, que é espalhada por uma LPG e absorvida por um filme fino metálico depositado na superfície da fibra. Os transdutores apresentados são compactos, simples, robustos e imunes a interferências eletromagnéticas. O arranjo experimental utilizando o dispositivo híbrido LPG-FBG foi capaz de medir as condutividades térmicas do ar atmosférico e da água comum com precisões de 27% e 14%, respectivamente. Foram identificados vários fatores que afetam a precisão e a exatidão das medidas realizadas, sendo propostas diversas formas de correções de modo a melhorar o desempenho do arranjo. Foi demonstrada com sucesso a viabilidade da aplicação original do arranjo experimental utilizando o dispositivo híbrido LPG-FBG em fibra óptica autoaquecida para a medição de propriedades térmicas de fluidos (ar e água). / This work presents the study, implementation, and characterization of transducers composed of a structure formed by Fiber Bragg Gratings (FBG) and Long Period Gratings (LPG) in optical fiber with self-heating coverage for measurement of thermal conductivity and thermal diffusivity of materials based on the Hot-Wire Method (HWM). The self-heating fiber optic device developed in this work is caused by the light of infrared spectrum injected by a pumping laser, which is spread by an LPG and absorbed by a thin metallic film deposited on the surface of the fiber. The transducers are compact, simple, robust and immune to electromagnetic interference. The experimental arrangement using the optical fiber sensor based on LPG-FBG hybrid structure was able to measure the thermal conductivity of atmospheric air and water with accuracies of 27% and 14%, respectively. Several factors were identified that affect the precision and the accuracy of the measures carried out, whereby various forms of corrections are being proposed to improve overall performance. The viability of the original application of the experimental arrangement using the LPG-FBG hybrid device in self-heating optical fiber for the measurement of thermal properties of fluids (air and water) has been successfully demonstrated.

Polímeros contendo grupos azo-benzênicos têm sido estudados devido a sua capacidade para óptica não linear, formação de superfícies de relevo e de birrefringência fotoinduzida. O fator que possibilita essas aplicações é a propriedade de fotoisomerização reversível trans-cis-trans do grupo azo que produz a sua reorientação molecular. Neste trabalho foram produzidos filmes casting do poliuretano MDI-DR19 derivado de azo-benzeno. Estudou-se o crescimento e decaimento da birrefringência para diferentes valores de potência da luz de excitação da fotoisomerização. Os resultados experimentais do crescimento e decaimento foram analisados usando duas exponenciais e eles mostraram que o polímero MDI-DR19 apresenta boas características para utilização em armazenamento óptico pois cerca de 65% da birrefringência induzida no material permanece por longos intervalos de tempo. Ilustramos o processo de armazenamento de informação gravando uma imagem de birrefringência num filme de MDI-DR19. Foram também produzidas grades de relevo em filmes de MDI-DR19 utilizando franjas de interferência produzidas com luz de polarização P e S. Essas grades apresentaram alta uniformidade e características compatíveis com as mostradas na literatura. / Polymers containing azobenzenic groups have been studied due to their applications on non-linear optics, surface relief gratings (SRG) and photoinduced anisotropy for optical storage. The reversal photoisomerization trans-cis-trans property of the azo group induces a molecular reorientation. In this work, cast films of na azobenzene derivative, the polyurethane MDI-DR19, were studied. The build-up and decay of the birefringence were studied as a function of the photoisomerization exciting light power. The data of the build-up and decay of the birefringence were fitted with a bi-exponential function, which shows the stability of the MDI-DR19 for application in optical storage, since 65% of the induced birefringence remains after a long time. The optical storage is illustrated by recording a birefringence image in a film of MDI-DR19. It was also performed a SRG over films of MDI-DR19 applying an interference finger pattern with a P and S polarized light. The light induced gratings shows good uniformity and characteristics compatible with those presented in the literature.

