Semiconducting nanocrystals in open-access microcavities are promising systems in which enhanced light-matter interactions lead to quantum effects such as the modulation of the spontaneous emission process and exciton-polariton formation. In this thesis I present improvements of the open cavity platform which serves to confine the electromagnetic field with mode volumes down to the λ³ regime and demonstrate results in both the weak and strong coupling regimes of cavity quantum electrodynamics with a range of different low-dimensional materials. I report cavity fabrication details allowing a peak finesse of 5 × 10⁴ and advanced photonic structures such as coupled cavities in the open cavity geometry. By incorporating two-dimensional materials and nanoplatelets in the cavity I demonstrate the strong coupling regime of light-matter interaction with the formation of exciton-polaritons, quasi-particles composed of both photon and exciton, at room temperature. In the perturbative weak coupling regime I show pronounced modulation of the single-photon emission from CdSe/ZnS quantum dots and the two-dimensional material WSe₂ and demonstrate Purcell enhancement of the spontaneous emission rate by factors of 2 at room temperature and 8 at low temperature. The findings presented in this thesis pave the way to establish open microcavities as a platform for a wide range of applications in nanophotonics and quantum information technologies.

Orientador: Newton Cesário Frateschi / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-08-24T10:26:52Z (GMT). No. of bitstreams: 1 Barea_LuisAlbertoMijam_D.pdf: 8459370 bytes, checksum: 5dd565986711cb06cb24cf63d6d69372 (MD5) Previous issue date: 2014 / Resumo: Sistemas fotônicos baseados em ressonadores na forma de anéis tem uma dependência fundamental dada pela relação estreita entre espaçamento espectral livre (Free Spectral Range, FSR), fator de qualidade total, Q, e o raio dos ressonadores, R. Nesta tese, nós quebramos esta dependência empregando moléculas fotônicas (Photonic Molecules, PMs) baseadas em múltiplos anéis internamente acoplados a um anel externo, que por sua vez está acoplado a um guia de onda. Aplicando o método de matriz de transferência (Transfer-Matrix Method, TMM) e programas robustos de simulação, nós projetamos três tipos de PMs baseada em uma plataforma de Silício-sobre-isolante (Silicon-on-Insulator, SOI). Este projeto mostrou que o acoplamento entre duas ou mais micro-cavidades ópticas, permite separações espectrais e hibridização dos modos quando as frequências ressonantes estão degeneradas nas cavidades, similar ao acoplamento fraco entre átomos. Estas PMs foram fabricadas com um processo convencional e compatível com a tecnologia CMOS, empregando uma Foundry, e suas caracterizações mostraram a emergência de dupletos, tripletos, quadrupletos e sextupletos de ressonâncias degeneradas, com alto Q e espaçamentos curtos, somente possíveis com anéis de algumas ordens de magnitude maiores em área. Estes resultados quebraram o paradigma da interdependência entre Q, FSR e R, evidenciando que é possível ter tempo de vida fotônico, espaçamento espectral e área independentes. As aplicações destas PMs em processamento de sinal óptico também foram demonstrados neste trabalho. Nós apresentamos o uso da molécula com dupleto de ressonâncias para extrair um sinal RF de 34.2 GHz, filtrando as bandas laterais de um sinal modulado. Também foi demonstrado que moduladores ópticos ultracompactos operando à 2.75 vezes acima do limite da largura de linha do ressonador pode ser obtido a partir da PM que apresenta um tripleto de ressonâncias, separadas de ~55 GHz. Finalmente, utilizando a molécula que permite obter um quadrupleto de ressonâncias, foi demonstrado a conversão de comprimento de onda totalmente óptico (multicasting) para quatro canais convertidos e separados de 40-60 GHz, utilizando apenas 1 mW de potência de controle / Abstract: Photonic systems based on microring resonators have a fundamental constraint given by the