Dissertations / Theses on the topic 'Photonics, Nanostructures'

Quantum dot structures of InAs(Sb)/InGaAs/InP designed as easy to fabricate, low cost "mid-IR emitting lasers, have been spectroscopically characterised using temperature and power dependent photoluminescence. These structures have been simulated using a truncated pyramid structure in the Nextnano software package. The results show that the observed experimental data is the result Of a . bimodal dot distribution in both samples. In the InAs case, the bimodal behaviour is the result of varying width dots (35nm and 38.5nm). In the InAsSb case the dot groups were calculated to contain - 10% and zero antimony, indicating difficulties during the growth process. Additionally the InAs dots were found to have a dominant radiative recombination process, while the InAsSb dots were found to be affected by a defect related recombination process. It is suggested this is a result of increased defects formed by the larger lattice mismatch. InAs/InAsSb superlattice structures have potential as mercury cadmium telluride (MCT) alternative mid-IR photo-detectors, and are predicted to not suffer from Ga-related defect recombination as other superlattice structures. High pressure techniques and modelling were used to probe the defect level in these structures. High pressure, low temperature photoluminescence experiments were performed using the sapphire ball cell to move the conduction / band minima up in energy until overlap with the predicted defect level state was achieved. This resulted in a decrease in the measured integrated intensity of the sample due to carriers recombining via the defect states. Additionally power dependent measurements at high and low pressure were performed and an observed shift from radiative to defect dominated recombination was observed. This provides the first experimental evidence of a defect level positioned above the conduction band edge. This means that SRH recombination in the forbidden band gap will not be a contributing factor to the dark currents in InAs/InAsSb superlattice photo -detectors showing their promise for low dark current mid-IR detectors.

Photonic crystals (PCs), consisting of a periodic pattern of variations in the material properties, are one of the platforms proposed as synthetic optical materials to meet the need for optical materials with desired properties. Recently, applications based on dispersive properties of the PCs have been proposed in which PCs are envisioned as optical materials with controllable dispersive properties. Unlike the conventional use of PCs to achieve localization, in these new applications propagation inside the photonic crystal is studied, and their dispersive properties are utilized. Among these applications, the possibility of demultiplexing light using the superprism effect is of particular interest. Possibility of integration and compactness are two main advantages of PC-based wavelength demultiplexers compared to other demultiplexing techniques, for applications including compact spectrometers (for sensing applications), demultiplexers (for communications), and spectral analysis (for information processing systems). I develop the necessary simulation tools to study the dispersive properties of photonic crystals. In particular, I will focus on superprism-based demultiplexing in PCs, and define a phenomenological model to describe different effects in these structures and to study important parameters and trends. A systematic method for the optimization and design of these structures is presented. Implementation of these structures is experimentally demonstrated using the devices fabricated in a planar SOI platform based on designed parameters. In the next step, different approaches to improve the performance of these devices (for better resolution and lower insertion loss) are studied, and extension of the concepts to other material platforms is discussed.

Le but de cette thèse est d'adopter une approche hybride par la combinaison des méthodes de lithographie ascendantes et descendantes pour la fabrication de nanostructures avec des propriétés structurales et optiques d’intérêt. Cette approche multidisciplinaire est un domaine vaste ou les combinaisons prometteuses sont nombreuses mais restent inexplorées jusqu'à présent. Ces travaux vont s’intéresser aussi bien à la chimie des matériaux qu'aux techniques de nanofabrication de salle blanche afin d'apporter des solutions pratiques aux problèmes actuels rencontrés en nanofabrication. Plus précisément, nous nous intéressons à l’étude de certaines techniques de lithographies (en particulier à la nano-impression) et démontrons la possibilité d’améliorer la cadence de fabrication en obtenant des nanostructures sur une échelle de plusieurs centimètres carrés. Les nanostructures fabriquées sont principalement utilisées comme résonateurs de Mie pour leurs propriétés optiques et leur capacité à modifier la lumière incidente. Des démonstrateurs de plusieurs millimètres carrés sont réalisés et montrent des propriétés optiques intéressantes soulignant la viabilité de notre approche
The scope of this thesis is to adopt a hybrid approach through the synergetic combination of bottom-up and top-down lithography methods to fabricate nanostructures with interesting structural and optical properties. This multidisciplinary approach is a vast fruitful field where many combinations are promising but remains unexplored so far. By taking interest in, and bringing together, both materials chemistry and clean-room nanofabrication techniques, this work tries to find practical solutions to tackle some of the current challenges in nanofabrication. In details, we focus on the study of selected lithography techniques (in particular nanoimprint) and demonstrate the possibility to increase the fabrication throughput and obtain nanostructures on a centimeter scale. The nanofabricated structures are then mainly used as Mie resonators for their optical properties and their ability to modify incoming light. Demonstrators of several millimeters are produced and are shown to exhibit interesting optical properties; emphasizing the feasibility of our approach

In this work, I studied the hybrid system based on self-assembled guanosine crystal (SAGC) conjugated to wide-bandgap semiconductor gallium nitride (GaN). Guanosine is one of the four bases of DNA and has the lowest oxidation energy, which favors carrier transport. It also has large dipole moment. Guanosine molecules self-assemble to ribbon-like structure in confined space. GaN surface can have positive or negative polarity depending on whether the surface is Ga- or N-terminated. I studied SAGC in confined space between two electrodes. The current-voltage characteristics can be explained very well with the theory of metal-semiconductor-metal (MSM) structure. I-V curves also show strong rectification effect, which can be explained by the intrinsic polarization along the axis of ribbon-like structure of SAGC. GaN substrate property influences the properties of SAGC. So SAGC has semiconductor properties within the confined space up to 458nm. When the gap distance gets up to 484nm, the structure with guanosine shows resistance characteristics. The photocurrent measurements show that the bandgap of SAGC is about 3.3-3.4eV and affected by substrate properties. The MSM structure based on SAGC can be used as photodetector in UV region. Then I show that the periodic structure based on GaN and SAGC can have photonic bandgaps. The bandgap size and the band edges can be tuned by tuning lattice parameters. Light propagation and emission can be tuned by photonic crystals. So the hybrid photonic crystal can be potentially used to detect guanosine molecules. If guanosine molecules are used as functional linker to other biomolecules which usually absorb or emit light in blue to UV region, the hybrid photonic crystal can also be used to tune the coupling of light source to guanosine molecules, then to other biomolecules.

Plasmonic resonances are characterized by enhanced optical near field and subwavelength power confinement. Light is not only scattered but also simultaneously absorbed in the metal nanostructures. With proper structural design, plasmonic-enhanced light absorption can generate nanoscopically confined heat power in metallic nanostructures, which can even be temporally modulated by varying the pump light. These intrinsic characters of plasmonic nanostructures are investigated in depth in this thesis for a range of materials and nanophotonic applications.   The theoretical basis for the photothermal phenomenon, including light absorption, heat generation, and heat conduction, is coherently summarized and implemented numerically based on finite-element method. Our analysis favours disk-pair and particle/dielectric-spacer/metal-film nanostructures for their high optical absorbance, originated from their antiparallel dipole resonances.   Experiments were done towards two specific application directions. First, the manipulation of the morphology and crystallinity of Au nanoparticles (NPs) in plasmonic absorbers by photothermal effect is demonstrated. In particular, with a nanosecond-pulsed light, brick-shaped Au NPs are reshaped to spherical NPs with a smooth surface; while with a 10-second continuous wave laser, similar brick-shaped NPs can be annealed to faceted nanocrystals. A comparison of the two cases reveals that pumping intensity and exposure time both play key roles in determining the morphology and crystallinity of the annealed NPs.   Second, the attempt is made to utilize the high absorbance and localized heat generation of the metal-insulator-metal (MIM) absorber in Si thermo-optic switches for achieving all-optical switching/routing with a small switching power and a fast transient response. For this purpose, a numerical study of a Mach-Zehnder interferometer integrated with MIM nanostrips is performed. Experimentally, a Si disk resonator and a ring-resonator-based add-drop filter, both integrated with MIM film absorbers, are fabricated and characterized. They show that good thermal conductance between the absorber and the Si light-guiding region is vital for a better switching performance.   Theoretical and experimental methodologies presented in the thesis show the physics principle and functionality of the photothermal effect in Au nanostructures, as well as its application in improving the morphology and crystallinity of Au NPs and miniaturized all-optical Si photonic switching devices.

QC 20140331

Thesis (Ph. D.)--West Virginia University, 2001
Title from document title page. Document formatted into pages; contains vii, 112 p. : ill. (some col.) Includes abstract. Includes bibliographical references.

This thesis focuses on the heterogeneous growth optimization of III-V nanostructures on Si (001) substrate displaying a miscut toward [110]. The main purpose concerns the integration of efficient light sources on Si substrate for high-speed optical interconnects inter-and intra-chip, as a cornerstone for the development of optoelectronic integrated circuits (OEIC).First, this study focuses on the optimisation of nitrogen incorporation in GaPN on GaP(001) substrate, while reachingthe lattice-matching condition with Si. This study is also interesting for the growth of any GaPN-based dilute nitridecompounds, such as GaAsPN, which are very attractive for long wavelength laser applications and high-efficiency photovoltaic applications on Si substrates. In a second step, we studied the growth of an active layer based on (In,Ga)As quantum dots (QD) on GaP (001) substrate. These QD display a high density and good uniformity in size. Room temperature photoluminescence is also obtained on these QD, which is very promising for the fabrication of integrated optoelectronic sources on a silicon substrate. In the third part, this study focuses on the homoepitaxial growth of Si by UHV/CVD necessary to bury residual contaminants initially present on the Si surface, and to obtain a Si surface suitable for the subsequent heteroepitaxial growth of optimal structural quality GaP layer. This includes the formation of double atomic steps, by step bunching and favors by the substrate miscut, in order to limit the structural defects. Finally, the GaP/Si interface is optimized, while obtaining a flat GaP surface and a minimum defects density. A methodology to quantify the structural defects (anti-phase domains, micro-twins) by X-ray diffraction using Synchrotron and laboratory sources is presented. This study reveals an anisotropic behavior of the micro-twins, linked to the miscut direction of the Si substrate, and a dramatic reduction of the micro-twins density at high growth temperature. The growth of thin GaP layers on Si substrates, with thickness less than the critical one and obtained with a purposely dedicated growth cluster composed of a Si UHV/CVD chamber connected under UHV with a III-V MBE chamber, shows a significant reduction of the structural defects and provides a GaP/Si pseudo-substrate with a flat surface suitable for subsequent growth of efficient light sources.

In this thesis innovative plasmonic nanostructures have been studied under many aspects, from the synthesis to the characterization and finite elements modeling. We focused on two kinds of ordered nanostructures: (i) those exhibiting bidimensional (2D) translational invariance and (ii) those possessing autosimilarity and fractal character. Three kinds of nanostructures characterized by 2D periodicity have been analyzed: nanoprism arrays (NPA), nanohole arrays (NHA) and quasishell arrays (QSA), whose building blocks are, respectively, metallic prisms with triangular-like base, holes passing through a metal thin film and metallic non-closed shells around a dielectric core. The first kind is the base for biosensors, and in this case an optimization study has been performed to maximize sensivity. The second one is the key for a fine control of the emission from excited Erbium ions, which overcomes the previous results obtained without nano-patterning. The third one is based on a novel approach to bi-metallic nanostructures fabrication, enabling the realization of plasmonic and magneto-plasmonic materials. The patterning at nano scales has been made cost-effective, as all these periodic systems are based on a cheap synthesis technique. Finally, nanostructures showing scale invariance, fractals, have been synthesized and thoroughly studied, both experimentally and with simulations. As a result, a universal role of correlation has been recognized in these plasmonic systems. Overall, this thesis gives insights on the physics underlying the plasmonic response of nanostructures which base their outstanding properties on symmetry, either on scaling or on translation.
In questa tesi nanostrutture plasmoniche innovative sono state studiate sotto molteplici aspetti, a partire dalla sintesi fino alla caratterizzazione e alla modellizazione ad elementi finiti. L’attenzione è stata focalizzata su due tipi di nanostrutture ordinate: (i) quelle che mostrano invarianza traslazionale bidimensionale (2D) e (ii) quelle che hanno autosimilarità e carattere frattale. Tre tipi di nanostrutture caratterizzate dalla periodicità 2D sono state analizzate: matrici di nanoprismi, matrici di nanobuchi e matrici di gusci quasi chiusi, i cui elementi di base sono, rispettivamente, prismi metallici a base triangolare, buchi che attraversano strati sottili di metallo e gusci metallici non chiusi attorno a un nucleo dielettrico. Il primo tipo è la base per dei biosensori, e in questo caso uno studio di ottimizzazione è stato compiuto per massimizzare la sensibilità. Il secondo tipo è la chiave per il controllo fine dell’emissione da ioni di Erbio eccitati, e il risultato supera i precedenti, ottenuti senza nanostrutturazione. Il terzo tipo è basato su di un nuovo approccio per la fabbricazione di nanostrutture bi-metalliche, consentendo la produzione di materiali plasmonici e magnetoplasmonici. La strutturazione alla nanoscala è stata portata avanti in modo economicamente vantaggioso, essento tutti e tre i sistemi periodici basati su di una tecnica poco costosa di sintesi. Infine, nanostrutture che mostrano invarianza di scala, frattali, sono state sintetizzate e studiate meticolosamente, sia sperimentalmente che con simulazioni. Come risultato, il ruolo universale della correlazione è stato identificato in questo tipo di sistemi plasmonici. Complessivamente, la presente tesi fornisce una comprensione della fisica alla base della risposta plasmonica delle nanstrutture che basano le loro notevoli proprietà sulle simmetrie, siano esse di scala o per translazione.