Este trabalho apresenta o estudo, a implementação e a caracterização de transdutores compostos por uma estrutura formada por grades de Bragg (FBG, Fiber Bragg Gratings) e grades de período longo (LPG, Long Period Gratings) em fibra óptica com cobertura metálica autoaquecida para medição da condutividade térmica e da difusividade térmica de materiais baseado no método do fio quente (HWM, Hot-Wire Method) convencional. O autoaquecimento da fibra óptica do dispositivo desenvolvido neste trabalho é provocado pela luz de espectro infravermelho injetada por um laser de bombeamento, que é espalhada por uma LPG e absorvida por um filme fino metálico depositado na superfície da fibra. Os transdutores apresentados são compactos, simples, robustos e imunes a interferências eletromagnéticas. O arranjo experimental utilizando o dispositivo híbrido LPG-FBG foi capaz de medir as condutividades térmicas do ar atmosférico e da água comum com precisões de 27% e 14%, respectivamente. Foram identificados vários fatores que afetam a precisão e a exatidão das medidas realizadas, sendo propostas diversas formas de correções de modo a melhorar o desempenho do arranjo. Foi demonstrada com sucesso a viabilidade da aplicação original do arranjo experimental utilizando o dispositivo híbrido LPG-FBG em fibra óptica autoaquecida para a medição de propriedades térmicas de fluidos (ar e água). / This work presents the study, implementation, and characterization of transducers composed of a structure formed by Fiber Bragg Gratings (FBG) and Long Period Gratings (LPG) in optical fiber with self-heating coverage for measurement of thermal conductivity and thermal diffusivity of materials based on the Hot-Wire Method (HWM). The self-heating fiber optic device developed in this work is caused by the light of infrared spectrum injected by a pumping laser, which is spread by an LPG and absorbed by a thin metallic film deposited on the surface of the fiber. The transducers are compact, simple, robust and immune to electromagnetic interference. The experimental arrangement using the optical fiber sensor based on LPG-FBG hybrid structure was able to measure the thermal conductivity of atmospheric air and water with accuracies of 27% and 14%, respectively. Several factors were identified that affect the precision and the accuracy of the measures carried out, whereby various forms of corrections are being proposed to improve overall performance. The viability of the original application of the experimental arrangement using the LPG-FBG hybrid device in self-heating optical fiber for the measurement of thermal properties of fluids (air and water) has been successfully demonstrated.

Les dispositifs magnéto-optiques (MO) sont les éléments de base des isolateurs optiques, éléments essentiels pour les lasers et LIDAR. Ils sont également utilisés pour l'imagerie, le stockage ou les capteurs. Une structuration périodique du matériau magnétique est un moyen pour en améliorer les performances, et ainsi réduire la taille des composants intégrés ou améliorés la sensibilité des capteurs associés. Cependant, la mise en œuvre des matériaux magnéto-optiques habituels au sein des platefo1mes d'optique intégrée est rendue difficile par la forte température de cristallisation (- 7000C) qu'ils requièrent. En utilisant un processus sol-gel basse température, une matrice de silice peut être dopée par des nanoparticules magnétiques (C0Fe204) pour produire un matériau qui présente une excellente compatibilité avec les substrats photoniques. Dans ce travail, ce matériau composite a été utilisé pour imprégner un réseau grâce à un dépôt en une seule étape à une température inférieure à 100 °C. Il s'agit d'un réseau lD ShN4 sur verre. Des simulations numériques, basées sur les méthodes RCW A, et réalisées à 1,55 µm ont permis de déterminer les paramètres adéquats pour obtenir un réseau résonnant, simultanément pour les polarisations TE et TM, à incidence normale. Les simulations MO ont démontré que ce type de structure permet d'obtenir l'exaltation de tous les effets magnéto-optiques classiques (Kerr et Faraday). Le facteur de mérite théorique obtenu est comparable voir supérieur à ceux rapportés dans la littérature qui utilisent des matériaux MO classiques. Ces améliorations ont été confirmées par des réalisations et caractérisations expérimentales. Par exemple, une augmentation de la rotation de Faraday d'un facteur 3,5 a été obtenue par rapport à un film mince de référence. Le facteur de mérite correspondant était