Optical devices based on photonic crystal fibers with integrated electrodes

Orientador: Cristiano Monteiro de Barros CordeiroDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Fisica "Gleb Wataghin"Resumo: Neste trabalho de mestrado apresentamos o estudo e desenvolvimento de dispositivos óticos totalmente à fibra. Para isso, exploramos as novas possibilidades trazidas pelo advento das fibras de cristal fotônico (PCF's, do inglês Photonic Crystal Fibers). As PCF's são uma classe especial de fibras óticas que apresentam uma estrutura regular de buracos de ar na sua seção transversal, semelhante a um cristal fotônico. As fibras de cristal fotônico, além de apresentarem as vantagens inerentes às fibras óticas tradicionais, possuem novos graus de liberdade intrínsecos. Entre eles, o mais importante é a possibilidade de alterar fortemente as características da fibra através, apenas, do arranjo de buracos. Aqui, desenvolvemos uma fibra de cristal fotônico com dois buracos externos à microestrutura para integração de eletrodos. Posteriormente, um desses eletrodos foi exposto, polindo-se a lateral da fibra, e contato elétrico foi realizado. O elemento de controle do dispositivo ótico é a corrente elétrica que, aplicada ao eletrodo, o esquenta e o faz expandir via efeito Joule. O aumento de temperatura e a compressão causada pela expansão do eletrodo alteram o índice de refração e, portanto, a birrefringência da fibra. Foram realizadas, ainda, simulações utilizando o software comercial Comsol Multiphysics com o objetivo de entender a influência da temperatura e da compressão mecânica no modo ótico guiado pela fibra, bem como encontrar maneiras de otimizar o dispositivo em questãAbstract: In this work we present a study and the development of all-fiber optical devices. For this purpose we exploited the new possibilities brought by the development of Photonic Crystal Fibers. PCF's are special kind of optical fibers with a regular pattern of air holes in their transverse section, resembling a photonic crystal. Photonic Crystal Fibers not only have the inherent advantages of traditional optical fibers but they have new intrinsic degrees of freedom. Among them, we can quote the possibility of strongly altering the fiber characteristics through the design of the air holes pattern. Here, we developed a photonic crystal fiber with two extra holes for electrode integration. One of these electrodes was exposed by side polishing the fiber and electrical contact to an external circuit was made. The contrai element of the optical device is the electrical current which, when applied to the electrode, heats it up and make it expand by Joule effect. The temperature increase and the compression caused by the electrode expansion alter the refractive index and, consequently, the fiber birefringence. We algo numerically studied the problem through Com sol software. The objective here was to understand the influence of temperature and stress on the light guided mode. In conclusion, we demonstrated in this work the creation of an all-fiber device based on the integration of electrodes to photonic crystal fibers where the element of contrai is the electrical current applied to the electrodes. We algo studied how to improve the parameters concerning the device operationMestradoFísica GeralMestre em Físic

Specialty optical fibers for sensing

Orientador: Cristiano Monteiro de Barros CordeiroTese (doutorado) - Universidade Estadual de Campinas, Instituto de Física Gleb WataghinResumo: No trabalho aqui apresentado, fibras ópticas especiais foram fabricadas e estudadas para fins de sensoriamento de corrente elétrica e campo magnético. Primeiramente, propusemos e fabricamos uma fibra óptica especial com dois tipos de birrefringência: linear e circular. Para a adição de birrefringência linear, um padrão de buracos levemente assimétrico, de modo a produzir um núcleo elíptico, foi empregado. Para a adição de birrefringência circular, adotamos a estratégia de imprimir uma torção na fibra durante sua fabricação. Essa fibra óptica especial foi modelada, fabricada e analisada teórica (método dos elementos finitos) e experimentalmente (modos guiados, perda, birrefringência) A aplicação da fibra especial com taxa de torção como sensor de corrente elétrica se baseou no efeito Faraday, em que a luz tem seu estado de polarização alterado ao atravessar uma região sob a influência de um campo magnético. Para o estabelecimento do sensor foi utilizado um método de interrogação polarimétrico com luz linearmente polarizada. Obtivemos uma sensibilidade de (1,00 ± 0,04) x 10-5 A-1 e, mais importante, demonstramos que o procedimento de adicionar birrefringência circular à fibra torna-a menos sensível a perturbações externas, em especial, ao efeito da birrefringência linear induzida pela curvatura da fibra. Ainda no âmbito de sensoriamento de corrente elétrica e campo magnético, discutimos alguns sensores utilizando fibras convencionais, com redes de Bragg e filmes finos de terfenol-D (material magnetostritivo). Por fim, desenvolvemos um sensor de temperatura empregando uma fibra capilar com núcleo imerso na parede (embedded-core fiber) e preenchida com material metálico (índio). Com este sensor, obtivemos uma sensibilidade de (8,40 ± 0,06) nm.°C-1, valor comparável aos mais elevados encontrados na literaturaAbstract: In this work, specialty optical fibers were developed and studied for electric current and magnetic field sensing. First we proposed and fabricated an optical fiber with linear and circular birefringences. To create the linear birefringence a slightly asymmetric pattern of air holes was used to produce an elliptical core. In order to add circular birefringence to the fiber we developed a mechanism to spun the fiber during its fabrication. This specialty optical fiber was theoretically (finite elements method) and experimentally (guided modes, loss and birefringences) analyzed. Using the spun fiber as an electric current sensor was based on the Faraday effect, where light has its polarization changed when travelling through a region under the influence of a magnetic field. To establish the sensor we used a polarimetric interrogation system with linearly polarized light. Here we obtained a sensitivity of (1,00 ± 0,04) x 10-5 A-1 and, most importantly, we demonstrated that the procedure of adding circular birefringence to the fiber makes it less sensitive to external perturbations, such as the effect of the linear birefringence induced by curvature. Regarding electric current and magnetic field sensing, we studied some configurations using a conventional optical fiber, with an inscripted FBG and a thin film of magnetosctrictiv material, terfenol-D. Finally, we developed a temperature sensor by employing a embedded-core fiber filled with índium. With this sensor we obtained a sensitivity of (8,40 ± 0,06) nm.°C-1, which is comparable to the highest reported valuesDoutoradoFísicaDoutor em Ciências797088/2009CAPE