The propagation of light and its interaction with metallic nanostructures at the scale that is smaller than the wavelength of light (subwavelength) is an interesting phenomenon. In recent years, confining light at a subwavelength scale by very small metallic nanoparticles, such that quantum effects cannot be neglected, has generated interest in the scientific community. The light-matter interactions at this level require a careful quantum mechanical treatment to be correctly characterized, hence evolving in a new field named Quantum Plasmonics. In metallic nanostructures with sizes below 10 nm, the collective and coherent oscillations of electrons (plasmon resonance), cannot be described by classical models since the quantum-mechanical effects start dominating and become relevant with changing the plasmons oscillation frequency. Such changes have so far been poorly understood and the experimental measurements that have been carried out, have struggled to be correctly interpreted. Therefore, a quantum model of metal permittivity is required to understand the size-dependent optical properties of very small nanostructures. Here we present the nonlocal quantum model, obtained by applying the Wigner equation with the collision term in the kinetic theory of metals. Our results suggest that the probability of finding electrons at higher energy levels increases in the excitation of quantum plasmons, since their wave functions overlap, and therefore, the quantum tunnelling effect increases. The dispersion relation, damping rate, and decay length of surface and bulk plasmon resonances are investigated in thin metal film slabs and small silver nanoparticles with the various diameter down to atomic size and plasmon wave functions are shown for solutions of infinite quantum well at various quantum levels.

Light interaction with matter has long been an area of interest throughout history, spanning many fields of study. In recent decades, the investigation of light-matter interactions with nanostructures has become an intense area of research in the field of photonics. Metallic nanostructures, in particular, are of interest due to the interesting properties that arise when interacting with light. The properties are a result of the excitation of surface plasmons which are the collective oscillation of the conduction electrons in the metal. Since the conduction electrons can be thought of as harmonic oscillators, they are quantized in a similar fashion. Just as a photon is a quantum of oscillations of an electromagnetic field, the plasmon is a quantum of electron oscillations of a metal. There are three types of plasmons: 1. Bulk plasmons, also called volume plasmons, are longitudinal density fluctuations which propagate through a bulk metal with an eigenfrequency of ?_p called the plasma frequency. 2. Localized surface plasmons are non-propagating excitations of the conduction electrons of a metallic nanoparticle coupled to an electromagnetic field. 3. Surface plasmon polaritons are evanescent, dispersive propagating electromagnetic waves formed by a coupled state between a photon and the excitation of the surface plasmons. They propagate along the surface of a metal-dielectric interface with a broad spectrum of eigenfrequencies from ?=0 to ?= ?_p??2. Plasmonics is a subfield of photonics which focuses on the study of surface plasmons and the optical properties that result from light interacting with metal films and nanostructures on the deep subwavelength scale. In this thesis, plasmonic nanostructures are investigated for optical waveguides and other nanophotonic applications through computational simulations primarily base on electrodynamic theory. The theory was formulated by several key figures and established by James Clerk Maxwell after he published a set of relations which describe all classical electromagnetic phenomena, known as Maxwell's equations. Using methods based on Maxwell's equations, the optical properties of metallic nanostructures utilizing surface plasmons is explored. In Chapter 3, light propagation of bright and dark modes of a partially and fully illuminated silver nanorod is investigated for waveguide applications. Then, the origin of the Fano resonance line shape in the scattering spectra of a silver nanorod is investigated. Next, in Chapter 4, the reflection and transmission of a multilayer silver film is simulated to observe the effects of varying the dielectric media between the layers on light propagation. Building on the multilayer film work, metal-insulator-metal waveguides are explored by perforating holes in the bottom layer of a two layer a silver film to investigate the limits of subwavelength light trapping, confinement, and propagation. Lastly, in Chapter 5, the effect of surface plasmons on the propagation direction of electromagnetic wave around a spherical silver nanoparticle which shows an effective negative index of refraction is examined. In addition, light manipulation using a film of silver prisms with an effective negative index of refraction is also investigated. The silver prisms demonstrate polarization selective propagation for waveguide and optical filter applications. These studies provide insight into plasmonic mechanisms utilized to overcome the diffraction limit of light. Through better understanding of how to manipulating light with plasmonic nanostructures, further advancements in nanophotonic technologies for applications such as extremely subwavelength waveguides, sensitive optical detection, optical filters, polarizers, beam splitters, optical data storage devices, high speed data transmission, and integrated subwavelength photonic circuits can be achieved.
Ph.D.
Doctorate
Chemistry
Sciences
Chemistry

Actualment, un dels reptes en l’àmbit de la manipulació de la llum a la nanoescala és la transició del laboratori a aplicacions reals. Tot i el gran potencial demostrat per algunes estructures fotòniques per a incrementar la eficiència de instruments optoelectrònics, la seva implementació de d’aquestes a dispositius de mercat sovint es obstruïda per la necessitat d’usar tècniques de fabricació poc escalables i d’alt cost. Aquesta tesis està dedicada al disseny i implementació de estratègies de manipulació de la llum per a millorar la eficiència en la recol·lecció d’energia de plaques solars i fotodetectors, així com la millora de la emissió en dispositius d’il·luminació, mitjançant mètodes de nanoestructuració escalables com la nano-litografia suau. Aquesta tècnica té la capacitat de produir patrons i estructures amb una resolució de pocs nanòmetres amb gran fidelitat en àrees grans. A més a més, és compatible amb el processament a gran escala mitjançant el sistema de impressió en cadena “roll to roll” (carret-a-carret). També es tracta d’una tecnologia molt versàtil, ja que permet l’ús de diferents tipus de substrats, és poc invasiva i generalment pot ser introduïda en el esquema de fabricació sense haver de modificar cap pas. Amb l’ajuda d’aquesta tècnica de nanofabricació, explorem una varietat de arquitectures fotòniques i les diferents ressonàncies fotòniques que les fan especials. Entre aquestes darreres podem trobar ressonàncies de Mie, modes de Brewster i modes de cristall fotònic, que proveiran al sistema amb una major interacció llum-matèria a la capa activa del dispositiu, podent-ne millorar les seves capacitats òptiques. Primer, hem desenvolupat una estratègia per aconseguir una absorció optima de banda ample en semiconductors ultra-fins, amb menys de 100 nm de gruix, per a totes les energies per sobre de la seva energia de banda prohibida. La sinèrgia de les fortes ressonàncies d’interferència de capes fines presents i els modes del cristall fotònic de l’estructura (amb un alt índex de refracció) fan que l’estructura assoleixi fins a un 81% d’absorció en una ampli rang de longituds d’ona (de 400 a 1500 nm). En segon lloc, hem combinat la litografia suau amb la deposició química de vapor (CVD en anglès) per obtenir una matriu de semiesferes de silici sobre de una guia d’ones d’alt índex de refracció. Hem estudiat les ressonàncies de Mie característiques del substrat, com hibriden amb modes quasi-guiats de la guia d’ones i com això afecta al camp proper de la metasuperfície. Hem anat un pas més enllà estudiant la com la modificació dels paràmetres de disseny de l’estructura afecta les ressonàncies esmentades. Finalment, n’hem demostrat una possible aplicació com a substrat per a incrementar la emissió de llum per part de una molècula emissora. En la tercera part de la tesi, ens hem enfocat en la implementació de estructures de cristall fotònic bidimensional a tres dispositius diferents per a la millora de la seva eficiència. En particular, millorem la eficiència en la recol·lecció de fotons d’infraroig proper en cèl·lules solars de punts quàntics col·loïdals (PbS) i en fotodetectors orgànics (P3HT: PC60BM i PBTTT: PC70BM), i millorem l’emissió de llum de capes de nanofòsfors (nanocristalls de GdVO4:Eu3+). Hem desenvolupat sistemes fotònics adaptats a cada cas i hem fet una caracterització òptica i electrònica de tots els dispositius. La nanoestructuració en forma de cristall fotònic bidimensional proveeix a les capes actives amb propietats de guies d’ona ressonants, millorant les seves propietats de confinament de la llum en les longituds d’ona desitjades, demostrant així la possibilitat d’implementar les arquitectures.
Actualmente, uno de los retos en el ámbito de la manipulación de la luz a la nanoescala es la transición del laboratorio a aplicaciones reales. A pesar del gran potencial demostrado por algunas estructuras fotónicas para incrementar la eficiencia de instrumentos optoelectrónicos, su implementación en dispositivos de mercado muchas veces es obstruida por la necesidad de utilizar técnicas de fabricación poco escalables y de alto coste. Esta tesis está dedicada al diseño e implementación de estrategias de manipulación de la luz para mejorar la eficiencia en la recolección de energía de placas solares y fotodetectores, así como la mejora de la emisión en dispositivos de iluminación, mediante métodos de nanoestructuración escalables como la nano-litografía suave. Esta técnica tiene la capacidad de producir patrones y estructures con una resolución de pocos nanómetros con gran fidelidad en áreas grandes. Encima, es compatible con el procesamiento a gran escala mediante el sistema de impresión en cadena “roll-to-roll” (carrete-a-carrete). También se trata de una tecnología muy versátil, puesto que permite el uso de diferentes tipos de sustratos, es poco invasiva y generalmente puede ser introducida en el esquema de fabricación sin tener que modificar ningún paso. Con la ayuda de esta técnica de nanofabricación, exploramos una variedad de arquitecturas fotónicas y las diferentes resonancias fotónicas que las hacen especiales. Entre estas últimas podemos encontrar resonancias de Mie, modos de Brewster y modos de cristal fotónico, que proveerán al sistema con una mayor interacción luz-materia a la capa activa del dispositivo, mejorar sus capacidades ópticas. Primero, hemos desarrollado una estrategia para conseguir una absorción óptima de banda ancha en semiconductores ultra-finos, con menos de 100 nm de grosor, para todas las energías por encima de su energía de banda prohibida. La sinergia de las fuertes resonancias de interferencia de capas finas presentes y los modos del cristal fotónico de la estructura (con un alto índice de refracción) hacen que la estructura logre hasta un 81% de absorción en un amplio rango de longitudes de omda (de 400 a 1500 nm). En segundo lugar, hemos combinado la litografía suave con la deposición química de vapor (CVD en inglés) para obtener una matriz de semiesferas de silicio sobre de una guía de ondas de alto índice de refracción. Hemos estudiado las resonancias de Mie características del sustrato, como hibridan con modos casi-guiados de la guía de olas y como esto afecta en el campo próximo de la metasuperfície. Hemos ido un paso más allá estudiando como la modificación de los parámetros del diseño de la estructura afecta a las resonancias mencionadas. Finalmente, hemos demostrado una posible aplicación como sustrato para incrementar la emisión de luz por parte de una molécula emisora. En la tercera parte de la tesis, nos hemos enfocado en la implementación de estructuras de cristal fotónico bidimensional a tres dispositivos diferentes para la mejora de su eficiencia. En particular, mejoramos la eficiencia en la recolección de fotones de infrarrojo próximo en células solares de puntos cuánticos coloidales (PbS) y en fotodetectores orgánicos (P3HT: PC60BM y PBTTT: PC70BM), y mejoramos la emisión de luz de capas de nanofósforos (nanocristales de GdVO4:Eu3+). Hemos desarrollado sistemas fotónicos adaptados a cada caso y hemos hecho una caracterización óptica y electrónica de todos los dispositivos. La nanoestructuración en forma de cristal fotónico bidimensional provee a las capas activas con propiedades de guías de onda resonantes, mejorando sus propiedades de confinamiento de la luz en las longitudes de onda deseadas, demostrando así la posibilidad de implementar las arquitecturas.
Currently, one of the main challenges in light management at the nanoscale is the transition from the laboratory to real applications. Despite the great potential shown by photonic architectures to optically improve the performance of many devices, transitioning into marketable devices is often hampered by the low-throughput and expensive nanofabrication techniques involved. This thesis is devoted to the design and development of subwavelength light managing strategies to improve the light harvesting or out-coupling in solar cells, photodetectors and light emitters while using a scalable nanostructuration such as soft nanoimprint lithography (NIL). This technique has been proven to achieve resolutions down to few tens of nanometers with high fidelity in large areas, being compatible with roll to roll processing. It is also versatile regarding the materials where it can be used, non-invasive, and can be seamlessly introduced in the devices fabrication scheme. With the aid of this technique, we explore a variety of photonic architectures and the different types of resonances sustained, from Brewster modes to Mie resonances, in order to enhance the light-matter interaction with the active layer of the device. First, we develop a strategy to achieve broadband optimal absorption in ultra-thin semiconductor materials (less than 100 nm thick) for all energies above their bandgap. The interplay of strong interference thin film resonances and photonic crystal modes sustained by a high refractive index nanostructure on a gold film renders the system with a 81% total absorption over a broad spectral range (from 400 to 1500 nm). Second, we combine soft NIL and chemical vapor deposition to obtain an array of silicon hemispheres on top of a high refractive index dielectric waveguide. We study the Mie resonances supported by the substrate, how these hybridize with the guided modes of the waveguide and how their interaction influences the electromagnetic near field of the metasurface. We further explore the tunability of such resonances with the design parameters of the structure and we demonstrate a potential application of it as a substrate for enhanced photoluminescence. In the third part of the thesis, we focus on the implementation of 2D photonic structures within the active layer of three different devices to improve performance. In particular we enhance the near infrared (NIR) photon harvesting efficiency in a colloidal quantum dot solar cell (PbS-CQD) and in organic photodetectors (P3HT: PC60BM and PBTTT: PC70BM) and improve the light out coupling from a nanophosphor layer (GdVO4:Eu3+ nanocrystals). We developed photonic systems tailored for each device and provide the complete optical and electronic characterization for each case. The nanostructuration with a 2D periodic arrangement renders the active layers with resonant waveguide properties enhancing its light trapping properties in the targeted spectral ranges, hence demonstrating the possibility to implement photonic schemes within actual devices.
Universitat Autònoma de Barcelona. Programa de Doctorat en Ciència de Materials