strict relationship among free spectral range (FSR), total quality factor (Q) and resonator size (R). In this thesis, we break this dependence employing CMOS compatible photonic molecules (PMs) based on multiple inner ring resonators coupled to an outer ring, which is coupled to a straight bus waveguide. Applying the transfer matrix method (TMM) and simulation robust programs, we project three types of PM based on scalable silicon-on-insulator (SOI) platform. This project shows that the coupling between two or more optical micro-cavities, allows spectral splitting and hybridization of the modes when the resonant frequencies are degenerated in the cavities, similar to weak coupling between atoms. These PMs were fabricated in a conventional CMOS Foundry and your characterization shows the emergence of doublet, triplet, quadruplet and sextuplet of degenerated resonances, with high-Q and close-spaced, only achievable with single-ring orders of magnitude larger in footprint. These results break the paradigm of the interdependence between Q, FSR and R, evidencing that is possible to have photonic lifetime, spectral spacing and footprint independents. The applications of these PMs in optical processing signal were also demonstrate in this work. We demonstrate the use of the doublet splitting for 34.2 GHz RF signal extraction by filtering the sidebands of a modulated optical signal. We also demonstrate that very compact optical modulators operating 2.75 times beyond its resonator linewidth limit may be obtained using the PM triplet splitting, with separation of ~ 55 GHz. Finally, using the quadruplet of resonances, we demonstrate four-channel all-optical wavelength multicasting using only 1 mW of control power, with converted channel spacing of 40-60 GHz / Doutorado / Física / Doutor em Ciências

The present master's thesis deals with numerical modeling of solid-state micrometrical-sized polymeric dye lasers, commonly denoted as microcavities. It is part of a large research initiative carried out in the optics group, at the MAP (Microelectronics and Applied Physics) department in KTH (Kungliga Tekniska Högskolan - Royal Technical School) and targeted towards the design and manufacturing of micro- and nano-scaled polymeric components for nano-photonics, primarily lasers. The finite element method (FEM) in frequency domain is used as a primary modeling tool through the simulation software COMSOL Multiphysics. Models for spontaneous emission, optical losses and gain are developed and demonstrated. A specic layout is studied: the double hexagonal microcavity. While it was expected to be a good candidate for a laser, the design shows unexpected properties making it useful for sensing applications. Finally, the transposition of models to time domain is initiated : a replacement solution for the lacking perfectly matched layer (PML) in Comsol is developed and demonstrated. Methods for modeling materials parameters in time domain are investigated, together with the possible use of a more suitable algorithm : finite dierences in time domain (FDTD) or Yee's scheme.

The PhD dissertation is organized in two parts. In the first part, we present an experimental study of stimulated Raman scattering in a silicon-on-insulator (SOI) nanowire. We demonstrate that the Raman amplification of a narrow-band Stokes wave experiences a saturation effect for high pump intensities because of self phase modulation of the pump beam. Moreover, an analytical model is presented that describes the experimental results remarkably well. The model furthermore provides an estimation of the Raman gain coefficient γR of silicon. The second part is devoted to the experimental study of stimulated Raman scattering in a doubly resonant planar GaAs microcavity. The nonlinear measurements clearly show some totally unexpected results. We experimentally demonstrate that the relaxation of the electrons in the conduction band of GaAs is significantly modified through the interaction with coherently excited Raman phonons.