Analysis And Optimization Of An All-fiber Device Based On Photonic Crystal Fiber With Integrated Electrodes.

We present both numerical and experimental studies of an all-fiber device based on the integration of metallic electrodes into photonic crystal fibers (PCF). The device operation consists on applying electrical current to the electrodes which, by Joule effect, expand and squeeze the PCF microstructure in a preferential direction, altering both phase and group birefringence. We investigate the effect of integrating electrodes into the fiber and the dependence of the device sensitivity on the electrode configuration and composition.182842-

Bragg gratings in surface-core fibers: refractive index and directional curvature sensing

FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPFINANCIADORA DE ESTUDOS E PROJETOS - FINEPCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQIn this paper, we report, to our knowledge, the first extended study of the inscription of Bragg gratings in surface-core fibers and their application in refractive index and directional curvature sensing. The research ranges from fiber fabrication and grating inscription in untapered and tapered fibers to the performance of simulations and sensing measurements. Maximum sensitivities of 40 nm/RIU and 202.7 pm/ m (1) were attained in refractive index and curvature measurements respectively. The obtained results compares well to other fiber Bragg grating based devices. Ease of fabrication, robustness and versatility makes surface-core fibers an interesting platform when exploring fiber sensing devices. (C) 2017 Elsevier Inc. All rights reserved.In this paper, we report, to our knowledge, the first extended study of the inscription of Bragg gratings in surface-core fibers and their application in refractive index and directional curvature sensing. The research ranges from fiber fabrication and grating inscription in untapered and tapered fibers to the performance of simulations and sensing measurements. Maximum sensitivities of 40 nm/RIU and 202.7 pm/ m (1) were attained in refractive index and curvature measurements respectively. The obtained results compares well to other fiber Bragg grating based devices. Ease of fabrication, robustness and versatility makes surface-core fibers an interesting platform when exploring fiber sensing devices.348690FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPFINANCIADORA DE ESTUDOS E PROJETOS - FINEPCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPFINANCIADORA DE ESTUDOS E PROJETOS - FINEPCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ2014/50632-601.12.0393.00Sem informaçãoThis research was funded by grant #2014/50632-6 from Sao Paulo Research Foundation (FAPESP) and FINEP (grant #01.12.0393.00). J. H. Osorio acknowledges Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq) and R. Oliveira acknowledges the National Funds through FCT-Fundacao para a Ciencia e Tecnologia under the project SFRH/BD/88472/2012 and UID/EEA/50008/2013 (Swat). The authors would like to thank J. A. Santos, A. C. Camillo and R. B. Borges for technical support

All-fiber Devices Based On Photonic Crystal Fibers With Integrated Electrodes.

A special kind of microstructured optical fiber is proposed and fabricated in which, in addition to the holey region (solid core and silica-air cladding), two large holes exist for electrode insertion. Either Bi-Sn or Au- Sn alloys were selectively inserted into the large holes forming two parallel, continuous and homogeneous internal electrodes. We demonstrate the production of a monolithic device and its use to externally control some of the guidance properties (e.g. polarization) of the fiber.171660-