Le silicium est reconnu comme étant un mauvais émetteur de lumière à cause de son gap indirect. Diverses stratégies ont été développées pour améliorer son rendement d'émission, le Si constituant le matériau de choix pour la photonique. Ce manuscrit présente l'élaboration et la caractérisation de matériaux originaux à base de silicium afin de proposer des solutions alternatives pour améliorer les propriétés d'émission de lumière du Si. Ce travail est divisé en 4 parties avec tout d'abord une revue de l'état de l'art de l'émission de lumière dans le Si et les bases sur les mécanismes de recombinaison dans le Si. Une seconde partie se concentre sur l'élaboration et l'étude de dispositifs électroluminescents à base de Si comportant un réseau de dislocations enterrées un niveau d'une jonction PN obtenu par collage moléculaire. L'émission de lumière située vers 1,1 et 1,5 µm (1,1 et 0,8 eV) est attribuée à la recombinaison des porteurs sur les états piège induits par des précipités de bore et d'oxyde dans le voisinage de dislocations (E^phonon_Bore vers 1.1eV et Dp~0.8eV) et des états de défauts localisés à l'intersection du réseau carré de dislocations vis (D1~0.8eV). Une troisième partie traite de l'élaboration et des propriétés optique d'ions Er3 + couplés avec des nanostructures de Si dans des films minces de SRO (Silicon-Rich Oxide) obtenus par co-évaporation de SiO et d'Er. Dans cette matrice, l'efficacité d'excitation indirecte de l'Er à 1,5 µm via les nanostructures est démontrée par la mesure de sections efficaces effectives d'excitation de l'Er entre 2x10-16 cm2 et 5x10-15 cm2 en fonction du flux d'excitation et des paramètres d'élaboration. Le principal résultat est la forte diminution avec la température de recuit de la fraction d'ions Er3+ émetteurs susceptible d'être inversée. Des expériences EXAFS révèlent que ce comportement est en corrélation avec l'évolution de l'ordre chimique local autour des atomes d'Er. Dans une dernière partie est présentée l'élaboration de nanostructures de Si de type nanofils cœur-coquille Si/SiO2. Ces structures cœur-coquille sont obtenues par trois méthodes différentes. Les structures obtenues par dépôt d'oxyde sur la surface de nanofils de silicium CVD catalysées avec de l'Au présentent une émission autour de 500 nm efficace à température ambiante due à la recombinaison des porteurs photo-générés au niveau des états de défauts dans la couche d'oxyde et à l'interface Si/SiO2. L'intensité de PL collectée est de plus d'un ordre de grandeur supérieure à celle mesurée sur des films minces de SiO2 similaires déposés sur des substrats de Si. En outre, la passivation des nanofils de Si CVD par un procédé d'oxydation thermique permet de neutraliser les états de surface qui dominent dans de telles structures. La mesure des vitesses de recombinaison de surface semble indiquer que ces nanofils ainsi passivés présentent des propriétés électroniques de volume similaires à celles du Si standard de microélectronique. Enfin, une nouvelle méthode pour l'élaboration in situ de nanofils cœur-coquille Si/SiO2 basée sur l'évaporation d'une source solide SiO avec l'Au et le Cu comme catalyseurs est détaillée. La croissance des fils catalysés par l'Au se produit dans le mode de croissance VLS (Vapor-Liquid-Solid comme en CVD) donnnat des nanofils présentant un cœur de Si cristallin et une coquille amorphe d'oxyde. En revanche, la croissance des nanofils catalysée par le Cu semble se produire préférentiellement à plus basse température en mode VSS (Vapeur-Solide-Solide) expliquant pourquoi ces NFs présentent une forte densité de défauts cristallins dans la cœur de Si contrairement aux fils catalysés Au
Silicon is known as a poor light emitter due to its indirect band gap. Various strategies have been developed to overcome its poor emission efficiency since it is the material of choice for photonics. In this manuscript are detailed the elaboration and characterization of original silicon-based materials in order to propose alternatives solutions to improve Si light emission properties. This work is divided in 4 parts with a first one describing the state of the art of light emission in Si and the basics of recombination mechanisms in Si. A second part focuses on the elaboration and study of electroluminescent devices based on bulk Si with a buried dislocation network at a PN junction obtained by wafer bonding. The light emission near 1.1 and 1.5 µm (1.1 and 0.8 eV) is attributed to the recombination of carriers on trap states induced by boron and oxide precipitates in the vicinity of dislocations (E^phonon_Bore near 1.1eV and Dp~0.8eV) and defects traps at the intersection of the square network of screw dislocations (D1~0.8eV). In a third part is showed the elaboration and the optical properties of Er3+ ions coupled with Si nanostructures in Si-Rich Silicon Oxide (SRO) thin films obtained by co-evaporation of SiO and Er. We demonstrate the efficient indirect excitation of Er at 1.5 µm with high effective cross sections between 2x10-16 cm2 and 5x10-15 cm2 as a function of the excitation flux and the elaboration parameters. The main result is the drastic decrease of the number of Er3+ emitting ions coupled to Si with the annealing temperature. EXAFS experiments revealed that this behavior is correlated with the evolution of the local chemical order around Er atoms. In a last part is presented the elaboration of Si nanostructures based on core-shell Si/SiO2 nanowires. These core-shell structures are obtained by three different methods. Core-shell nanowires obtained by oxide deposition on the surface of CVD Au-catalyzed Si nanowires exhibit an efficient room temperature emission around 500 nm due to the recombination of photo generated carriers in defects states in the oxide layer and at the Si/SiO2 interface. The collected PL intensity is more than one order of magnitude higher than similar SiO2 thin films deposited on Si substrates. Moreover, the passivation of CVD-growth Si nanowires by a thermal oxidation procedure allows neutralizing the surface states which are predominant in such structures. As a result, the measurement of surface recombination velocities seems to indicate that such passivated nanowires present similar volume electronic properties than standard microelectronic bulk Si. Finally, a new method for the elaboration of in situ core-shell Si/SiO2 nanowires based on the evaporation of a solid SiO source with Au and Cu as catalysts is presented. The Au-catalyzed growth occurs in the VLS mode (Vapor-Liquid-Solid like in CVD-growth) leading to the growth of nanowires with a crystalline Si core surrounded by an amorphous oxide shell. But Cu-catalyzed nanowires growth seems to appear preferentially at lower temperatures in the VSS (Vapour-Solid-Solid) mode explaining why these nanowiress exhibit a high density of crystalline defects in the Si core compared to Au-catalyzed wires

La génération de seconde harmonique magnétique (mSHG pour magnetic Second Harmonic Generation) est un phénomène physique très sensible apparaissant grâce aux brisures de symétrie aux niveaux des surfaces et interfaces des structures métalliques magnétiques. Elle constitue donc un outil puissant pour explorer ce type d'interfaces et des nanostructures. Dans ce travail, nous nous intéressons aux couplages et interactions entre la mSHG et les ondes électromagnétiques pouvant se propager en surface des matériaux. Un intérêt spécifique est porté sur l’ excitation de (i) plasmon polaritons de surfaces (SPP) dans des films métalliques en structures multicouches, (ii) d'anomalies de diffraction (dîtes de Wood) dans des nanostructures métalliques périodiques. Pour étudier l'influence de l'excitation linéaire et non-linéaire des SPP sur la mSHG, l'intensité du signal réfléchi par génération de seconde harmonique (SH) et le contraste magnétique lié à ce signal ont été mesurés par la technique de l'effet Kerr magnéto-optique transverse (MOKE) en fonction de l'angle d'incidence. Via l'utilisation de sources lasers femtosecondes émettant dans le proche infrarouge, domaine spectral où les variations de la dispersion des SPP et du coefficient d'amortissement sont significatives, nous avons pu distinguer les différentes contributions linéaires et non-linéaires aux processus d'excitation. Ce travail de thèse a ainsi permis de montrer que l’accord de phase entre la mSHG et les ondes électromagnétiques de surface peuvent contribuer très efficacement à l'augmentation des signaux SH et de contraste magnétique associé
Owing to surface and interface sensitivity, the magnetic Second Harmonic Generation (mSHG) represents a useful tool to probe magnetic interfaces and nanostructures. This work investigates the coupling and interaction of the mSHG with electromagnetic waves propagating along the surface. Two types of surface waves have been studied: (i) surface plasmon polaritons (SPP) at surfaces of metallic thin films and multilayers, and (ii) the diffraction anomaly at the surface of periodically arranged metallic nanostructures. To study influence of linear and nonlinear excitation of surface waves on the mSHG, the reflected second harmonic (SH) intensity and the magnetic SH contrast in the transverse magneto-optical geometry were measured as a function of the angle of incidence. The use of different femtosecond light sources in the near-infrared optical range, where the SPP dispersion and damping exhibit significant variations, made it possible to disentangle linear and nonlinear contributions to the excitation of surface waves. In this thesis, it is proven that phase-matching of the mSHG and surface electromagnetic waves can lead to the enhancement of both the SH yield and the nonlinear magneto-optical signal. These results are important for controlling of the nonlinear magneto-optical response and could impact the development of magnetic storage devices, label-free biosensors and nonlinear magneto-optical switches

The presented study deals with the sol-gel synthesis of nanocrystalline ternary phases of the general formula ZnxTiyOz, their characterization and potential application in photonics. Achieved results brings new fundamental knowledge about the processes leading to the formation of ZnxTiyOz nanocrystals from amorphous xerogels and gives novel information about structural and opto-electrical properties of prepared materials. Two sol-gel approaches based on the cluster process and direct heteronucleation were employed to prepare initial sol. Sols were optionally doped by Eu3+ ions to evaluate the effects of rare earth element to crystallization properties of formed compounds. In the first part of our study crystallization properties and structural evolution of thermally treated xerogels were analyzed. As a result a versatile method allowing the preparation of inverse spinel Zn2TiO4, cubic defect spinel ZnTiO3 and rhombohedral ZnTiO3 with tailored nanocrystal sizes was established. In the second part of the study, approaches elaborated in the first part were successfully exploited for the preparations of thin films with define nanocrystalline structure and selected composition. . Refractive indexes, dispersion curves and band gap energies of particular structures were determined. In the third part of our study the zinc oxide nanoparticles prepared by the solgel process can be successfully employed as a part of host matrixes for rare earth element allowing the preparation of active optical fibers with parameters close to optical fibers prepared by the standard or modified solution doping method
L'étude examine la préparation de phases ternaires de formule générale ZnxTiyOz par la voie sol-gel, leur caractérisation et l'application éventuelle dans la photonique. Résultats obtenus apporte des nouvelles connaissances fondamentales sur les processus de formation de nanocristaux ZnxTiyOz de xérogels amorphe et donne des nouvelles informations sur les propriétés structurales et opto-électrique de matériaux préparés. Sur la base des résultats présentés, la plupart de toutes de phase reportée composant de ZnxTiyOz avec la taille et la structure nanocristalline façonner peuvent être préparés comme des poudres ou des couches minces. Une méthode souple qui permet la préparation de spinelle inverse Zn2TiO4, cubes spinelle défaut ZnTiO3 et rhomboédrique ZnTiO3 avec des tailles de nanocristaux a été créé sur mesure. Dans la deuxième partie de l'étude, les approches élaborées dans la première partie ont été exploitées avec succès pour la préparation des couches minces à définir la structure et la composition nanocristallin sélectionné. Dans la troisième partie on a démontré que des nanoparticules d'oxyde de zinc préparé par le procédé sol-gel peut être utilisé avec succès dans le cadre des matrices d'accueil pour l'élément terre rare permettant la préparation des fibres optiques actives avec des paramètres près de fibres optiques préparé par la solution standard ou par la méthode de dopage modifiée