Orientador: Odilon Divino Damasceno Couto Júnior / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-08-28T03:39:00Z (GMT). No. of bitstreams: 1 Covacevice_AllanCassioTrevelin_M.pdf: 15137963 bytes, checksum: 6269264b01d872c4b40e0034a1575cf5 (MD5) Previous issue date: 2015 / Resumo: Neste trabalho, implementamos cálculos feitos através do método de elementos finitos no estudo de propriedades mecânicas e ópticas de microcavidades ópticas planares (POMCs) quando estas estão sob os efeitos de modulação induzidos por ondas acústicas de superfície (SAWs). Começamos resolvendo separadamente os problemas de modulação mecânica e caracterização de modos ópticos. Após isso, fundimos esses dois modelos em um terceiro, permitindo a caracterização da modulação acusto-óptica do sistema, o que nos permite também calcular as alterações induzidas nas propriedades ópticas das POMCs devido às SAWs. Concentramos nossa atenção em POMCs que possuem refletores de Bragg (DBRs) compostos por camadas de materiais fortemente piezoelétricos, como o ZnO e o LiNbO3. Mostramos que, usando em torno de 10 DBRs acima e abaixo da cavidade óptica, POMCs baseadas em ZnO/SiO2 e LiNbO3/SiO2 poderiam, em princípio, apresentar fatores de qualidade excedentes a 104. O alto confinamento de luz na cavidade permite-nos observar efeitos relacionados ao forte acoplamento fóton-fônon induzido pelas SAWs. Em particular, mostramos como a presença de SAWs confere a formação de super-redes ópticas dinâmicas induzidas acusticamente, as quais são caracterizadas pela dobradura ("folding") da dispersão dos fótons na cavidade, e pelo surgimento de "mini" zonas de Brillouin. Nossos resultados estão de acordo com resultados experimentais presentes na literatura. Eles abrem a possibilidade de caracterização de modulações acusticamente induzidas em sistemas de camadas arbitrários e criam uma plataforma muito boa para interpretação de resultados experimentais / Abstract: In this work, we implement finite element method calculations to study the mechanical and optical properties of planar optical microcavities (POMCs) under the strain modulation induced by surface acoustic waves (SAWs). We start by solving separately the problems of mechanical modulation and optical mode characterization. Afterwards, we merge the two models in a single one which enables the characterization of the acousto-optic modulation in the system and allows us to calculate the SAW induced modification in the optical properties of POMCs. We concentrate our attention in POMCs which have distributed Bragg reflectors (DBRs) composed of layers of highly piezoelectric materials like ZnO and LiNbO3. We show that, using around 10 DBRs on top and below the optical cavity layer, POMCs based on ZnO/SiO2 and LiNbO3/SiO2 could, in principle, have Q-factors exceeding 104. The strong light confinement in the cavity allows us to the observe effects related to the strong photon-phonon coupling induced by the SAW. In particular, we show how the presence of SAWs leads to the formation of acoustically induced dynamic optical superlattices, which are characterized by the folding of photon dispersion in the cavity and the appearance of "mini" Brillouin zones. Our results are in very good agreement with experimental results reported in literature. They open the possibility of characterization of acoustically induced modulation in arbitrary layered systems and create a very good platform for interpretation of experimental results / Mestrado / Física / Mestre em Física / 2013/118635-2 / 2012/11382-9 / CAPES / FAPESP

Estruturas fotônicas à base de silício têm despertado grande interesse por permitirem uma perfeita integração entre processos ópticos e eletrônicos em um único chip. Além de compatíveis com a atual indústria microeletrônica, acredita-se, que tais estruturas possam aumentar consideravelmente a velocidade de processamento de informações. Uma microcavidade óptica é um exemplo de estrutura fotônica simples. Feita à base de silício, e dopada com íons terra-rara, tal microcavidade pode intensificar a emissão gerada pelo íon e resultar em um dispositivo de importância tecnológica. O projeto-construção deste tipo de microcavidade deve considerar a sua região de funcionamento e os materiais a serem utilizados. Deve contemplar, ainda, algumas condições externas que, eventualmente, possam alterar o seu funcionamento. Uma dessas condições é descrita pelo chamado coeficiente termo-óptico que indica a dependência do índice de refração com a temperatura. Dentro desse contexto a presente Tese de Doutorado foi dedicada ao estudo de microcavidades ópticas com janelas de transmissão em 650 nm e em 1550 nm – correspondendo às regiões de menores perdas de fibras ópticas de plástico e de sílica. As microcavidades compreenderam espelhos de Bragg [camadas alternadas de silício amorfo (a-Si) e nitreto de silício amorfo (a-SiN)], um filme de a-SiN como espaçador, e foram depositadas sobre substratos de sílica pela técnica de sputtering. As cavidades MC-Er e MC-ErYb tiveram como espaçadores filmes de a-SiN dopados com Er e Er + Yb, respectivamente. Medidas de fotoluminescência da MC-ErYb na região do infravermelho próximo indicaram um aumento de 48 vezes na emissão dos