The design, construction and characterisation of a novel, arrayed, open-access optical microcavity is described. Included in this thesis are the precise fabrication details, making use of the focused ion beam. A technique for analysing and optimising the microcavities constructed, making use of an atomic force microscope is also included. Results from the optical characterisation of the fabricated microcavities are presented, including quality factors of around 104, and fitnesses of around 400. The optical analysis then progressed onto coupling colloidal semiconductor nanocrystals to the microcavity modes. This yielded room temperature Purcell enhancements, single particle sensing, and also allowed for the characterisation of a second iteration of cavities. This improved set was shown to achieve fitnesses in excess of 1800 and quality factors with a lower limit of 15000. The optical identification of single NV centres in nanodiamond is discussed, along with the development of an optical apparatus to couple them to microcavities at cryogenic temperatures. Finally several results from finite difference time domain simulations will be presented, showing ultimate mode volumes of less than 0.5 cubic wavelengths are possible for this approach.

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.

No description available.

Cavity enhanced spectroscopies (CES) are currently amongst the most sensitive spectroscopic techniques available for probing gas-phase samples, however their application to the liquid-phase has been more limited. Sensitive analysis of submicrolitre liquid samples is highly desirable, as miniaturisation allows for the reaction and analysis of scarce or expensive reagents, produces less waste, and can increase the speed of separations and reactions, whilst having a small footprint and high throughput. Absorption spectroscopy is a particularly desirable technique due to its universal, label-free nature, however its application to small volume liquid samples is hampered by the associated short absorption pathlengths, which limit sensitivity. CES improve sensitivity by trapping light within a confined region, increasing the effective pathlength through the sample. Three distinct types of optical cavity were constructed and evaluated for the purposes of making optical absorption measurements on liquid samples. The first incorporated a high optical quality flow cell into a "macrocavity" formed from two dielectric mirrors separated by 51.3 cm. Cavity losses were minimised by positioning the flow cell at Brewster's angle to the optical axis, and the setup was used to perform a single-wavelength cavity ringdown spectroscopy experiment to detect and quantify nitrite within aqueous samples. The detection limit was determined to be 8.83 nM nitrite in an illuminated volume of only 74.6 nL. Scattering and reflective losses from the flow cell surfaces were found to be the largest barrier to increased sensitivity, leading us to focus on the integration of cavity mirrors within a microfluidic flow system in the work that followed. In the second set of experiments, cavity enhanced absorption spectroscopy (CEAS) measurements were performed on Thymol Blue using custom-made microfluidic chips with integrated cavity mirrors. Unfortunately, due to the plane-parallel configuration of the mirrors and the corresponding difficulty in sustaining stable cavity modes, the results were underwhelming, with a maximum cavity enhancement factor (CEF) of only 2.68. At this point, attention was focussed toward a more well-defined cavity geometry: open-access plano-concave microcavities. The microcavities consist of an array of micron-scale concave mirrors opposed by a planar mirror, with a pathlength that is tunable to sub-nanometer precision using piezoelectric actuators. In contrast to the other experimental setups described, themicrocavities allow for optical measurements to be performed in which we monitor the change of wavelength and/or amplitude of a single well-defined cavity mode in response to a liquid sample introduced between the mirrors. In the first microcavity experiment, we used 10 μm diameter mirrors with cavity lengths from 2.238 μm to 10.318 μm to demonstrate refractive index sensing in glucose solutions with a limit of detection of 3.5 x 10^-4 RIU. The total volume of detection in our setup was 54 fL. Thus, at the limit of detection, the setup can detect the change of refractive index that results from the introduction of 900 zeptomoles (500,000 molecules) of glucose into the device. The microcavity sensor was then adapted to enable broadband absorption measurements of methylene blue via CEAS. By recording data simultaneously from multiple cavities of differing lengths, absorption data is obtained at a number of wavelengths. Using 10 μm diameter mirrors with cavity pathlengths from 476 nm to 728 nm, a limit of detection, expressed as minimum detectable absorption per unit pathlength, of 1.71 cm^-1 was achieved within a volume of 580 attolitres, corresponding to less than 2000 molecules within the mode volume of the cavity. Finally, a new prototype was developed with improved cavity finesse, a much more intense and stable light source, and improved flow design. Using a single plano-concave microcavity within the array with a cavity pathlength of 839.7 nm, and 4 μm radius of curvature mirror, absorption measurements were performed on Methylene Blue. Analysis of this data indicated a CEF of around 9270, and a limit of detection based on the measured signal-to-noise ratio of 0.0146 cm^-1. This corresponds to a minimum detectable concentration of 104 nM Methylene Blue, which given the mode volume of 219 aL, suggests a theoretical minimum detectable number of molecules of 14.