Ce manuscrit s’intéresse principalement à l'influence de la répulsion entre électrons libres sur la réponse optique des métaux. Les modèles de matériaux classiques considèrent que la réponse d'un métal est locale -- c'est à dire que la réponse en un point dépend exclusivement des champs en ce point. La prise en compte de la répulsion entre électrons conduit à adopter une description dite non locale de la réponse métallique. Cette thèse explore de façon théorique et numérique les effets de la non-localité sur les propriétés optiques de nanostructures métallo-diélectriques dans le visible et le proche infra-rouge. A l'aide d'un modèle hydrodynamique il est montré que, de façon surprenante, les modes d'interstices plasmoniques peuvent être sensible à la non-localité pour des épaisseurs de plusieurs dizaines de nanomètres. Il est également montré que le plasmon de surface lui même peut être sensible à la non-localité à condition de considérer une interface entre le métal et un diélectrique d'indice suffisamment élevé. Nous proposons et étudions (théoriquement) ici plusieurs configurations simples et réalistes (coupleurs à prisme et à réseaux) pour la mise en évidence expérimentale de la non-localité sur des structures dont les échelles caractéristiques sont de l'ordre de plusieurs dizaines ou centaines de nanomètres. Enfin, dans une seconde partie du manuscrit, le formalisme et les considérations numériques nécessaires à l'étude du rayonnement d'un dipôle dans une structure multi-couche sont présentés en détail puis validés grâce à des comparaisons de dyadiques de Green, diagrammes de rayonnement, et taux d'émission avec des cas disponibles dans la littérature
This manuscript is mainly focused on the influence of repulsion between free electrons on the optical response of metals. Classical material models consider that the metallic response is local -- i.e. that the response at a given point only depends on the fields at this point. Taking into account the repulsion between electrons leads to a so-called non-local description of the metalic response. This thesis explores in a theoritical and numerical way the effects of non-locality on the optical properties of metallo-dielectric nanostructures in the visible and near infrared. Using a hydrodynamical model it is shown that, suprisingly, the modes of plasmonic gaps can be sensitive to non-locality for thicknesses of several tens of nanometers. It is also shown that the surface plasmon itself can be sensitive to non-locality provided that an interface between a metal and a sufficiently high refractive index dielectric is considered. We propose and study here several simple and realictic setups (prism and grating couplers) which would allow to experimentally observe the impact of non-locality and which have characteristic scales of tens or even hundreds of nanometers. Finally, in a second part of the manuscript, the formalism and numerical considerations necessary for the study of a dipole radiation in a multi-layered structure are presented in detail and then validated thanks to comparisons of Green dyadics, radiation diagrams, and emission rates with cases avaible in the literature

Les nanostructures périodiques jouent un rôle important dans le domaine des nanotechnologies, en particulier dans le contrôle des photons. Bien qu'il existe de nombreuses techniques d'usage général pour la fabrication et la simulation optique, nous avons développé une technique de fabrication sur mesure et une méthode de simulation optiques pour les structures périodiques pour accélérer le prototypage à l’échelle du laboratoire et la conception optique. Dans la première partie de cette thèse, nous décrivons une technique lithographique nommée « Laser Interference Lithography » (LIL) à faible coût pour la fabrication de nanostructures périodiques. La technique LIL est combinée avec gravure sèche, gravure humide et technique de gravure électrochimique pour réaliser, respectivement, des trous cylindriques, des pyramides inversées et des réseaux taux de pores bi-périodiques à facteur d’aspect élevé sur le substrat à base de silicium. Les modèles unidimensionnels sur des substrats en verre sont également utilisés comme nanofiltres dans la réalisation de la puce de pré-concentration à faible coût. Dans la deuxième partie, nous décrivons d'abord une méthode de calcul électromagnétique rigoureuse Rigorous Coupled-Wave Analysis (RCWA) conçu pour les structures périodiques. Une description détaillée est donnée pour expliquer la méthode numérique. Ensuite, nous combinons la méthode RCWA et une nouvelle approche proposée de la conception des modèles pseudo-désordonnée pour améliorer le piégeage des photons. A titre d'exemple, nous démontrons que, en ajoutant des structures désordonnées à petite échelle sur des arrangements périodiques à grande échelle, la performance quant à l’absorption des couches minces de silicium peut être grandement améliorée
Periodic nanostructures play an important role in the domain of nanotechnology, especially in photon control. While there exist many general purpose techniques for fabrication and optical simulation, we show tailored fabrication and optical simulation methods for periodic structures to accelerate lab-scale prototyping and optical design. In the first part of this dissertation, we describe a low-cost lithographic technique named Laser Interference Lithography (LIL) for fabricating periodic nanostructures. LIL technique is combined with dry-etching, wet-etching and electrochemical etching technique to realize, respectively, cylindrical holes, inverted pyramids and high aspect ratio pore arrays on silicon based substrate. The one-dimensional patterns on glass substrates are also used as nanofilters in realizing low-cost preconcentration chip. In the second part, we first describe Rigorous Coupled-Wave Analysis (RCWA), a rigorous electromagnetic calculation method designed for periodic structures. A detailed derivation is given to explain the numerical method. Then, we combine the RCWA method and a new proposed pseudo-disordered patterns design approach to investigate photon control. As an example, we demonstrate that by adding ‘appropriate’ engineered fine stripes to each long period the absorption performance of thin silicon slab can be largely enhanced

Reducing the absorber thickness is an attractive solution to decrease the production cost of solar cells. Furthermore, it allows to reduce the amount of material needed and improve the current collection in the cell. This thesis has been focused on the design of nanostructures to enhance light absorption in very small semiconductor volumes in order to achieve efficient ultra-thin solar cells. First, we have proposed an original light-trapping concept for ultra-thin amorphous silicon (a-Si:H) solar cells. A one-dimensional metallic grating is patterned on the front surface of the cell deposited on a metallic mirror. Broadband multi-resonant absorption has been demonstrated for both light polarizations. The metallic grating is also used as an alternative transparent electrode in order to reduce optical losses in the front contact. A detailed analysis of the multi-resonant absorption mechanism has been carried out through numerical calculations. The fabrication and optical characterization of ultra-thin a-Si:H solar cells with metallic gratings have validated the multi-resonant approach.Second, we have proposed a design with a two-dimensional metallic grid as a resonant front contact for very thin (25 nm) gallium arsenide (GaAs) layers. We have shown through the design and fabrication of a proof-of-concept structure the potential of metallic nanogrids to confine efficiently light absorption with an ultra-thin GaAs layer.Finally, advanced light-trapping structures could also allow a thickness reduction of crystalline silicon wafers of a factor 20 to 100 with respect to state-of-the-art cells. We have developed a process to transfer micron-thick epitaxial crystalline silicon (c-Si) layers onto a low-cost host substrate. Inverted nanopyramids have also been fabricated in crystalline silicon in order to achieve a broadband anti-reflection effect. It opens promising perspectives towards the realization of double-sided nanopatterned ultra-thin c-Si cells.

Les travaux de thèse présentés en ce mémoire ont comme objectif principal le développement des sources lasers à semi- conducteurs en cavité verticale sur substrat InP, intègrent des régions actives à nanostructure quantiques, et émettent à des longueurs d’onde “télécom” (1550-1600 nm). Le développement d’un nouveau procédé technologique pour la réalisation de composants VCSEL compactes est détaillé. Ce procédé (nommé TSHEC) a été utilisé pour réaliser des émetteurs VCSELs en pompage optique sur plateforme hôte Si, ayant des performances très satisfaisantes. Ce même procédé a été adapté à la réalisation de VCSELs en pompage électrique, avec une étude préliminaire de la section de confinement électrique basée sur une BTJ en InGaAs, et le développement d’un nouveau jeu de masque dédié. Grace à la mise au point de la technologie des μ-cellules à cristaux liquides réalisé en partenariat avec LAAS, IMT Atlantique et C2N, on a pu adapter le procédé TSHEC pour la réalisation de dispositifs accordables. Une photodiode accordable autour de 1.55 μm a été réalisée, et des émetteurs VCSELs accordables basés sur la même technologie sont actuellement en cours de développement. Dans ces travaux on a également abordé le développement des VECSELs à base de bâtonnets quantiques InAs et émettent à 1.6 μm. Un premier dispositif a été réalisé et caractérisé en régime multimode et mono-fréquence. Finalement, la réalisation d’un banc expérimental pour la mesure directe de la constante de couplage dans des VECSELs bi-fréquence a été détaillée. Ce banc a permis de quantifier précisément le couplage existant entre deux états propres orthogonaux d’un VECSEL à puits quantiques émettent à 1.54 μm, et prochainement permettra la même étude dans des structures anisotropes, tels quels les bâtonnets quantiques ou le boites quantiques, dans le but d’investiguer l’effet de l’élargissement inhomogène présenté par ces milieux à gain en termes de couplage entre modes propres
The work presented in this dissertation focus on the development of InP-based semiconductor vertical-cavity lasers, based on quantum nanostructures and emitting at the telecom wavelengths (1550-1600 nm). A new technological process for the realization of compact VCSELs is described. This process (named TSHEC) has been employed to realize optically-pumped VCSELs, integrated onto a host Silicon platform, with good performances. The same process has been adapted to develop an electrically-driven version of VCSELs: a preliminary study of the confinement section based on a InGaAs-BTJ is presented, together with the development of a mask set. Thanks to the development of the liquid crystals μ-cell technology (in collaboration with LAAS, IMT Atlantique et C2N), we realized a tunable photodiode at 1.55 μm, and a tunable VCSEL is currently under development. This work also presents the first realization of a 1.6 μm- emitting optically-pumped quantum dashes-based VECSELs, and its characterization in multi-mode and single-frequency regime. Finally, the realization of an experimental setup for the investigation of the coupling between two orthogonal eigenstates of a bi- frequency 1.54 μm-emitting SQW-VECSEL has been conceived and realized. This setup, which allowed the direct quantification of the coupling constant on such a device, in the near future will allow performing the same study on anisotropic structures like quantum dashes or quantum dots, with the objective of studying the inhomogeneous broadening effect observed in these gain regions

This thesis presents experimental work on developing rare-earth ions and Si nanostructures as a material platform for light emitting devices (LEDs) in the visible and near-infrared range. The realization of the different electroluminescent devices, based on a single, bi- or tri-layer approach of silicon oxide and/or silicon nitride co-doped or not with rare earth ions, is successfully performed. Several complementary metal-oxide-semiconductor (CMOS) compatible fabrication techniques such as co-magnetron sputtering, plasma-enhanced chemical vapor deposition (PECVD), low-pressure chemical vapor deposition (LPCVD) and ion implantation are used. By using characterization techniques such as time of flight secondary ion mass spectrometry (TOF-SIMS), secondary ion mass spectrometry (SIMS), X-ray photoelectron spectroscopy (XPS), energy-filtered transmission electron microscopy (EFTEM), focused ion beam (FIB) and ellipsometry, the structural and compositional properties of the studied active layers are determined. In addition, electro-optical properties at room and at high temperatures (25 0C – 300 0C) under quasi-static and dynamic regimes are studied in both visible and near-infrared spectral region. Typically, the used electro-optical techniques have been current-voltage, capacitance-voltage, charge to breakdown, electroluminescence (EL)-current, EL-voltage and time-resolved EL.
Esta tesis presenta un trabajo experimental en el desarrollo de iones de tierras raras y nanoestructuras de Si como plataforma de materiales para dispositivos de emisión de luz (LEDs) en el rango visible e infrarrojo cercano. Se han fabricado diferentes dispositivos electroluminiscentes basados en capas simples, dobles o triples de óxido de silicio y/o nitruro de silicio dopados o no con tierras raras. Para ello se han empleado varias técnicas de fabricación compatibles con la tecnología CMOS; a saber, depósito de vapor químico asistido por plasma (PECVD), pulverización catódica mediante magnetrón, depósito de vapor químico a baja presión (LPCVD) e implantación de iones. Así mismo, las propiedades estructurales y de composición de las capas fabricadas han sido determinadas mediante el uso de técnicas de caracterización tales como TOF-SIMS, SIMS, XPS, EFTEM, FIB y elipsometría. Además, a temperatura ambiente y altas temperaturas (25 0C – 300 0C) se han estudiado las propiedades electro-ópticas en los regímenes cuasi-estático y dinámico. Por lo general, las técnicas electro-ópticas empleadas fueron corriente-voltaje, capacitancia-voltaje, estudio de carga hasta la ruptura, electroluminiscencia (EL)-corriente, EL-voltaje y EL resuelta en tiempo.