comparable voir supérieur à ceux présentés dans la littérature prouvant la grande efficacité de notre structure. Les résultats de ce travail sont la première démonstration d'une augmentation de tous les effets MO avec un seul dispositif / Magneto-optical (MO) devices are the basic elements of optical isolators essential for lasers an1 LIDAR, and are also employed for aircraft imaging, data storage or sensing. A periodic structuration of the core magnetic material is a way to enhance its MO behavior, and is thus useful to reduce the footprint of integrated devices or to improve the sensitivity of related sensors. However, the processing of efficient magnetic materials on photonic platforms is still challenging, because classical MO materials require an annealing temperature as high as 700°C. Using a sol-gel process, a silica matrix can be doped by magnetic nanoparticles (C0Fe204) to produce a MO material which possess a full compatibility with photonic substrates. In this work, this composite material was incorporated into an already structured template through a single step deposition at low temperature. The template was a 1-D SiJN4 grating on glass. Numerical simulations, based on RCW A methods, have been carried out to identify the suitable values of the grating period and the line-space ratio which produce a guided-mode resonance at 1.55 µm simultaneously for TE and TM polarizations, at normal incidence. MO simulations demonstrated that an enhancement of magneto-optical effects is obtained in transmission or reflection for every orientation of the applied magnetic field (Kerr or Faraday effects). The theoretical figure of merit for these structures were comparable or higher than those reported in literature which use classical MO materials. These enhancements were confirmed by experimental realizations and measurements. For instance, a Faraday rotation enhancement of 3.5 times was demonstrated compared to the reference thin-film. The c01Tesponding figure of merit was comparable or higher than those reported in literature proving the high efficiency of our structure. The results of this work are the 1st demonstration of an enhancement of every MO effect with a single device

Fibre-optic sensors have been the focus of a lot of research, but their associated high cost has stifled their transferral from the laboratory to real world applications. This thesis addresses the issue of multiplexing, a technology that would lower the cost per unit sensor of a sensor system dramatically. An overview of the current state of research of, and the principles behind, multiplexed sensor networks is given. A new scheme of multiplexing, designated W*DM, is developed and implemented for a fibre Bragg grating (FBG) optical fibre sensor network. Using harmonic analysis, multiplexing is performed in the domain dual to that of the wavelength domain of a sensor. This scheme for multiplexing is compatible with the most commonly used existing schemes of WDM and TDM and thus offers an expansion over, and a resultant cost decrease from, the sensor systems currently in use. This research covered a theoretical development of the scheme, a proof of principle, simulated and experimental analysis of the performance of the multiplexed system, investigation into sensor design requirements and related issues, fabrication of the sensors according to the requirements of the scheme and the successful multiplexing of eight devices (thus offering an eightfold increase over current network capacities) using this scheme. Extensions of this scheme to other fibre sensors such as Long Period Gratings (LPGs) and blazed gratings were also investigated. Two LPGs having a moir?? structure were successfully multiplexed and it was shown that a blazed Fabry Perot grating could be used as a tuneable dual strain/refractive index sensor. In performing these tests, it was discovered that moir?? LPGs exhibited a unique thermal switching behaviour, hereto unseen. Finally the application of fibre sensors to the civil engineering field was investigated. The skill of embedding optical fibre in concrete was painstakingly developed and the thermal properties of concrete were investigated using these sensors. Field tests for the structural health monitoring of a road bridge made from a novel concrete material were performed. The phenomenon of shrinkage, creep and cracking in concrete was investigated showing the potential for optical fibre sensors to be used as a viable research tool for the civil engineer.