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.

Following the intensive development of isolated (i.e., not coupled with on-chip waveguide) vertically rolled-up microtube ring resonators (VRU-MRRs) for both active and passive applications, a variety of microtube-based devices has been realized. These include microcavity lasers, optical sensors, directional couplers, and active elements in lab-on-a-chip devices. To provide more advanced and complex functionality, the focus of tubular geometry research is now shifting toward (i) refined vertical light transfer in 3D stacks of multiple photonic layers and (ii) to make microfluidic cooling system in the integrated optoelectronic system. Based on this motivation, this PhD research is devoted to the demonstration and the implementation of monolithic integration of VRU-MRRs with photonic waveguides for 3D photonic integration and their optofluidic applications. Prior to integration, high-quality isolated VRU-MRRs on the flat Si substrate are firstly fabricated by the controlled release of differentially strained titanium-dioxide (TiO2) bilayered nanomembranes. The fabricated microtubes support resonance modes for both telecom and visible photonics. The outcome of the isolated VRU-MRRs is a record high Q (≈3.8×10^3) in the telecom wavelength range with optimum tapered optical fiber resonator interaction. To further study the optical modes in the visible and near infrared spectral range, μPL spectroscopy is performed on the isolated VRU-MRRs, which are activated by entrapping various sizes of luminescent nanoparticles (NPs) within the windings of rolled-up nanomembranes based on a flexible, robust and economical method. Moreover, it is realized for the first time, in addition to serving as light sources that NPs-aggregated in isolated VRU-MRRs can produce an optical potential well that can be used to trap optical resonant modes. After achieving all the required parameters for creating a high-quality TiO2 VRU-MRR, the monolithic integration of VRU-MRRs with Si nanophotonic waveguides is experimentally demonstrated, exhibiting a significant step toward 3D photonic integration. The on-chip integration is realized by rolling up 2D pre-strained TiO2 nanomembranes into 3D VRU-MRRs on a microchip which seamlessly expanded over several integrated waveguides. In this intriguing vertical transmission configuration, resonant filtering of optical signals at telecom wavelengths is demonstrated based on ultra-smooth and subwavelength thick-walled VRU-MRRs. Finally, to illustrate the usefulness of the fully integrated VRU-MRRs with photonic waveguides, optofluidic functionalities of the integrated system is investigated. In this work, two methods are performed to explore optofluidic applications of the integrated system. First, the hollow core of an integrated VRU-MRR is uniquely filled with a liquid solution (purified water) by setting one end of the VRU-MRRs in contact with a droplet placed onto the photonic chip via a glass capillary. Second, the outside of an integrated VRU-MRR is fully covered with a big droplet of liquid. Both techniques lead to a significant shift in the WGMs (Δλ≈46 nm). A maximum sensitivity of 140 nm/refractive index unit, is achieved. The achievements of this PhD research open up fascinating opportunities for the realization of massively parallel optofluidic microsystems with more functionality and flexibility for analysis of biomaterials in lab-on-a-tube systems on single chips. It also demonstrates 3D photonic integration in which optical interconnects between multiple photonic layers are required.