Esta tesis describe el diseño, la fabricación y la caracterización óptica de sistemas plasmónicos resonantes capaces de confinar y aumentar campos de luz en la escala manométrica. En primer lugar, se utilizaron modelos numéricos 3D para diseñar diferentes geometras de nanoestructuras plasmónicas acopladas, a través del cálculo de la respuesta óptica de su campo lejano y cercano. Sobre la base de estas simulaciones se fabricaron las nanoestructuras por litografía de haz electrónico. Se puso especial énfasis en el aumento de la resolución y la optimización de la reproducibilidad de parámetros críticos como la forma de las partículas y el gap entre ellas. Por último, se empleó espectroscopía de campo lejano combinada con espectroscopía de luminiscencia inducida por dos fotones (TPL) para sondar la respuesta óptica local de las geometrías optimizadas. Hemos centrado nuestra atención en diferentes tipos de estructuras metálicas: dímeros, antenas con gap, conjuntos finitos de partículas en cadenas y en forma de estrella. Los dímeros tienen una fuerte amplificación del campo en su gap nanométrico por el acoplamiento en campo cercano de sus resonancias plasmonicas dipolares. Análogamente, antenas con gap, formadas por dos barras de oro adyacentes que soportan resonancias multipolares, pueden acoplar de manera eficiente la luz y concentrarla en volúmenes pequeños. Se ha demostrado que cadenas finitas de partículas son buenos candidatos para guiar la luz a través de secciones transversales por debajo de la longitud de onda y aquí demostramos que también se pueden utilizar como nanolentes capaces de concentrar la luz en su extremo. La distribución del campo cercano en conjuntos de partículas de oro en forma de estrella presenta una fuerte dependencia con la polarización del campo incidente que puede ser explotada para dirigirse dinámicamente a nano-objetos. La espectroscopía de campo lejano de conjuntos de dímeros y de cadenas finitas de partculas se comparó con la espectroscopía de TPL. Nuestro principal resultado es mostrar que la TPL es preferentemente sensible a los campos locales, permitiendo evaluar características espectrosc ópicas que no podrían resolverse de otro modo. A fin de superar las limitaciones de las medidas de conjuntos, en una segunda etapa se dedicó un considerable esfuerzo a construir y optimizar un montaje óptico para medir la señal de TPL de estructuras únicas. El uso de la micro-espectroscopía de TPL permitió obtener mapas espectrales de los modos de antenas aisladas con resolución espacial. Como se predijo mediante cálculos, hemos sido capaces de visualizar directamente, en la resonancia, la señal de TPL amplificada dentro del gap. Nuestros resultados muestran cómo las medidas de TPL pueden compararse directamente con la distribución de la cuarta potencia del campo local calculado. Mediante el análisis de la evolución de la señal de TPL en función de la longitud de onda incidente en el gap y en las extremidades de la antena tenemos más conocimiento sobre el mecanismo físico detrás de la resonancia de la antena. Finalmente, la microscopía de TPL se utilizó para sondar el campo cercano para diferentes orientaciones de la polarización lineal incidente sobre los conjuntos de partículas en forma de estrella. Se demuestra que, a diferencia del espectro de dispersión, la distribución de TPL en la estructura depende drásticamente del estado de polarización incidente. Nuestro estudio aporta una contribución significativa al campo de la óptica de plasmones, proponiendo nuevas geometrías para confinar de manera eficiente los campos ópticos a la escala nanometrica, aportando un profundo conocimiento sobre el uso de micro-espectroscopa de TPL como sonda óptica local. Nuestros resultados tendrán importancia en aplicaciones tales como espectroscopía mejorada, biosensores y la interacción luz-materia, donde se necesita evaluar el campo experimentado por una pequeña cantidad de materia cercana a la nanoestructura.
This thesis describes the design, fabrication and the optical characterization of plasmon-resonant systems able to confine and enhance light fields down to the sub-wavelength scale. Extensive 3D numerical modeling was first used to design different geometries of coupled plasmonic nanostructures through the calculation of their far-field and near-field optical response. On the basis of simulations, the nanostructures were fabricated by e-beam lithography and thin film deposition. Special efforts were devoted to increasing the resolution and optimizing the reproducibility of critical parameters such as particle shape and interparticle gaps. Finally, far-field spectroscopy combined with two-photon induced luminescence (TPL) spectroscopy was used to probe the local optical response of the optimized architectures. We focused our attention on different families of structures: metal dimers, bar antennas, finite chains of nanoparticles and star-like particle arrangements. Particle dimers feature strong field enhancements in their sub-wavelength gap due to near-field coupling of their dipolar localized plasmon resonances. Based on the same physics, gap antennas, formed by two adjacent gold bars supporting multipolar resonances can efficiently couple to propagating light and concentrate it into tiny volumes. While finite particle chains were previously shown by other authors to be good candidates to guide light through subwavelength cross-sections, we show here that they can also be used as efficient nanolenses able to concentrate light at their extremity. Finally, the near-field distribution in star-like arrangements of gold nanoparticles exhibits a strong dependence with the incident field polarization which can be exploited for dynamical optical addressing of nano-objects. We have compared the far field spectroscopy of large ensembles of dimers and finite chains to TPL spectroscopy. Our main result is to show that TPL is preferentially sensitive to local fields and that it enables the assessment of spectroscopic features which cannot be resolved otherwise. In order to overcome the limitations of measurements on large ensembles a considerable effort was dedicated to mounting and optimizing an optical set-up enabling TPL measurement of single structures. Using the developed TPL micro-spectroscopy, spatially resolved spectral mode mapping on single resonant gap-antennas was achieved. As predicted by calculations, we were able to directly visualize at resonance the strongly enhanced TPL signal within the gap. Our results show how TPL scans can be directly compared with the convoluted distribution of the fourth power of the calculated local mode field. By monitoring the evolution with the incident wavelength of the TPL signal within the gap and at the antenna extremities we got further insight in the physical mechanism behind the buildup of the antenna’s resonance. Finally, TPL microscopy was used to probe the local fields under different orientations of the incident linear polarization near star-like arrangement of gold disks. It is shown that, unlike the scattering spectrum, the TPL distribution over the structure is found to depend drastically on the incident polarization state. Our study brings a significant contribution to the field of Plasmon optics by proposing novel geometries able to efficiently confine optical fields down to the nanometric scale, but also by providing deep insight into the use of TPL microspectroscopy to probe their local optical response. Our findings are foreseen to be important in applications such as enhanced spectroscopy, bio-sensing and enhanced light-matter interaction, where one needs to assess the actual field experienced by small amounts of matter.

Semiconductors provide an interesting platform for studying light-matter interactions due to their unique electrically conductive behavior which can be deliberately altered in useful ways with the controlled introduction of confinement and doping, which changes the electronic band structure. This area of research has led to many important fundamental scientific discoveries that have in turn spawned a plethora of applications in areas such as photonics, microscopy, single-photon sources, and metamaterials. Silicon is the prevalent semiconductor platform for microelectronics because of its cost and electrical properties, while III-V materials are optimal for optoelectronics because of the ability to engineer a direct bandgap and create versatile heterojunctions by growing binary, ternary, or quaternary compounds.

La généralisation des communications numériques (téléphonie mobile, courrier électronique, commerce électronique...) rend nécessaire la mise au point de systèmes dont la confidentialité des informations est garantie de manière absolue. L'utilisation des lois de la mécanique quantique comme moyen de cryptage répond à ce critère. Bien que les physiciens théoriciens aient commencé à réfléchir sur ce type de cryptage depuis les années 1970, les dispositifs effectivement utilisables et industrialisables à grande échelle ne sont pas encore disponibles. Parmi les dispositifs qu'il convient de développer et maîtriser, les sources de lumières capables de générer des photons à l'unité tiennent une place centrale. Une des principales difficultés rencontrées dans leur mise au point réside dans la nécessité d'atteindre une efficacité de collection de la lumière émise proche de l'unité. La solution généralement proposée consiste à maitriser leur environnement électromagnétique à l'aide de résonateurs optiques miniaturisés à l'échelle de la longueur d'onde. On peut ainsi bénéficier d'effets d'électrodynamique quantique, tel que l'effet Purcell, pour améliorer, par exemple, la dynamique et/ou la directivité d'émission des photons. La réalisation pratique de sources de photons n'a été rendue possible que par les progrès des nanotechnologies. L'utilisation de la technologie des semi-conducteurs est la voie prometteuse choisie dans ce travail, dans l'objectif de développer des composants miniaturisés et facilement intégrables, à la base d'une nouvelle génération de résonateurs optiques de taille ultime. Dans ce travail de thèse, nous proposons de développer une source de photons uniques utilisant des boites quantiques InAs -comme émetteurs uniques- incluses dans une membrane GaAs dans laquelle on réalise un résonateur optique consistant en une cavité à cristal photonique membranaire. On exploite la technologie des cristaux photoniques afin d'utiliser un unique mode optique résonant, dit mode de Bloch lent non dégénéré, opérant au-dessus de la ligne de lumière. On exploite diverses méthodes numériques pour la conception et la simulation du comportement électromagnétique des dispositifs. Nous effectuons ainsi une ingénierie fine de modes optiques permettant : (1) d'optimiser le facteur de Purcell dans une hétérostructure photonique(puits photonique analogue des puits quantiques électroniques). Nous montrons que le report de cette cavité sur un miroir de Bragg entraîne le doublement du taux de collection des photons, ainsi que de la dynamique d'émission; (2) de contrôler la directivité d'émission du mode pour améliorer l'efficacité d'extraction /collection des photons. Une étude détaillée de l'ingénierie du diagramme de rayonnement est présentée permettant d'appréhender la physique et de prévoir les caractéristiques10de l'émission du mode. Nous montrons, notamment, que la présence du miroir de Bragg peut fortement modifier la directivité d'émission. Les développements technologiques effectués en vue d'obtenir des résonateurs photoniques de hautes qualités sont également exposés. A la longueur d'onde d'émission de 900nm, choisie pour une adaptation optimale aux caractéristiques des détecteurs, la période du cristal photonique nécessaire est de l'ordre de quelques centaines de nm. Les outils et les paramètres de technologie de fabrication (par exemple, calibration de l'épaisseur du masque dur et des paramètres d'exposition de la résine par lithographie électronique) sont exposés en détail.

This work explores the preparation, characteristics and properties of highly bismuth (Bi) substituted, metal doped, iron garnet compounds and investigates their potential for various emerging applications in the visible and near infrared spectral regions. Bi-substituted iron garnet and garnet-oxide nanocomposite films of generic composition type (Bi, Dy/Lu)3(Fe, Ga/Al)5O12 are prepared by using a radio frequency (RF) magnetron sputtering technique. The physical properties (crystallinity, film morphology, optical absorption spectra across the visible spectral range and the elemental composition of layers), and magneto-optic behaviour (Faraday rotation, hysteresis loops of Faraday rotation, and magnetic switching behaviour) of these sputtered garnet films are investigated in this work. These garnet materials possess high quality nanocrystalline thin-film microstructures and demonstrate excellent combination of optical and magneto-optical (MO) properties which makes them very attractive for use in magneto-optical applications. Record-high MO performance, in terms of the material’s MO figures of merit achieved (which exceeded most or all of the values reported previously for any semi-transparent MO materials across most of the visible spectrum), is achieved simultaneously with high Faraday rotation, making them suitable for a wide range of applications in integrated optics and photonics. The effects of annealing on the garnets of type (Bi,Dy)3(Fe,Ga)5O12, when performed in air atmosphere, are investigated and a systematic study is conducted to figure out the annealing behaviour and the crystallization kinetics of garnet formation within the garnet-bismuth oxide nanocomposites. Also, several nano-engineered magnetooptically active heterostructures (all-garnet multilayer-type thin film structures) based on magnetic layers with dissimilar uniaxial (Ku > 0) and in-plane (Ku < 0) magnetic anisotropies are prepared with the purpose of achieving the customised magnetic behaviour and properties (not attainable in single garnet layers) which are very attractive for the development of MO sensing devices and ultra-fast switches.