Die Arbeit stellt neu entwickelte Röntgenbeugungsmethoden vor, mit deren Hilfe der Verzerrungszustand des Kristallgitters von Halbleiter-Wafern und -Bauteilen im Detail charakterisiert werden kann. Hierzu werden die aussergewöhnlichen Eigenschaften der an modernen Synchrotrons wie der ESRF (Grenoble) verfügbaren Röntgenstrahlung genutzt. <br>Im ersten Teil der Arbeit werden Röntgen-Diffraktometrie und -Topographie zu einer Untersuchungsmethode kombiniert, mit der die makroskopische Krümmung von Halbleiter-Wafern ebenso wie ihre mikroskopische Defektstruktur abgebildet werden kann. Der zweite Teil ist der Untersuchung von epitaktisch gewachsenen und geätzten Oberflächengittern mit Abmessungen im Submikrometer-Bereich gewidmet. Die unterschiedlichen Gitterkonstanten der beteiligten Halbleitermaterialien führen zu einem inhomogenen Verzerrungsfeld in der Probe, das sich im Röntgenbild durch eine charakteristische Verformung des Beugungsmusters in der Umgebung der Bragg-Reflexe äussert. Die Analyse der experimentell gemessenen Beugungsmuster geschieht mit Hilfe eines neu entwickelten Simulationsverfahrens, das Elastizitätstheorie und eine semi-kinematische Röntgenbeugungstheorie miteinander verbindet. Durch quantitativen Vergleich der Simulationsergebnisse mit den Messdaten kann auf den genauen Verlauf des Verzerrungsfeldes in den Proben zurückgeschlossen werden. Dieses Verfahren wird erfolgreich auf verschiedene Halbleiter-Probensysteme angewendet, und schliesslich auch auf die Untersuchung von akustischen Oberflächenwellen in Halbleiterkristallen übertragen. / This thesis presents newly developed X-ray methods which can be used to characterize in detail the state of distortion of the crystal lattice in semiconductor wafers, devices and nanostructures. The methods use the extraordinary properties of the X-rays available from modern synchrotron sources such as the ESRF (Grenoble). <br>In the first part of the thesis, X-ray diffractometry and X-ray topography are combined into a new method, called X-ray rocking curve imaging, which allows to image the macroscopic curvature of semiconductor wafers as well as the underlying microscopic defect structure. The second part of the thesis deals with the investigation of epitaxially grown and subsequently etched semiconductor gratings with lateral periods below the micrometer. The lattice mismatch between the different materials used in heteroepitaxy leads to a non-uniform strain field in the sample, which is reflected in a characteristic distortion of the X-ray diffraction pattern around each Bragg peak. The experimental data are evaluated with the help of a newly developed simulation procedure which combines elasticity theory with a semi-kinematical theory of X-ray diffraction. From a quantitative comparison of measured and simulated data the detailed shape of the strain field in the samples can be deduced. This procedure is used successfully for the structural characterization of different types of semiconductor gratings, and is finally applied also to the investigation of surface acoustic waves in crystals.

I den här avhandlingen visas hur lasrar och optiska parametriska oscillatorer (OPO:er) kan styras spektralt med hjälp av volymbraggitter. Volymbraggitter utgörs av ett periodiskt varierande brytningsindex som skrivits i ett fototermorefraktivt glas. Gittret reflekterar därmed en specifik våglängd som bestäms av perioden hos modulationen, och kan tillverkas med smal bandbredd och hög reflektans beroende på modulationens längd och styrka. En teoretisk modell har utvecklats för reflektiva volymbraggitters egenskaper om den infallande strålen har en större vinkelspridning än gittrets vinkeltolerans. Detta kan bl.a. inträffa i en laserkavitet där gittret används vid snett infall, och en teoretisk beskrivning är därför ett viktigt redskap för att kunna designa sådana lasrar. Spektral kontroll av ett antal fasta tillståndslasrar med hjälp av volymbraggitter har i försök påvisats, och lasern har därvid både kunnat avstämmas spektralt samtidigt som en avsmalnad spektral bandbredd erhållits. Lasern kan göras väldigt enkel genom att byta ut en av kavitetsspeglarna mot gittret. Tack vare gittrets goda spektrala urvalsmekanism kan lasern låsas var som helst i förstärkningsspektrumet. De tekniker och lasrar som demonstrerats