íons Er3+ (em ~1535 nm) comparado a um filme de a-SiN dopado com érbio devido: (1) a presença do itérbio e, (2) às múltiplas reflexões sofridas pela luz nos espelhos de Bragg. As microcavidades cujos espaçadores eram a-SiN puro foram submetidas a medidas de transmissão óptica em função da temperatura de medida. O deslocamento da janela de transmissão devido às variações de temperatura permitiu determinar o valor do TOC do a-SiN como: (6.2±0.1)×10-5 ºC-1 (em ~ 620 nm) e, (4.7±0.1)×10-5 ºC -1 (em ~ 1510 nm). Até onde sabemos, o TOC do a-SiN no VIS foi determinado pela primeira vez neste trabalho. / Silicon photonic based structures have attracted great interest for allowing a perfect integration between optical and electronic process in a single chip. Besides being compatible with the actual microelectronic industry, it is believed that such structures can considerably increase the information processing speed. An optical microcavity is an example of a simple photonic structure. Made based on silicon, and doped with rare-earth ions, such microcavity may enhance the emission generated by the ion and become a device of technological importance. The project-construction of this kind of microcavity has to consider the operation region and the materials used. It still has to take into account external conditions that may, eventually, change its operation. One of these conditions is described by the thermo-optic coefficient (TOC) that shows the dependence of the refractive index with the temperature. Within this context the present PhD thesis was dedicated to the study of optical microcavities with transmission windows at 650 nm and at 1550 nm – corresponding to the low losses regions of the plastic and silica optical fibers. The microcavities comprised Bragg mirrors [alternated layers of amorphous silicon (a-Si) and amorphous silicon nitride (a-SiN)], one film of a-SiN as spacer, and were deposited on silica substrates by the sputtering technique. The MC-Er and MC-ErYb cavities had Er and Er+Yb-doped a-SiN films as spacers, respectively. Photoluminescence measurements of the MC-ErYb in the near infrared showed an enhancement of 48 times in the emission of the Er3+ ions (at ~ 1535 nm) compared with an Er-doped a-SiN film owing to: (1) the presence of ytterbium and, (2) the multiple reflections experienced by the light at the Bragg mirrors. The microcavities whose spacers were pure a-SiN were submitted to optical transmission measurements as a function of the measurement temperature. The shift of the transmission window due to variations in the temperature allowed determining the a-SiN TOC: (6.2±0.1)×10-5 ºC-1 (at ~ 620 nm) and, (4.7±0.1)×10-5 ºC -1 (at ~ 1510 nm). To the best of our knowledge, the a-SiN TOC in the visible was determined for the first time in this work.

Orientador: Newton Cesário Frateschi / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-08-17T01:57:53Z (GMT). No. of bitstreams: 1 Barea_LuisAlbertoMijam_M.pdf: 3934128 bytes, checksum: 9cd5c7861ac2af0dc42057f7f99ef89b (MD5) Previous issue date: 2010 / Resumo: As micro-cavidades ópticas são componentes essenciais em sistemas ópticos integrados, pois elas permitem capturar seletivamente, liberar e armazenar fótons, além de promoverem suas interações. Como exemplo, os micro-discos e micro-anéis são elementos que proporcionam tempos de vidas fotônicos extremamente longos, que podem ser utilizados tanto para filtros espectrais quanto para interações de fótons com alta eficiência não linear. Seu pequeno volume e seu alto tempo de vida fotônico são importantes para promoção eficiente de efeitos ópticos não lineares e, especialmente, o processo de mistura de quatro ondas com uma única freqüência de bombeio. No entanto, acoplar luz em um ressonador ainda é realizado com integrações híbridas utilizando fibras estranguladas. Nesta dissertação, nós apresentamos uma nova técnica para a fabricação de estruturas com ressonadores integrados monoliticamente a guias de ondas planares estrangulados, baseados em camadas de Si3N4/SiO2 depositadas sobre silício. Para isto, foi utilizada uma técnica que combina a nano fabricação, baseada em corrosões com um feixe de íons focalizados (FIB), com a técnica convencional de micro fabricação. Utilizando esta combinação, foi possível fabricar ressonadores acoplados a guias de ondas estrangulados e caracterizá-los. Para finalizar, nós observamos a geração de fótons em uma ressonância de um micro-anel devido ao efeito não linear de mistura de quatro ondas gerada pelo bombeio em uma ressonância subseqüente do anel / Abstract: Optical microcavities are essential components in optical integrated systems for they provide selective capture, release, and storage of photons as well as interaction with matter and other photons. As an example, micro-disks and micro-rings are elements that provide extremely long photon lifetime that can be used for spectral filtering as well for highly efficient non-linear photon interaction. For instance, its small volume and the high photonic lifetime are very important for the efficient promotion of nonlinear effects and, specially, the four wave-mixing (FWM) process with a single pumping frequency. However, coupling light to and from the resonator is still achieved with hybrid integration using tapered silica fibers. But, in this dissertation, we present a new technique for the fabrication of structures with monolithically integrated resonators and planar tapered waveguides, all based in Si3N4/SiO2 layers deposited on silicon. We use an approach that combines nano fabrication techniques based on focused ion beam (FIB) milling and conventional micro fabrication techniques. Using this approach, we could fabricate resonators coupled to tapered waveguides and characterize them. Finally, we observed the photon generation at a micro-ring resonance due to four-wave mixing generated by pumping at a subsequent micro-ring resonance / Mestrado / Física da Matéria Condensada / Mestre em Física