A recent International Technology Roadmap for Semiconductors (ITRS) report (2.0, 2015 edition) has shown that Moore’s law is unlikely to hold beyond 2028. There is a need for alternate devices to replace CMOS based devices, if further miniaturization and high energy efficiency is desired. The goal of this dissertation is to experimentally demonstrate the feasibility of nanomagnetic memory and logic devices that can be clocked with acoustic waves in an extremely energy efficient manner. While clocking nanomagnetic logic by stressing the magnetostrictive layer of a multiferroic logic element with with an electric field applied across the piezoelectric layer is known to be an extremely energy-efficient clocking scheme, stressing every nanomagnet separately requires individual contacts to each one of them that would necessitate cumbersome lithography. On the other hand, if all nanomagnets are stressed simultaneously with a global voltage, it will eliminate the need for individual contacts, but such a global clock makes the architecture non-pipelined (the next input bit cannot be written till the previous bit has completely propagated through the chain) and therefore, unacceptably slow and error prone. Use of global acoustic wave, that has in-built granularity, would offer the best of both worlds. As the crest and the trough propagate in space with a velocity, nanomagnets that find themselves at a crest are stressed in tension while those in the trough are compressed. All other magnets are relaxed (no stress). Thus, all magnets are not stressed simultaneously but are clocked in a sequentially manner, even though the clocking agent is global. Finally, the acoustic wave energy is distributed over billions of nanomagnets it clocks, which results in an extremely small energy cost per bit per nanomagnet. In summary, acoustic clocking of nanomagnets can lead to extremely energy efficient nanomagnetic computing devices while also eliminating the need for complex lithography. The dissertation work focuses on the following two topics: Acoustic Waves, generated by IDTs fabricated on a piezoelectric lithium niobate substrate, can be utilized to manipulate the magnetization states in elliptical Co nanomagnets. The magnetization switches from its initial single-domain state to a vortex state after SAW stress cycles propagate through the nanomagnets. The vortex states are stable and the magnetization remains in this state until it is ‘reset’ by an external magnetic field. 2. Acoustic Waves can also be utilized to induce 1800 magnetization switching in dipole coupled elliptical Co nanomagnets. The magnetization switches from its initial single-domain ‘up’ state to a single-domain ‘down’ state after SAW tensile/compressive stress cycles propagate through the nanomagnets. The switched state is stable and non-volatile. These results show the effective implementation of a Boolean NOT gate. Ultimately, the advantage of this technology is that it could also perform higher order information processing (not discussed here) while consuming extremely low power. Finally, while we have demonstrated acoustically clocked nanomagnetic memory and logic schemes with Co nanomagnets, materials with higher magnetostriction (such as FeGa) may ultimately improve the switching reliability of such devices. With this in mind we prepared and studied FeGa films using a ferromagnetic resonance (FMR) technique to extract properties of importance to magnetization dynamics in such materials that could have higher magneto elastic coupling than either Co or Ni.

Semiconductor nanostructures have attracted considerable research interest due to their unique physical and chemical properties at nanoscale which open new frontiers for applications in electronics and sensing. Zinc oxide nanostructures with a wide range of applications, especially in optoelectronic devices and bio sensing, have been the focus of research over the past few decades. However ZnO nanostructures have failed to penetrate the market as they were expected to, a few years ago. The two main reasons widely recognized as bottleneck for ZnO nanostructures are (1) Synthesis technique which is fast, economical, and environmentally benign which would allow the growth on arbitrary substrates and (2) Difficulty in producing stable p-type doping. The main objective of this research work is to address these two bottlenecks and find a solution that is inexpensive, environmentally benign and CMOS compatible. To achieve this, we developed a Sonochemical method to synthesize 1D ZnO Nanorods, core-shell nanorods, 2D nanowalls and nanoflakes on arbitrary substrates which is a rapid, inexpensive, CMOS compatible and environmentally benign method and allows us to grow ZnO nanostructures on any arbitrary substrate at ambient conditions while most other popular methods used are either very slow or involve extreme conditions such as high temperatures and low pressure. A stable, reproducible p-type doping in ZnO is one of the most sought out application in the field of optoelectronics. Here in this project, we doped ZnO nanostructures using sonochemical method to achieve a stable and reproducible doping in ZnO. We have fabricated a homogeneous ZnO radial p-n junction by growing a p-type shell around an n-type core in a controlled way using the sonochemical synthesis method to realize ZnO homogeneous core-shell radial p-n junction for UV detection. ZnO has a wide range of applications from sensing to energy harvesting. In this work, we demonstrate the successful fabrication of an electrochemical immunosensor using ZnO nanoflakes to detect Cortisol and compare their performance with that of ZnO nanorods. We have explored the use of ZnO nanorods in energy harvesting in the form of Dye Sensitized Solar Cells (DSSC) and Perovskite Solar Cells.

This research used a focused ion beam in order to fabricate record small nano-magnetic structures, investigate the properties of magnetic materials in the rarely studied range of nanometer size, and exploit their extraordinary characteristics in medicine and nano-electronics. This study consists of two parts: (i) Fabrication and study of record small magnetic tunnel junctions (ii) Introduction of a novel method for detection of magnetoelectric nanoparticles (MENs) in the tissue. A key challenge in further scaling of CMOS devices is being able to perform non-volatile logic with near zero power consumption. Sub-10-nm nanomagnetic spin transfer torque (STT) magnetic tunneling junctions (MTJs) have the potential for a universal memory that can address this key challenge. The main problem is to decrease the switching current density. This research studied these structures in sub-10-nm size range. In this range, spin related excitations consume considerably smaller amounts of energy as compared to the larger scale. This research concluded that as predicted a decrease in switching current superior to that of the linear scaling will happen in this size range. Magneto-electric nanoparticles (MENs) can be used to directly couple intrinsic electric-field-driven processes with external magnetic fields for controlling neural activity deep in the brain. These particles have been proven to be capable of inducing deep brain stimulation non-invasively. Furthermore, these magneto-electric nano-particles can be used for targeted drug delivery and are contenders to replace conventional chemotherapy. The circulatory system can deliver a drug to almost every cell in the body; however, delivering the drug specifically into the tumor cell and then releasing it on demand remains a formidable task. Nanomedicine can accomplish this, but ensuring that the drug is released at an appropriate rate once at the target site is an important task. In order to have a complete understanding of the behavior of these MENs when injected into the body, a comprehensive bio-distribution study was performed. This study introduced a novel spectroscopy method for tracing the nanoparticles in the bloodstream. This study investigated the post injection distribution of the MENs in vital organs throughout a period of two months.

Ce travail est consacré à l'épitaxie en phase gazeuse d'organométallique de nanostructures de nitrures en forme de fil et de pyramide, pour lesquelles nous cherchons à comprendre les mécanismes de croissance mis en jeu. Une étude paramétrique complète est présentée pour optimiser et mieux appréhender la croissance de nanofils GaN auto-assemblés non-catalysés. Nous démontrons notamment que l'injection de silane est un paramètre-clé pour la croissance des nanofils grâce à la formation d'une couche SiNx de passivation sur les facettes latérales qui joue le rôle d'un masque favorisant ainsi la croissance verticale. Un nouveau procédé de croissance de nanofils sans silane est aussi proposé dans ce travail en utilisant de très faibles flux de précurseurs qui favorise la formation de facettes verticales. De tels nanofils présentent d'excellentes propriétés structurales et optiques grâce à l'absence de silicium. Par ailleurs, nous montrons que la polarité joue un rôle crucial sur la croissance des nanostructures de GaN puisque la forme des nanostructures peut être simplement déterminée par l'orientation de la polarité: une polarité N résulte en fils alors qu'une polarité Ga en pyramides. Par conséquent, la forme fil/pyramide des nanostructures peut être directement choisie en contrôlant la polarité sur des substrats de saphir ou de GaN. Nous avons justement exploité cette méthode pour obtenir des réseaux ordonnés de fils et de pyramides de GaN en utilisant la croissance sélective à travers un masque nanostructuré par lithographie. De telles nanostructures ont été utilisées pour la croissance d'hétérostructures InGaN/GaN pour obtenir soit des puits quantiques non-polaires sur les flans des nanofils, soit des boîtes quantiques d'InGaN aux sommets des pyramides
This work reports the metal-organic vapour phase epitaxy of III-Nitride wire- or pyramid-shaped nanostructures and focuses on the growth mechanisms related to these two types of GaN nanostrcutures. A complete parametric study is presented in order to optimize and to understand the catalyst-free self-assembled GaN nanowire growths. We demonstrate that the silane flux injection is a key-parameter for nanowire growth thanks to the formation of SiNx passivation layer along the sidewall facets that acts as a mask favoring the vertical growth. A novel silane-free nanowire growth is also proposed in this work using ultra-low precursor flux that favors the formation of vertical facets. Such nanowires exhibit excellent structural and optical properties due to the absence of silicon. In addition, the polarity is found to play a key-role for GaN nanostructure growth, since the nanostructure shape can be basically determined by the polarity orientation: N-polar nanostructure results in wire, whereas Ga-polar in pyramid. Consequently, the shape wire/pyramid of nanostructure can be chosen depending on the polarity control on sapphire or GaN substrates. This method is applied to get ordered arrays of GaN wires and pyramids using selective area growth on patterned mask. Such nanostructures can be used as template for InGaN/GaN heterostructure growth to get either non-polar multi-quantum wells along the wire sidewalls or InGaN quantum dots at the pyramid apex

Ce travail de thèse porte sur les propriétés structurales, optiques et électriques de nanostructures et alliages à base de GaP pour la photonique intégrée sur silicium. Parmi les méthodes d’intégration des semi-conducteurs III-V sur Si, l’intérêt de l’approche GaP/Si est tout d’abord discuté. Une étude de la croissance et du dopage de l’AlGaP est présentée afin d’assurer le confinement optique et l’injection électrique dans les structures lasers GaP. Les difficultés d’activation des dopants n sont mises en évidence. Ensuite, les propriétés de photoluminescence des boites quantiques InGaAs/GaP sont étudiées en fonction de la température et de la densité d’excitation. Les transitions optiques mises en jeu sont identifiées comme étant des transitions indirectes de type-I avec les électrons dans les niveaux Xxy et les trous dans les niveaux HH des boites quantiques InGaAs et de type-II avec les électrons dans les niveaux Xz du GaP contraint. Malgré une modification notable de la structure électronique de ces émetteurs, une transition optique directe et type I n’est pas obtenue ce qui reste le verrou majeur pour la promotion d’émetteurs GaP sur Si. La maitrise de l’interface GaP/Si et de l’injection électrique est par ailleurs validée par la démonstration de l’électroluminescence à température ambiante d’une LED GaPN sur Si. Si l’effet laser n’est pas obtenu dans les structures lasers rubans GaP, un possible début de remplissage de la bande Гdans les QDs est discuté. Enfin, l’adéquation des lasers à l’état de l’art avec les critères d’interconnections optiques sur puce est discutée
This PhD work focuses on the structural, optical, electrical properties of GaP-based nanostructures and alloys for integrated photonics on silicon. Amongst the integration approaches of III-V on Si, the interest of GaP/Si is firstly discussed. A study of the growth and the doping of AlGaP used as laser cladding layers (optical confinement and electrical injection) is presented. The activation complexity of n-dopants is highlighted. Then, the photoluminescence properties of InGaAs/GaP quantum dots are investigated as a function of temperature and optical density. The origin of the optical transitions involved are identified as (i) indirect type-I transition between electrons in Xxy states and holes in HH states of quantum dots InGaAs and (ii) indirect type-II with electrons in Xz states of strained GaP. Despite an effective modification in the electronic structure of these emitters, a direct type I optical transition is not demonstrated. This is the major bottleneck in the promotion of GaP based emitters on Si. This said, the control of the GaP/Si interface and electrical injection are confirmed by the demonstration of electroluminescence at room temperature on Si. If no laser effect is obtained in rib laser architectures, a possible beginning of Г band filling in QDs is discussed. Finally, the adequacy of state of the art integrated lasers with the development of on-chip optical interconnects is discussed

This thesis exploits so called “Optical Eigenmodes” (OEi) in the focal plane of an optical system. The concept of OEi is introduced and the OEi operator approach is outlined, for which quadratic measures of the light field are expressed as real eigenvalues of an Hermitian operator. As an example, the latter is employed to locally minimise the width of a focal spot. The limitations of implementing these spots with state of the art spatial beam shaping technique are explored and a selected spot with a by 40 % decreased core width is used to confocally scan an in focus pair of holes, delivering a two-point resolution enhanced by a factor of 1.3. As a second application, OEi are utilised for fullfield imaging. Therefore they are projected onto an object and for each mode a complex coupling coefficient describing the light-sample interaction is determined. The superposition of the OEi weighted with these coefficients delivers an image of the object. Compared to a point-by-point scan of the sample with the same number of probes, i.e. scanning points, the OEi image features higher spatial resolution and localisation of object features, rendering OEi imaging a compressive imaging modality. With respect to a raster scan a compression by a factor four is achieved. Compared to ghost imaging as another fullfield imaging method, 2-3 orders of magnitude less probes are required to obtain similar images. The application of OEi for imaging in transmission as well as for fluorescence and (surface enhanced) Raman spectroscopy is demonstrated. Finally, the applicability of the OEi concept for the coherent control of nanostructures is shown. For this, OEi are generated with respect to elements on a nanostructure, such as nanoantennas or nanopads. The OEi can be superimposed in order to generate an illumination of choice, for example to address one or multiple nanoelements with a defined intensity. It is shown that, compared to addressing such elements just with a focussed beam, the OEi concept reduces illumination crosstalk in addressing individual nanoelements by up to 70 %. Furthermore, a fullfield aberration correction is inherent to experimentally determined OEi, hence enabling addressing of nanoelements through turbid media.