experimentellt är följande: Lasring i en enda longitudinell mod erhölls både för en diodpumpad ErYb:glas-laser vid 1553 nm med ca 10 mW:s effekt och 90 kHz linjebredd samt för en diodpumpad Nd:GdVO4-laser vid 1066 nm med 0.85 W:s effekt. Lasrarnas våglängd kunde avstämmas över större delen av gittrets bandbredd på ca. 30 GHz. Genom att bygga Nd:GdVO4-lasern med en monolitisk kavitet kunde även en spektralt synnerligen stabil laser erhållas med under 40 MHz bandbredd. Tillämpningar för dessa lasrar finns både inom spektroskopi samt som källor för intrakavitetsfördubbling till synliga våglängder. Genom att använda gittret som inkopplingsspegel går det även att framställa lasrar med en väldigt låg kvantdefekt, som därför får minskad värmeutveckling i lasermediet. Detta medger i sin tur att lasrar med höga medeleffekter kan konstrueras, som kan användas bl.a. för olika former av materialbearbetning. I detta arbete har lasrar med låg kvantdefekt byggts med Yb:KYW som laserkristall; både en laser vid 998 nm på 3.6 W som diodpumpades vid 982 nm och med en bandbredd på 10 GHz, samt en laser vid 990 nm på 70 mW som pumpades av en Ti:safir-laser vid 980 nm. Om volymbraggittret används vid snett infall kan den reflekterade våglängden avstämmas genom att gittret roteras. Denna princip användes i en diodpumpad Yb:KYW-laser till att erhålla en brett avstämbar laservåglängd mellan 996 nm och 1048 nm med en maximal effekt på 3 W och med 10 GHz bandbredd. Genom att placera gittret i en retroreflektor kunde avstämningen göras utan att kaviteten behövde linjeras om. En laser som denna kan exempelvis användas för olika typer av materialkarakterisering och spektroskopi. Med optiska parametriska oscillatorer (OPO:er) kan laserljus omvandlas till nya våglängder. Därmed kan OPO:er användas som koherenta ljuskällor där inga effektiva lasrar existerar. OPO-processen kan göras effektiv om en pulsad pump används, och den genererade våglängden kan enkelt styras med hjälp av periodiskt polade (PP) icke-linjära kristaller, såsom PP-KTiOPO4, som användes i detta arbete. En nackdel med OPO:er är att i allmänhet är den genererade signalen tämligen spektralt bredbandig. Signalens bandbredd kan dock avsmalnas betydligt om ett spektralt filter såsom ett volymbraggitter används. Genom att byta ut en av speglarna i OPO-kaviteten mot gittret kan utformningen av OPO:n göras väldigt enkel. I en OPO med en signalvåglängd på 975 nm kunde en avsmalning av bandbredden till 50 GHz påvisas med hjälp av ett braggitter. Detta motsvarar 20 gångers minskning jämfört med om en konventionell spegel används. Som mest erhölls en pulsenergi på 0.34 mJ i signalen. Genom att rotera gittret kunde våglängden avstämmas 21 THz. För att förenkla avstämningen konstruerades även en OPO med gittret i en retroreflektor, samtidigt som kaviteten var av ringtyp. I denna OPO vid en våglängd på 760 nm och med en pulsenergi i signalen på upp till 0.42 mJ erhölls en bandbredd på 130 GHz och ett avstämningsområde på 2.6 THz. Slutligen har en OPO vid 1 µm konstruerats med ett gitter med en transversellt varierande period, s.k. chirp. Därigenom kan våglängden avstämmas väldigt enkelt genom att bara flytta gittret transversellt. En tillämpning av dessa OPO:er är såsom ljuskällor i olika typer av laserbaserade sensorer, i vilka en specifik och stabil våglängd erfordras. Dessutom kan de smalbandiga OPO:erna användas som första steg i ickelinjära processer i flera steg. Smal bandbredd är då viktig för effektiviteten i den påföljande ickelinjära omvandlingen i nästa steg. / The object of this thesis is to explore the usage of reflective volume Bragg gratings in photo-thermo-refractive glass for spectral control of solid-state lasers and optical parametric oscillators, to build tunable and narrowband coherent light-sources. In order to provide a design tool for use of reflective volume Bragg gratings in laser cavities, a theory was developed that describes the performance of the gratings if the incident beam has finite width with an angular spectrum that is comparable to the grating's angular acceptance bandwidth. Spectral control was demonstrated in a number of cw solid-state lasers, in terms of narrow bandwidth and tunable wavelength, by use of a volume Bragg grating. The design could be made very simple by replacing one of the