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Publications

Publications by CAP

2019

Evaluation of Nanoplasmonic Optical Fiber Sensors Based on D-Type and Suspended Core Fibers with Metallic Nanowires

Authors
Santos, D; Guerreiro, A; Baptista, JM;

Publication
PHOTONICS

Abstract
The introduction of metallic nanostructures in optical fibers has revolutionized the field of plasmonic sensors since they produce sharper and fine-tuned resonances resulting in higher sensitivities and resolutions. This article evaluates the performance of three different plasmonic optical fiber sensors based on D-type and suspended core fibers with metallic nanowires. It addresses how their different materials, geometry of the components, and their relative position can influence the coupling between the localized plasmonic modes and the guided optical mode. It also evaluates how that affects the spatial distributions of optical power of the different modes and consequently their overlap and coupling, which ultimately impacts the sensor performance. In this work, we use numerical simulations based on finite element methods to validate the importance of tailoring the features of the guided optical mode to promote an enhanced coupling with the localized modes. The results in terms of sensitivity and resolution demonstrate the advantages of using suspended core fibers with metallic nanowires.

2019

High performance solver of the multidimensional generalized nonlinear Schrodinger equation with coupled fields

Authors
Ferreira, TD; Silva, NA; Guerreiro, A;

Publication
FOURTH INTERNATIONAL CONFERENCE ON APPLICATIONS OF OPTICS AND PHOTONICS

Abstract
We report on the development of numerical module for the HiLight simulation platform based on GPGPU supercomputing to solve a system of coupled fields governed by the Generalized Nonlinear Schrodinger Equation with local and/or nonlocal nonlinearities. This models plays an important role in describing a plethora of different phenomena in various areas of physics. In optics, this model was initially used to describe the propagation of light through local and/or nonlocal systems under the paraxial approximation, but more recently it has been extensively used as a support model to develop optical analogues. However, establishing the relation between the original system and the analogue, as well as, between their model and the actual experimental setup is not an easy task. First and foremost because in most cases the governing equations are nonintegrable, preventing from obtaining analytical solutions and hindering the optimization of the experiments. Alternatively, despite numerical methods not providing exact solutions, they allow to test different experimental scenarios and provide a better insight to what to expect in an actual experiment, while giving access to all the variables of the optical system being simulated. However, the numerical solution of a system of N-coupled Schrodinger fields in systems with two or three spatial dimensions requires massive computation resources, and must employ advanced supercomputing and parallelization techniques, such as GPGPU. This paper focuses on the numerical aspects behind this challenge, describing the structure of our simulation module, its performance and the tests performed.

2019

HILIGHT: A NEW SIMULATION PLATFORM FOR ADVANCED PHOTONICS

Authors
Guerreiro, A; Silva, NA; Costa, J; Gomes, M; Alves, R; Ferreira, TD; Madureira, IS; Pereira, AAM; Almeida, AL;

Publication
FOURTH INTERNATIONAL CONFERENCE ON APPLICATIONS OF OPTICS AND PHOTONICS

Abstract
We report on the development of HiLight, a new multiphysics simulation platform for advanced photonics with interactive modules dedicated to the study of the propagation of light in multitude of spatially structured optical media, including nonlocal and nonlinear media, optical lattices with atomic gases and plasmas, among others.

2019

A Simple Spectral Interrogation System for Optical Fiber Sensors

Authors
Santos,; Jorge,; Almeida,; Coelho,;

Publication
Proceedings

Abstract
Optical fiber sensors (OFS) based on long-period fiber gratings (LPFG) or on surface plasmon resonance (SPR) represent attractive solutions for detection systems in remote areas. An interrogation system consisting on wavelength modulation of fiber coupled distributed feedback (DFB) lasers was implemented and tested. The system uses a single photodetector to individually acquire the intensity of each DFB laser modulated by the OFS and the real transmission spectrum is reconstructed through curve fitting. Testing was accomplished by measuring the spectral features of an LPFG when changing the surrounding refractive index and errors lower than 1.8 nm in the 1530 to 1570 nm wavelength region were obtained.

2019

Evaluation of food labelling usefulness for consumers

Authors
Moreira, MJ; Garcia Diez, J; de Almeida, JMMM; Saraiva, C;

Publication
INTERNATIONAL JOURNAL OF CONSUMER STUDIES

Abstract
Food labelling is a means of communication between food business operators and consumers, representing an important factor in consumer purchasing decisions. The enforcement of the new food labelling policy is aimed to improve food safety and public health through the mandatory indication of information and nutritional values. To understand the usefulness of the information provided for consumers, a survey was carried out to assess the efficacy of the information presented in food labelling. Principal component analysis was performed to obtain a smaller number of uncorrelated factors regarding the usefulness of food labelling. Results showed consumers usually do not read food labels due to lack of time and excessive information. Additionally, food labelling was observed to be more useful for specific consumer groups, such as, athletes, consumers with health conditions or consumers concerned with a healthy lifestyle. The results of the present study highlight the need of information campaigns by public health authorities to show the importance and advantages of reading food labels as well as the development of essential information which should be quickly and clearly seen and understood by consumers.

2019

Addressing the Fabrication Difficulties of Femtosecond Laser Written Surface Waveguides for Enhanced Evanescent Coupling

Authors
Amorim, VA; Maia, JM; Viveiros, D; Marques, PVS;

Publication
EPJ Web of Conferences

Abstract
In this work, the fabrication of optical waveguides embedded in fused silica (Suprasil1) and boro-aluminosilicate glass (Eagle2000) is demonstrated with femtosecond laser direct writing, as well as their suitability to be brought to the surface, through wet etching, for enhanced evanescent coupling with the external dielectric medium. Fused silica demonstrated to be inappropriate in this particular application, as the guiding region is at the bottom of the induced modification, creating a barrier between the guided mode and the substrate’s boundary. Furthermore, the existence of nanogratings meant that, upon contact of the top of the induced modification with the substrate’s boundary, the waveguide is quickly etched. Eagle2000 demonstrated to be superior to fused silica due to its characteristic modification cross-section and absence of nanogratings, which allowed the placement of the guiding region as close to the substrate’s surface as required. However, surface roughness arising from the creation of insoluble products in the HF solution was found. The addition of HCl to dissolve these products was implemented.

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