This thesis is concerned with the fabrication methodology of polymeric photonic crystals operating in the visible to near infrared regions and the correlation between the chemical deposition morphologies and the resultant photonic stopband enhancements of photonic crystals. Multiphoton lithography (MPL) is a powerful approach to the fabrication of polymeric 3D micro- and nano-structures with a typical minimum feature size ~ 200 nm. The completely free-form 3D fabrication capability of MPL is very well suited to the formation of tailored photonic crystals (PCs), including structures containing well defined defects. Such structures are of considerable current interest as micro-optical devices for their filtering, stop-band, dispersion, resonator, or waveguiding properties. More specifically, the stop-band characteristics of polymer PCs can be finely controlled via nanoscale changes in rod spacings and the chemical functionalities at the polymer surface can be readily utilized to impart new optical properties. Nanoscale features as small as 65 ± 5 nm have been formed reproducibly by using 520 nm femtosecond pulsed excitation of a 4,4'-bis(di-n-butylamino)biphenyl chromophore to initiate crosslinking in a triacrylate blend. Dosimetry studies of the photoinduced polymerization were performed on chromophores with sizable two-photon absorption cross-sections at 520 and 730 nm. These studies show that sub-diffraction limited line widths are obtained in both cases with the lines written at 520 nm being smaller. Three-dimensional multiphoton lithography at 520 nm has been used to fabricate polymeric woodpile photonic crystal structures that show stop bands in the visible to near-infrared spectral region. 85 ± 4 nm features were formed using swollen gel photoresist by 730 nm excitation MPL. An index matching oil was used to induce chemical swelling of gel resists prior to MPL fabrication. When swollen matrices were subjected to multiphoton excitation, a similar excitation volume is achieved as in normal unswollen resins. However, upon deswelling of the photoresist following development a substantial reduction in feature size was obtained. PCs with high structural fidelity across 100 µm × 100 µm × 32 layers exhibited strong reflectivity (>60% compared to a gold mirror) in the near infrared region. The positions of the stop-bands were tuned by varying the swelling time, the exposure power (which modifies the feature sizes), and the layer spacing between rods. Silver coatings have been applied to PCs with a range of coverage densities and thicknesses using electroless deposition. Sparse coatings resulted in enhanced reflectivity for the stop band located at ~5 µm, suggesting improved interface reflectivity inside the photonic crystal due to the Ag coating. Thick coatings resulted in plasmonic bandgap behavior with broadband reflectivity enhancement and PC lattice related bandedge at 1.75 µm. Conformal titania coatings were grown onto the PCs via a surface sol-gel method. Uniform and smooth titania coatings were achieved, resulting in systematically red-shifted stopbands from their initial positions with increasing thicknesses, corresponding to the increased effective refractive index of the PC. High quality titania shell structures with modest stopbands were obtained after polymer removal. Gold replica structures were obtained by electroless deposition on the silica cell walls of naturally occurring diatoms and the subsequent silica removal. The micron-scaled periodic hole lattice originated from the diatom resulted in surface plasmon interferences when excited by infrared frequencies. The hole patterns were characterized and compared with hexagonal hole arrays fabricated by focused ion beam etching of similarly gold plated substrate. Modeling of the hole arrays concluded that while diatom replicas lack long-ranged periodicity, the local hole to hole spacings were sufficient to generate enhanced transmission of 13% at 4.2 µm. The work presented herein is a step towards the development of PCs with new optical and chemical functionalities. The ability to rapidly prototype polymeric PCs of various lattice parameters using MPL combined with facile coating chemistries to create structures with the desired optical properties offers a powerful means to produce tailored high performance photonic crystal devices.

Aquesta tesi està dedicada a la nanofabricació, la caracterització i les aplicacions d’estructures híbrides plasmòniques-fotòniques. La possibilitat de treballar amb la llum a la nanoescala, controlar les seves propietats, dirigir el seu flux i concentrar el seu camp elèctric en volums nanomètrics, ha portat al desenvolupament d’un nou camp de la ciència: la nanoplasmònica. Aquest camp està en continu creixement i, juntament amb la nanotecnología, està portant al desenvolupament de nous sistemes optoelectrònics. Aquestes investigacions tenen un gran impacte en camps des de la medicina fins a la conversió d’energia. D’aquí es deriva la necessitat d’estudiar noves tècniques de nanofabricació i caracterització més assequibles que permetin la fabricació a gran escala d’estructures nanomètriques. El manuscrit es compon de dos treballs principals dedicats a la utilització de tècniques de nanofabricació híbrides entre bottom-up i top-down. En primer lloc, s’han fabricat a gran escala noves estructures plasmòniques asimètriques. Les seves propietats òptiques depenen de la polarització lineal o circular de la llum i mostren com l’asimetria geomètrica permet obtenir una resposta òptica específica. D’entre totes les estructures estudiades, les matrius de nanobertura, han estat utilitzades per demostrar l’augment de fluorescència degut a l’interacció d’un colorant amb superfícies metàl·liques nanoestructurades. En segon lloc, s’han fabricat matrius d’agregats de nanopartícules d’or a través de tècniques d’auto-acoblament guiades per un nanopatró de PDMS. La possibilitat d’ajustar les ressonàncies plasmòniques al llarg de tot l’espectre visible i infraroig proper ha permès adaptar el sistema per la seva utilització com a sensor de SERS en medis biològics.
Esta tesis está dedicada a la nanofabricación, la caracterización y las aplicaciones de estructuras híbridas plasmónica-fotónica. La posibilidad de trabajar con la luz a la nanoescala, controlar sus propiedades, manejar su flujo y concentrar su campo eléctrico en volúmenes nanométricos, ha llevado al desarrollo de un nuevo campo de la ciencia: la nanoplasmónica. Este campo está en continuo crecimiento y, junto con la nanotecnología, está llevando hacia el desarrollo de nuevos sistemas optoelectrónicos. Estas investigaciones tienen un gran impacto en campos desde la medicina hasta la conversión de energía. De ahí se deriva la necesidad de estudiar nuevas técnicas de nanofabricación y caracterización más asequibles que permitan un fácil escalado de estructuras nanométricas. El manuscrito se compone de dos trabajos principales, ambos dedicados a la utilización de técnicas de nanofabricación híbridas entre bottom-up y top-down. En primer lugar, se han fabricado en gran escala nuevas estructuras plasmónicas asimétricas. Sus propiedades ópticas dependientes de la polarización lineal o circular de la luz han sido estudiadas desvelando cómo la asimetría geométrica permite obtener una diferente respuesta óptica. Entre todas las estructuras estudiadas, matrices de nanoaperturas han sido utilizadas para demonstrar el aumento de fluorescencia debido a la interacción de un colorante con superficies metálicas nanoestructuradas. En segundo lugar, se han fabricado matrices de agregados de nanopartículas de oro a través de técnicas de auto ensamblaje guiadas por un nanopatrón de PDMS. La posibilidad de ajustar las resonancias plasmónicas a lo largo de todo el espectro visible e infrarrojo cercano ha permitido adaptar el sistema para la utilización como sensores de SERS en medios biológicos.
This dissertation is the result of the work carried out in the Nanostructured Materials for Optoelectronics and Energy Harvesting (NANOPTO) research group at the Institute of Materials Science of Barcelona. Part of this work was conducted in collaboration with the Bionanoplasmonic group at the CIC BiomaGUNE in San Sebastian. This work is dedicated to the nanofabrication, characterization, and application of complex plasmonic nanostructures with engineered optical properties. The possibility to play with light at the nanoscale, control its property, mold its flow and concentrate its electric filed in nanometric volumes has led to the arising of a new field of science: nanoplasmonics. This field is constantly growing at a high pace and, along with nanotechnology, is driving the development of next-generation optoelectronic devices. These new research fields have a broad impact from medicine to energy harvesting hence the interest in studying this filed seeking more affordable nanofabrication techniques which will allow the scale-up of plasmonic devices. The manuscript is divided into three sections, which in turn are divided into several chapters. In Section I, we summarize the optical properties of metals highlighting their importance in plasmonics and describing different approaches to fabricate nanostructured devices, namely top-down and bottom-up. A discussion on the main techniques will highlight the strength of unconventional fabrication methods based on soft nanoimprinting. Section II is dedicated to the fabrication, optical characterization and surface-enhanced fluorescence studies with asymmetric plasmonic crystals. The fabrication process combines thermal nanoimprint lithography (top-down) with tilted thermal evaporation (bottom-up) which allow large scale plasmonic system with homogeneous optical properties over a large area. Finally, section III deals with the merger o nanoimprint lithography and nanoparticle self-assembly to achieve long-range homogeneity of nanoparticles supercrystals. In this discussion, we will present a new controlled method to achieve template self-assembly form both gold nanospheres and nanorods. The optical characterization reveals the hybridization between localized plasmon resonances and diffraction modes which allows the tuning of resonances by changing the lattice parameter of the array. The application of supercrystals as Surface-enhanced Raman spectroscopy sensors will be finally explored, studying intra batch and inter batch signal homogeneity unveiling the critical parameters that affect the SERS signal.

In dieser Arbeit untersuchen wir das optische Antwortverhalten von planaren Spektrometern basierend auf ungeordneten Streuzentren, dielektrischen Verbundnanopartikeln mit einer plasmonischer Ummantelung, sowie volldielektrischen magnetooptischen formveränderten Metaoberflächen. Dafür benutzen wir sowohl Mie und Mehrfach-Streutheorie als auch ein unstetiges Galerkin Zeitraumverfahren basierend auf finiten Elementen zur numerischen Berechnung der elektromagnetischen Felder. Wir stellen insbesondere eine theoretische Designstudie vor, um ungeordnete Spektrometer mit hoher spektraler Auflösung zu erhalten. Darüber hinaus geben wir eine alternative Strategie an, um durch Untersuchung der optischen Eigenschaften von Verbundnanopartikeln eine Erhöhung der bevorzugten Rückstreuung zu erreichen. Zum Schluss präsentieren wir eine Erhöhung der Faraday-Rotation bei gleichzeitig hoher Transmission von volldielektrischen magnetooptischen Metaoberflächen, welche aus formangepassten Nanodisks bestehen.
In this thesis, we study the optical response of planar spectrometers based on disorder scatterers, composite dielectric nanoparticles with plasmonic shell, and all-dielectric magneto-optical shape-modified metasurfaces. Therefore, we employ both Mie and multiple scattering theory as well as a discontinuous Galerkin time-domain method based on finite elements for the numerical computation of the electromagnetic fields. Specifically, we present a theoretical design study for obtaining random spectrometers with high spectral resolution. Furthermore, we provide an alternative strategy to achieve preferentially high backscattering by studying the optical properties of composite nanoparticles. Finally, we present enhanced Faraday rotation along with high transmittance in all-dielectric magneto-optical metasurfaces composed of shape-modified nanodisks.