cavity mirrors with the grating. Thanks to the grating's strong spectral selectivity, the lasers could be locked anywhere in the gain spectrum, while the laser bandwidth was substantially narrowed. In particular, the following lasers were demonstrated: Single-longitudinal-mode lasing in ErYb:glass at 1553 nm with 90 kHz linewidth and in Nd:GdVO4 at 1066 nm with a linewidth below 40 MHz. Very low quantum defect in Yb:KYW lasers, diode-pumped at 982 nm and lasing at 998 nm with 10 GHz bandwidth, as well as Ti:sapphire-pumped at 980 nm and lasing at 990 nm. An Yb:KYW laser that was widely tunable from 996 nm to 1048 nm with 10 GHz bandwidth. In nanosecond pulsed optical parametric oscillators (OPOs) based on periodically poled KTiOPO4, narrowband operation and a tunable wavelength were demonstrated with a volume Bragg grating as a cavity mirror. At a signal wavelength of 975 nm, the bandwidth was 50 GHz, a reduction by 20 times compared to using a conventional mirror. A tuning range of 21 THz was also demonstrated. In another OPO at a signal wavelength of 760 nm, a ring-cavity design was demonstrated to provide convenient tuning. A tuning range of 2.6 THz and a bandwidth of 130 GHz was shown. Also, narrowband operation and tuning in an OPO around 1 µm was demonstrated by use of a transversely chirped Bragg grating. / QC 20100813

The use of composite materials in industrial applications such as aeronautical, aerospace or wind energy production has greatly increased in recent decades. Due to their inherent properties, these materials allow lighter, larger and more resistant structures. However, the use of composite materials for components or structures with highly stringent requirements, is hampered by the lack of knowledge of their reliability. In this thesis, some fundamental aspects about the use of fibre Bragg grating (FBG) sensors for internal strain measurements in composite laminates are discussed. In addition, a highly accurate method for locating the crack tip position in mixed-mode delamination growth has been presented. Finally, an experimental application of FBGs to dynamic measurements in mode I fatigue test has been performed / L’ús de materials compostos en aplicacions de caràcter industrial com per exemple l’aeronàutica, aeroespacial o la de producció d’energia eòlica, ha crescut exponencialment durant les últimes dècades. Degut a les seves extraordinàries propietats, l’ús d’aquests materials permet la construcció d’estructures més lleugeres, grans i resistents, tot i que el seu ús en components d’alta responsabilitat estructural està limitat per la manca de coneixement en relació a la seva fiabilitat estructural. En aquesta tesi es discuteixen alguns aspectes significants sobre l’ús de FBGs per a mesurar camps de deformació en l’interior de laminats de material compòsit, s’ha analitzat també la capacitat de localització de la punta d’una esquerda en creixement de mode mixt i per últim s’ha desenvolupat una aplicació pràctica dels FBG en temps real en assaigs a fatiga en mode I

The subject of this thesis is the exploration of new concepts for compact solid-state lasers in the visible and near-infrared spectral range using new components such as volume Bragg gratings for wavelength stabilisation and wavelength tuning. Also single-walled carbon nanotubes for mode-locking and Q-switching of lasers have been studied.We have developed a new method for the tuning of solid-state lasers by replacing a dielectric mirror with a transversally chirped volume Bragg grating, which allows smooth wavelength tuning without additional elements inside the laser cavity. The result is a more compact laser, since the tuning mechanism and output coupler are incorporated in one component. Another benefit is an increased efficiency, since additional elements inside the cavity will always add to the total loss of the laser. This has been demonstrated for a broadband ytterbium laser around 1 µm and a single-longitudinal-mode Nd:YVO4 laser around 1.06 µm. A volume Bragg grating has also been used to construct an efficient, narrow-linewidth ytterbium fiber laser and the employment of a volume Bragg gratingas the pump mirror of a solid-state laser for frequency-doubling has been investigated. Both lasers represent a practical solution, eliminating the use of additional