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Publications

Publications by Ariel Guerreiro

2015

On the anodic aluminium oxide refractive index of nanoporous templates

Authors
Hierro Rodriguez, A; Rocha Rodrigues, P; Valdes Bango, F; Alameda, JM; Jorge, PAS; Santos, JL; Araujo, JP; Teixeira, JM; Guerreiro, A;

Publication
JOURNAL OF PHYSICS D-APPLIED PHYSICS

Abstract
In the present study, we have determined the intrinsic refractive index of anodic aluminium oxide, which is originated by the formation of nanoporous alumina templates. Different templates have been fabricated by the conventional two-step anodization procedure in oxalic acid. Their porosities were modified by chemical wet etching allowing the tuning of their effective refractive indexes (air-filled nanopores + anodic aluminium oxide). By standard spectroscopic light transmission measurements, the effective refractive index for each different template was extracted in the VIS-NIR region. The determination of the intrinsic anodic aluminium oxide refractive index was performed by using the Maxwell-Garnett homogenization theory. The results are coincident for all the fabricated samples. The obtained refractive index (similar to 1.55) is quite lower (similar to 22%) than the commonly used Al2O3 handbook value (similar to 1.75), showing that the amorphous nature of the anodic oxide structure strongly conditions its optical properties. This difference is critical for the correct design and modeling of optical plasmonic metamaterials based on anodic aluminium oxide nanoporous templates.

2015

Optical Fiber Tweezers Fabricated by Guided Wave Photo-Polymerization

Authors
Ribeiro, RSR; Queiros, R; Soppera, O; Guerreiro, A; Jorge, PAS;

Publication
Photonics

Abstract

2016

Optical fibers as beam shapers: from Gaussian beams to optical vortices

Authors
Rodrigues Ribeiro, RSR; Dahal, P; Guerreiro, A; Jorge, P; Viegas, J;

Publication
OPTICS LETTERS

Abstract
This Letter reports a new method for the generation of optical vortices using a micropatterned optical fiber tip. Here, a spiral phase plate (2 pi phase shift) is micromachined on the tip of an optical fiber using a focused ion beam. This is a high resolution method that allows milling the fibers with nanoscale resolution. The plate acts as a beam tailoring system, transforming the fundamental guided mode, specifically a Gaussian mode, into the Laguerre-Gaussian mode (LG(01)), which carries orbital angular momentum. The experimental results are supported by computational simulations based on the finite-difference time-domain method. (C) 2016 Optical Society of America

2015

Polymeric Optical Fiber Tweezers as a tool for single cell micro manipulation and sensing

Authors
Rodrigues Ribeiro, RSR; Soppera, O; Guerreiro, A; Jorge, PAS;

Publication
24TH INTERNATIONAL CONFERENCE ON OPTICAL FIBRE SENSORS

Abstract
In this paper a new type of polymeric fiber optic tweezers for single cell manipulation is reported. The optical trapping of a yeast cell using a polymeric micro lens fabricated by guided photo polymerization at the fiber tip is demonstrated. The 2D trapping of the yeast cells is analyzed and maximum optical forces on the pN range are calculated. The experimental results are supported by computational simulations using a FDTD method. Moreover, new insights on the potential for simultaneous sensing and optical trapping, are presented.

2015

The efficiency of fiber optical tweezers for cell manipulation using distinct fabrication methods

Authors
Ribeiro, RSR; Soppera, O; Viegas, J; Guerreiro, A; Jorge, PAS;

Publication
COMPLEX LIGHT AND OPTICAL FORCES IX

Abstract
In this work, the trapping efficiency of new fiber optical tweezers structures fabricated using photo polymerization and focused ion beam milling techniques is evaluated. The first fabrication methods may present limited capabilities on the tailoring of the structures, and therefore limited operation features. On the other hand, with focused ion beam milling a vast myriad of structures may be accurately fabricated, and contrarily to conventional fabrication methods, more specialized manipulation tools can be developed. In this regard, the performance of FOT for the trapping of yeast cells using spherical lenses (photo polymerization) and spiral phase lenses (FIB) will be presented. In addition, finite difference time domain (FDTD) simulations of the full vectorial optical propagation through the designed structures and the corresponding calculation of the optical forces are presented and different designs are evaluated.

2014

Analysis of phase interrogation of SPR fiber optic sensors with characteristics tailored by the application of different metal-dielectric overlays

Authors
Moayyed, H; Leite, IT; Coelho, L; Santos, JL; Guerreiro, A; Viegas, D;

Publication
23RD INTERNATIONAL CONFERENCE ON OPTICAL FIBRE SENSORS

Abstract
Optical fiber sensors based on the phenomenon of plasmonic resonance can be interrogated applying different methods, the most common one being the spectral approach where the measurand information is derived from the reading of the wavelength resonance dip. In principle, a far better performance can be achieved considering the reading of the phase of the light at a specific wavelength located within the spectral plasmonic resonance. This approach is investigated in this work for fiber optic SPR sensors with overlays which are combinations of metallic and dielectric thin films, permitting not only to tune the wavelength of the SPR resonance but also the sensitivity associated with the phase interrogation of the sensors.

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