This thesis discusses nonlinear effects, such as modulation instability and solitons in nano-structured waveguides. The nanoscale optical waveguides have extremely small transverse dimensions, which can provide tight confinement of light. Therefore, by changing the waveguide geometry, the waveguide dispersion can be strongly altered. On the other hand, the confinement also enhances the nonlinear dispersion, allowing for nonlinear optical phenomena supported by dispersion of nonlinearity. The new models governing evolution of the amplitudes of components of the optical waves interacting in the waveguides are derived for continuous wave and pulse wave using perturbation expansion method. The new modulation instability condition is found, as we take into account the dispersion of nonlinearity which is enhanced through a strong variation of the modal profile with the wavelength of light in sub-wavelength waveguides. We demonstrate that this dispersion of nonlinearity can lead to the modulation instability in the regime of normal group velocity dispersion through the mechanism independent from higher order dispersions of linear waves for continuous wave. We address that the new mechanism highly associated with dispersion of nonlinearity in sub-wavelength semiconductor waveguide induces the modulation instability in picsecond regime together with the cascaded generation of higher-order sidebands. The impact of the dispersion of nonlinearity on spectral broadening of short pulses in a silicon waveguide also is considered. We study the temporal evolutions of fundamental and one-ring solitary waves with phase dislocation in dielectric-metal-dielectric waveguides with PT-symmetry and numerically analyze the properties of these nonlinear localized modes and, In particular, reveal different scenarios of their instability.

La consommation d’énergie liée aux technologies de l’information augmente trèsrapidement et dans la mesure où la société a besoin d’être toujours plus connectée tout ens’appuyant sur des solutions durables, les technologies actuelles ne suffisent plus. La photoniqueintégrée s’impose dès lors comme une alternative à l’électronique pour réaliser du traitementdu signal économe en énergie. Au cours de cette thèse, j’ai étudié des structures sub-longueurd’onde en semiconducteur, les cristaux photoniques, qui présentent des propriétés non linéairesimpressionnantes. Plus précisément, le confinement fort et la propagation en lumière lente permettentun traitement sur puce de signal ultra-rapide tout optique, soit à partir de mélange àquatre ondes ou d’auto-modulation de phase. L’originalité est l’utilisation de nouveaux matériauxsemi-conducteurs ayant moins d’absorption non linéaires et par porteurs libres, effets qui limitentla pleine exploitation des effets non linéaires dans les structures photoniques en Silicium. Dansma thèse, des semiconducteurs III-V ont été utilisés pour développer des guides et des cavitéscristal photonique de grande qualité qui sont en mesure de supporter des densités de puissanceoptiques extrêmement élevées ainsi que de grands niveaux de puissance moyenne. J’ai amélioré laconductivité thermique des guides d’ondes grâce à l’intégration hétérogène de membranes GaInPavec du dioxyde de silicium. Cette plateforme permettra à terme de démontrer de l’amplificationsensible à la phase dans le régime continu que j’ai déjà démontré dans le régime pulsé en utilisant des membranes suspendues en GaInP. En parallèle, j’ai démontré des cristaux photoniques de grande qualité dans du Gallium phosphure, qui est un matériau très prometteur en raison de lagrande bande interdite et de la très bonne conductivité thermique. Les résultats préliminaires ontpermis la réalisation d’un régime non linéaire intense (mini-peigne de fréquence, compression etfission de soliton ...)
The energy consumption of the whole ICT ecosystem is growing at a fast paceand in a global context of the search for an ever more connected yet sustainable society, a technologicalbreakthrough is desired. Here, integrated nonlinear photonics will help by providingnovel possibilities for energy efficient signal processing. In this PhD thesis, I have been investigatingsub-wavelength semiconductor structures, particularly photonic crystals, which have shownremarkable nonlinear properties. More specifically the strong confinement and slow light propagationenables on-chip ultra-fast all-optical signal processing, either based on four-wave-mixingor self-phase modulation. The main point here is the use of novel semiconductor materials withimproved nonlinear properties with respect to Silicon. In fact, it has now been acknowledgedthat the nonlinear and free-carriers absorption in Silicon integrated photonic structures is anissue hindering the full exploitation of nonlinear effects. In my thesis, wide-gap III-V semiconductorshave been used to develop high quality photonic crystal waveguides and cavities whichare able to sustain extremely high optical power densities as well as large average power levels.I have demonstrated PhC waveguides with much improved thermal conductivity through heterogeneousintegration of GaInP membranes with silicon dioxide. This will allow continuous wave phase-sensitive amplification, which I already demonstrated in the pulsed regime using GaInPself-suspended membranes. In parallel, I have demonstrated high quality PhC in Gallium Phosphide,which is a very promising material because of the large bandgap and the very good thermalconductivity. Preliminar results demonstrate the achievement of extremely large nonlinear regime(mini-comb, soliton compression and fission ...)

Manipulation of light at the nanoscale has the promise to enable numerous technological advances in biomedical sensing, optical communications, nano-mechanics and quantum optics. As photons have vanishingly small interaction cross sections, their interactions have to be mitigated by matters (i.e. quantum emitters, molecules, electrons etc.). Waveguides and cavities are the fundamental building blocks of the optical circuits, which control or confine light to specific matters of interest. The first half of the thesis (Chapters 2 & 3) focuses on how to design various photonic nanostructures to manipulate light on nano- to micro- scale, especially to modify the light-matter interaction properties. Chapter 2 discusses how nano-slot waveguides and photonic crystal nanobeam waveguides are able to modify the emission of quantum emitters, in a different way that normal ridge waveguides are not able to. Chapter 3 focuses on a more complicated and powerful structure: the photonic crystal nanobeam cavity. The design, fabrication and characterization of the photonic crystal nanobeam cavities are described and demonstrated in detail, which lays out the foundation of the biomedical sensing applications in the second half of the thesis. The second half of the thesis (Chapters 4 & 5) focuses on the application of photonic crystal nanobeam cavities in the label-free sensing of biomedical substances. Chapter 4 demonstrates detection of solutions with different refractive index (aceton, methanol, IPA etc.), glucose concentration, single polystyrene nanoparticles and single streptavidin bio-molecules. Chapter 4 proposes a novel nonlinear optical method to further enhance the sensitivity. Chapter 4 also demonstrates high quality nanobeam cavities fabricated in polymers, that open up a new route to decrease the cost, as well as to achieve novel applications with functional polymers. The broader impact of this technology lies in its potential of commercialization of a new generation of biosensors with high sensitivity and high integration. Chapter 5 discusses progresses towards instrumentation of the nanobeam cavity sensing technology for research & development apparatus, as well as point-of-care diagnostic tools.
Engineering and Applied Sciences

Avec les avantages significatifs de stockage, de traitement et de transmission des informations, la science de l’information quantique a attiré des études abondantes lors des dernières décennies, par lesquelles de nombreuses preuves de principe ont été faite en utilisant des techniques expérimentales macro-photoniques. Cependant, l'applicabilité de ces technologies dépend fortement de la miniaturisation du système, i.e. l'intégration « sur-puce » des fonctionnalités photoniques quantiques. Les conditions prérequis générales d'une puce quantique intégrée sont la génération, le transport et la détection localisée et efficace de photons. Des efforts ont été réalisés avec succès comportant une ou deux fonctions nécessaires. Cependant, l'intégration complète reste encore inachevée. Basé sur des éléments nano-photoniques de semiconducteurs et des techniques de nano-fabrication simples, cette thèse vise à fournir une stratégie d'intégration « sur-puce ». Une excitation efficace et locale d'une source de photon unique par un guide d'onde inférieure à l'échelle de la longueur d'onde est d'abord démontrée. Ensuite, nous étudions l’échange efficace de la lumière entre les nanostructures et les guide d'onde, qui peuvent servir le bloc de liaison entre les dispositifs dans un système d'intégration. La fabrication et la caractérisation d'un photo-détecteur sensible basé sur un nanofil unique sont présentées, qui présente un grand potentiel pour la détection de photons uniques. A la fin, une perspective de l'intégration ultime de toutes ces fonctionnalités est fournie
With the significant advantages in storing, processing and transmitting information, quantuminformation science has attracted abundant studies in the last few decades, by which many proofs ofprinciple have been made using macro-photonic experimental techniques. However, the applicabilityof this technology still strongly depends on the miniaturization of the system, i.e. the on-chip integration of quantum photonic functionalities. The general prerequisites of an integrated quantumchip are localised and efficient generation, transportation and detection of photons. Some effortshave been made successfully involving one or two necessary features. However, the full integration still remains unaccomplished. Based on semiconductor nanophotonic elements and simple nanofabrication techniques, this thesis aims to provide a strategy for on-chip quantum photonic integration. An efficient and local excitation of a single photon source with a subwavelengthwaveguide is firstly demonstrated. Then we investigate the efficient light exchange betweennanostructures and waveguides that can serve as linking blocks between devices in an integrationsystem. The fabrication and characterisation of a sensitive photodetector based on a single nanowireis also presented, which exhibits great potential in single-photon detection. At the end, an outlook ofthe ultimate integration of all these functionalities is provided

This thesis presents studies on light management in optoelectronic devices. The broad aim of the thesis is to improve the efficiency of optoelectronic devices by optimised light usage. The studies emphasise the design and fabrication of nanostructures for optimised photon control. A key hypothesis guiding the research is that better designs can be achieved by ab initio identification of their desired Fourier properties. The specific devices studied are organic Distributed Feedback (DFB) lasers, organic solar cells and silicon solar cells. The impact of a substructured grating design capable of affording unprecedented control over the balance between feedback and output coupling in DFB organic lasers was investigated both experimentally and theoretically. It was found experimentally that such gratings can halve the threshold of organic DFB lasers. The reduction in the laser threshold is associated with reduced output coupling and higher feedback provided by the substructured gratings. The possibility of improving the efficiency of organic solar cells by trapping light into the absorbing medium was investigated. It was found that the low refractive index of the organic gain medium compromises the light trapping performance. It was found that strong absorption enhancement, however, can be achieved using plasmonic nanostructures. Finally, a novel design concept for light trapping in silicon solar cells is proposed. This design takes advantage of grating structures with long periods that are capable of providing broad-band light trapping, which is an important requirement for silicon solar cells. The design is based on a supercell that enables better light injection through manipulation of the grating's Fourier properties. The design idea leads to the formation of quasi-random nanostructures that afford great versatility for photon control. Strong light trapping was achieved and characterised both theoretically and experimentally.

A microscopic analysis of a vertical stack of self-assembled InAs/GaAs lens-shaped quantum dot nanostructures is presented. The analysis revolves around a rigorous Hamiltonian formulation of an eight-band k.p. perturbation to account for the lattice-mismatch strain endured by the islands. The numerical implementation yields the effective bandgap energy and electronic structure of an InAs/GaAs quantum dot. Within the framework of a resonant two-level energy system, material gain and absorption spectra are calculated up to a third-order susceptibility to include nonlinearity. The material gain polarization dependence is expressed in the dipole transition strength. Polarization-dependent anisotropy factors corresponding to different interband transitions are derived and shown to satisfy a momentum conservation rule. Modal analysis of a rectangular core waveguide realized by imbedding the active quantum dot layer(s) into a cladding medium with lower refractive index is presented. Polarization-independent modal gain is achieved by optimizing the width of the rectangular core waveguide. In illustration of a quantum dot device, a realistic semiconductor optical amplifier model accounting for both stimulated and spontaneous emission is considered. The calculated carrier density longitudinal profile yields other parameters characterizing the amplifier performance.

L’auto-assemblage de particules colloïdales est une technique polyvalente qui permet la fabrication de cristaux colloïdaux à de grandes échelles. Le but de notre étude est de développer des processus fiables et reproductibles pour fabriquer des matériaux photoniques et plasmoniques pouvant être incorporés au sein de différents dispositifs.Des opales inverses en dioxyde de titane composées d’un nombre précis de couches ont été intégrées au sein de cellules solaires à colorant «tout solide», ce qui a entraîné une amélioration des performances allant jusqu'à105%. Des surfaces d'ornano structurées présentant une absorption omnidirectionnelle et totale de la lumière ont été fabriquées par dépôt électrolytique d'or à travers une monocouche de particules de polystyrène. En outre, des surfaces d'or très rugueuses présentant des propriétés anti-réfléchissantes ont également été élaborées. En modulant la taille des interstices entre les particules de polystyrène, il a été possible de fabriquer par électrodéposition séquentielle des nanopiliers d’or de différentes longueurs. Enfin, l'utilisation d'une monocouche non compacte de particules comme moule a permis la réalisation de métamatériaux de type fishnet
The bottom-up self-assembly of colloidal particles is a versatile technique that allows the fabrication of large areas of colloidal crystals. The purpose of the present study is to develop highly reliable and reproducible process routes to fabricate nanostructured photonic and plasmonic materials that can be incorporated into different devices. Titania inverse opals with precise control of the layer thickness have been successfully incorporated into solid state DSSCs which showed improved performance of up to 105 %. Nanostructured gold surfaces that exhibited omnidirectional total light absorption have been fabricated by controlled electrodeposition of gold through colloidal monolayers of polystyrenebeads. In addition, very rough gold surfaces that showed anti-reflective properties were also made. By tuning the pore size of the colloidal monolayer, plasmonic gold nanopillarswith different lengths were fabricated by a sequential electrodeposition process. Using a non close-packed monolayer of PS beadscombined with electrodeposition,fishnet metamaterialswere fabricated