intracavity elements. Second-harmonic generation is an efficient way to access the visible spectral range using diode-pumped solid-state lasers. However, these lasers can suffer from large amplitude fluctuations, which has been analyzed in more detail for an optically-pumped semiconductor disk-laser and a volume Bragg grating locked ytterbiumlaser. The control of those amplitude fluctuations is very important, since many applications like fluorescence microscopy require a laser with a constant output power and as little noise as possible. In addition to this, we have demonstrated, that saturable absorbers based on quan-tum dots and carbon nanotubes can be used to mode-lock compact laser at a wavelength around 1.03 µm. Those lasers have many interesting applications incommunications, clock generation, metrology and life sciences. / <p>QC 20130507</p>

The interaction of light and matter at nanoscale is the subject of study of this dissertation. Particularly, the coupling of light to surface plasmons and their applications in the fields of spectroscopy and sensing is the focus of this work. In terms of spectroscopy, the simple reason of using light to study the chemical structures of different materials is the fact that the energy of light lies in the range of vibrational and electronic transitions of matter. Further, the ability to squeeze light to subwavelength dimensions opens up new possibilities of designing nano-optical devices. In this work we explore surface plasmons for two major applications: (i) Directivity enhanced Raman spectroscopy and (ii) Chemical/biological sensing. Here a new enhancement phenomenon has been demonstrated experimentally in regards to Raman spectroscopy. Typically, Raman enhancement is considered in terms of local fields only. Here we show the use of directive nanoantennas to provide additional enhancement of two orders of magnitude. The nanoantenna design is optimal in the sense that almost all of the scattered light is coupled into the numerical aperture of the collecting lens. It is shown that the additional enhancement from directivity pushes the sensitivity to single molecule regime. Further, the out of plane radiation and simplicity of the design makes it an ideal candidate for use with typical commercial microscope setups. Extra ordinary transmission through nanohole arrays in metallic films is studied for refractive index sensing. Bulk resolution of 6×10-7 is demonstrated by optimizing array dimensions, wavelength of operation, noise reduction and consideration of sensitivity of the detecting CCD camera. Self-assembled nanostructures are investigated for spectroscopic applications. Time dependent studies of nanorods assembled in end-to-end and side-by-side configurations are conducted. The end-to-end configuration results in higher local field enhancements whereas; the side-by-side configuration shows a reduction in local fields because of the cancellation of radial field components between the neighbouring nanorods. It should be noted that higher fields are desirable for Raman spectroscopy. Grating structures have been analysed using reduced coupled mode theory. In most cases, only three lowest order modes prove to be sufficient for accurate description of the system response. Here we present design guidelines for broadband operation and optimization of high quality factor resonators. Finally the complex reflection coefficient from arbitrary terminated nanorods has been investigated. Phase of reflection plays an important role in the determination of resonance wavelength of nanoantennas. It is shown that the localized surface plasmon resonance of nanoparticles can be considered in terms of propagating surface plasmons along a nanorod of similar geometry where the length of the nanorod approaches zero accompanied with π degrees of phase of reflection. The contributions made in this work can prove useful in the fields of analytical chemistry and biomedical sensing. The directive nanoantenna can find applications in a number of areas such as light emitting devices, photovoltaics, single photon sources and high resolution microscopy. Our work related to EOT based sensing is already approaching the resolution of commercially available refractive index sensors with the added advantage of multiplexed detection. / Graduate