In my thesis I will discuss some aspects of collective dynamics of excitons and exciton-polaritons in nanoscale heterostructures. In the first Chapter I will make a brief introduction to the modern semiconductor physics and willdescribe the general elements and notions which will be used further. Other four chapters would be devoted to four works in which I participated, notably, in Chapter 2 I will speak about the coherent interactions between phonons and exciton orexciton-polariton condensates, in Chapter 3 I will discuss the quantum dots lasing and its amplification by an acoustic pulse. Chapter 4 and 5 will be devoted respectively to the polariton multistability and to the condensates of indirect excitons.

Le phénomène d’up-conversion de photon (UpC) permet de générer de la lumière à longueurs d’onde plus courtes que la longueur d’onde d’excitation. Dans cette recherche, la synthese de couches minces dopées avec des ions de terres rares (RE3+) optiquement actifs, leurs caractérisations structurales, ainsi que leurs propriétés optiques et de photoluminescentes ont été étudiées. Les couches ont été élaborées par deux voies de dépôt de couche sur du silicium et des substrats transparents: tout d’abord, un dépôt chimique organométallique en phase vapeur (LI-MOCVD, AA-MOCVD) est utilisé pour le dépôt des couches minces de YF3 et Y2O3 co-dopées Er/Yb. Il est démontré que l’émission d’UpC de Er3+ avec une excitation à 972 nm est influencée par le réseau hôte. Par ailleurs, le traitement sol-gel, une technique chimique par voie humide, est utilisé pour la fabrication de couches minces Y2O3, SiO2 et TiO2 co-dopées Er/Yb par spin-coating. Une optimisation de l’´emission de lumière par UpC a été atteinte grâce à l’ajustement de la concentration de RE et de la température de traitement thermique. De plus, une approche différente a été étudiée pour atteindre une émission UpC renforcée : l’utilisation de microcavités diélectriques de Fabry-Pérot obtenues par sol-gel, constitués d’un empilement de couches de silice et d’oxyde de titane, avec Er/Yb:Y2O3 comme couche de cavité. Le but de ce travail est de répondre aux questions suivantes: comment la nature du réseau hôte et le niveau de dopage influencent l’émission radiative de l’Er3+? Quelles sont les conditions pour un bon matériau d’UpC et ses limites? Nous incluons également une discussion sur les perspectives d’une application possible d’une couche d’UpC dans un dispositif de cellule solaire, qui pourrait améliorer la réponse dans l’infrarouge. / Photon up-conversion (UpC) allows the generation of light of shorter wavelengths compared to the excitation wavelength. In this work the synthesis of thin films doped with optically active rare earth (RE3+) ions, their structural characterization, as well the optical and photoluminescence properties are highlighted. The emphasis lies on two different routes of film deposition on silicon and transparent substrates: first, metalorganic chemical vapor deposition (LI-MOCVD, AA-MOCVD) is introduced for the deposition of Er/Yb-doped YF3 and Y2O3 films and it is demonstrated, how the UpC emission of Er3+ upon 972 nm excitation is influenced by the host lattice. Secondly, sol-gel processing, a wet-chemical technique, is used for the fabrication of Er/Yb-doped Y2O3, SiO2 and TiO2 thin films by spin-coating. Optimization of the up-converted light emission was achieved through adjusting the RE concentration and the processing temperature. Moreover, in a different approach for achieving an enhanced UpC emission, sol-gel derived Fabry-Pérot dielectric microcavities, consisting of a multilayer stack of silica and titania layers and Er/Yb: Y2O3 as the cavity layer, are investigated. The aim of this work is to address the questions, how does the nature of the host lattice and doping level influence the radiative emission in Er3+, what are the requirements for a good upconverter material and what are the limitations? We also include a discussion of the application of an upconverter to a solar cell device, which may debatably enhance the response in the infrared.