Estruturas fotônicas à base de silício têm despertado grande interesse por permitirem uma perfeita integração entre processos ópticos e eletrônicos em um único chip. Além de compatíveis com a atual indústria microeletrônica, acredita-se, que tais estruturas possam aumentar consideravelmente a velocidade de processamento de informações. Uma microcavidade óptica é um exemplo de estrutura fotônica simples. Feita à base de silício, e dopada com íons terra-rara, tal microcavidade pode intensificar a emissão gerada pelo íon e resultar em um dispositivo de importância tecnológica. O projeto-construção deste tipo de microcavidade deve considerar a sua região de funcionamento e os materiais a serem utilizados. Deve contemplar, ainda, algumas condições externas que, eventualmente, possam alterar o seu funcionamento. Uma dessas condições é descrita pelo chamado coeficiente termo-óptico que indica a dependência do índice de refração com a temperatura. Dentro desse contexto a presente Tese de Doutorado foi dedicada ao estudo de microcavidades ópticas com janelas de transmissão em 650 nm e em 1550 nm – correspondendo às regiões de menores perdas de fibras ópticas de plástico e de sílica. As microcavidades compreenderam espelhos de Bragg [camadas alternadas de silício amorfo (a-Si) e nitreto de silício amorfo (a-SiN)], um filme de a-SiN como espaçador, e foram depositadas sobre substratos de sílica pela técnica de sputtering. As cavidades MC-Er e MC-ErYb tiveram como espaçadores filmes de a-SiN dopados com Er e Er + Yb, respectivamente. Medidas de fotoluminescência da MC-ErYb na região do infravermelho próximo indicaram um aumento de 48 vezes na emissão dos íons Er3+ (em ~1535 nm) comparado a um filme de a-SiN dopado com érbio devido: (1) a presença do itérbio e, (2) às múltiplas reflexões sofridas pela luz nos espelhos de Bragg. As microcavidades cujos espaçadores eram a-SiN puro foram submetidas a medidas de transmissão óptica em função da temperatura de medida. O deslocamento da janela de transmissão devido às variações de temperatura permitiu determinar o valor do TOC do a-SiN como: (6.2±0.1)×10-5 ºC-1 (em ~ 620 nm) e, (4.7±0.1)×10-5 ºC -1 (em ~ 1510 nm). Até onde sabemos, o TOC do a-SiN no VIS foi determinado pela primeira vez neste trabalho. / Silicon photonic based structures have attracted great interest for allowing a perfect integration between optical and electronic process in a single chip. Besides being compatible with the actual microelectronic industry, it is believed that such structures can considerably increase the information processing speed. An optical microcavity is an example of a simple photonic structure. Made based on silicon, and doped with rare-earth ions, such microcavity may enhance the emission generated by the ion and become a device of technological importance. The project-construction of this kind of microcavity has to consider the operation region and the materials used. It still has to take into account external conditions that may, eventually, change its operation. One of these conditions is described by the thermo-optic coefficient (TOC) that shows the dependence of the refractive index with the temperature. Within this context the present PhD thesis was dedicated to the study of optical microcavities with transmission windows at 650 nm and at 1550 nm – corresponding to the low losses regions of the plastic and silica optical fibers. The microcavities comprised Bragg mirrors [alternated layers of amorphous silicon (a-Si) and amorphous silicon nitride (a-SiN)], one film of a-SiN as spacer, and were deposited on silica substrates by the sputtering technique. The MC-Er and MC-ErYb cavities had Er and Er+Yb-doped a-SiN films as spacers, respectively. Photoluminescence measurements of the MC-ErYb in the near infrared showed an enhancement of 48 times in the emission of the Er3+ ions (at ~ 1535 nm) compared with an Er-doped a-SiN film owing to: (1) the presence of ytterbium and, (2) the multiple reflections experienced by the light at the Bragg mirrors. The microcavities whose spacers were pure a-SiN were submitted to optical transmission measurements as a function of the measurement temperature. The shift of the transmission window due to variations in the temperature allowed determining the a-SiN TOC: (6.2±0.1)×10-5 ºC-1 (at ~ 620 nm) and, (4.7±0.1)×10-5 ºC -1 (at ~ 1510 nm). To the best of our knowledge, the a-SiN TOC in the visible was determined for the first time in this work.

Optical microcavities (OMs) are receiving increasing attention owing to their potential applications ranging from cavity quantum electrodynamics, optical detection to photonic devices. Recently, rolled-up structures have been demonstrated as OMs which have gained considerable attention owing to their excellent customizability. To fully exploit this customizability, asymmetric and topological rolled-up OMs are proposed and investigated in addition to conventional rolled-up OMs in this thesis. By doing so, novel phenomena and applications are demonstrated in OMs. The fabrication of conventional rolled-up OMs is presented in details. Then, dynamic mode tuning by a near-field probe is performed on a conventional rolled-up OM. Next, mode splitting in rolled-up OMs is investigated. The effect of single nanoparticles on mode splitting in a rolled-up OM is studied. Because of a non-synchronized oscillating shift for different azimuthal split modes induced by a single nanoparticle at different positions, the position of the nanoparticle can be determined on the rolled-up OM. Moreover, asymmetric rolled-up OMs are fabricated for the purpose of introducing coupling between spin and orbital angular momenta (SOC) of light into OMs. Elliptically polarized modes are observed due to the SOC of light. Modes with an elliptical polarization can also be modeled as coupling between the linearly polarized TE and TM mode in asymmetric rolled-up OMs. Furthermore, by adding a helical geometry to rolled-up structures, Berry phase of light is introduced into OMs. A -π Berry phase is generated for light in topological rolled-up OMs so that modes have a half-integer number of wavelengths. In order to obtain a deeper understanding for existing rolled-up OMs and to develop the new type of rolled-up OMs, complete theoretical models are also presented in this thesis.

Optical microcavities (OMs) are receiving increasing attention owing to their potential applications ranging from cavity quantum electrodynamics, optical detection to photonic devices. Recently, rolled-up structures have been demonstrated as OMs which have gained considerable attention owing to their excellent customizability. To fully exploit this customizability, asymmetric and topological rolled-up OMs are proposed and investigated in addition to conventional rolled-up OMs in this thesis. By doing so, novel phenomena and applications are demonstrated in OMs. The fabrication of conventional rolled-up OMs is presented in details. Then, dynamic mode tuning by a near-field probe is performed on a conventional rolled-up OM. Next, mode splitting in rolled-up OMs is investigated. The effect of single nanoparticles on mode splitting in a rolled-up OM is studied. Because of a non-synchronized oscillating shift for different azimuthal split modes induced by a single nanoparticle at different positions, the position of the nanoparticle can be determined on the rolled-up OM. Moreover, asymmetric rolled-up OMs are fabricated for the purpose of introducing coupling between spin and orbital angular momenta (SOC) of light into OMs. Elliptically polarized modes are observed due to the SOC of light. Modes with an elliptical polarization can also be modeled as coupling between the linearly polarized TE and TM mode in asymmetric rolled-up OMs. Furthermore, by adding a helical geometry to rolled-up structures, Berry phase of light is introduced into OMs. A -π Berry phase is generated for light in topological rolled-up OMs so that modes have a half-integer number of wavelengths. In order to obtain a deeper understanding for existing rolled-up OMs and to develop the new type of rolled-up OMs, complete theoretical models are also presented in this thesis.