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Publicações

Publicações por Paulo Vicente Marques

2013

A LONG PERIOD GRATING-BASED PLATFORM FOR THE DETECTION OF E. COLI PROTEINS

Autores
Queiros, RB; Gouveia, C; Fernandes, JRA; Marques, PVS; Noronha, JP; Sales, MGF; Jorge, PAS;

Publicação
8TH IBEROAMERICAN OPTICS MEETING AND 11TH LATIN AMERICAN MEETING ON OPTICS, LASERS, AND APPLICATIONS

Abstract
A Long Period Grating (LPG)-based platform for the detection of E. coli outer membranes proteins (EcOMPs) is presented. The sensing probe is achieved by the functionalization of a LPG inscribed in a single mode fiber (SMF28) with a DNA-aptamer resulting in a label-free configuration capable of specific recognize EcOMPs in waters. Measurement takes place by tracking the variations induced in the resonance wavelength by the refractive index changes at the fiber surface (approximate to 100 nm/RIU). The sensing head was characterized and tested against EcOMPs and applied to spiked environmental water samples. The sensor displayed logarithmic responses in the range of 0.1 nM to 10 nM EcOMPs and is regenerated (under low pH conditions) and the deviation of the subsequent detection was less than 0.1%.

2017

Optimization of Broadband Y-Junction Splitters in Fused Silica by Femtosecond Laser Writing

Autores
Amorim, VA; Maia, JM; Alexandre, D; Marques, PVS;

Publicação
IEEE PHOTONICS TECHNOLOGY LETTERS

Abstract
Optical Y-junction power splitters owe their inherent broadband spectral behavior to their design. However, depending on the fabrication technique employed, asymmetries in the junction might arise, perturbing its performance; this is the case in femtosecond laser written Y-junctions where one arm is typically written over the top of the other. In this letter, the spectral behavior of Y-junctions fabricated in fused silica by the femtosecond laser direct writing technique was analyzed and optimized for the first time, to the best of our knowledge. The junction arms output power balance as well as the corresponding spectral flatness between 1300 and 1600 nm is substantially increased by the implementation of an initial separation between the arms at the junction diverging point, enabling the manufacturing of balanced broadband Y-junctions.

2017

Real-Time Optical Monitoring of Etching Reaction of Microfluidic Channel Fabricated by Femtosecond Laser Direct Writing

Autores
Maia, JM; Amorim, VA; Alexandre, D; Marques, PVS;

Publicação
JOURNAL OF LIGHTWAVE TECHNOLOGY

Abstract
Femtosecond laser direct writing is a three dimensional fabrication technique that can be applied to produce integrated optical components with high spatial resolution or microfluidic channels when combined with HF etching. The same fabrication technique can thus be employed to produce monolithic optofluidic devices for sensing applications. One of the most common sensing schemes involves evanescent optical interaction; therefore, the channel must meet some requirements regarding surface roughness, which will depend on the laser writing conditions, as described in this paper. However, of more significance is the distance between waveguiding medium and microfluidic channel that must be accurately defined. This control can be achieved by monitoring the etching reaction of a waveguide grating written a few microns from the channel, as introduced in this paper. In addition to its function as an etching monitor, the grating can also be used as a coarse refractive index sensor device.

2014

Advanced experiments with an Erbium doped fiber laser

Autores
Marques, PVS; Marques, MB; Rosa, CC;

Publicação
12TH EDUCATION AND TRAINING IN OPTICS AND PHOTONICS CONFERENCE

Abstract
This communication describes an optical hands-on fiber laser experiment aimed at advanced college courses. Optical amplifiers and laser sources represent very important optical devices in numerous applications ranging from telecommunications to medicine. The study of advanced photonics experiments is particularly relevant at undergraduate and master level. This paper discusses the implementation of an optical fiber laser made with a cavity built with two tunable Bragg gratings. This scheme allows the students to understand the laser working principles as a function of the laser cavity set-up. One or both of the gratings can be finely tuned in wavelength through applied stress; therefore, the degree of spectral mismatch of the two gratings can be adjusted, effectively changing the cavity feedback. The impact of the cavity conditions on the laser threshold, spectrum and efficiency is analyzed. This experiment assumes that in a previous practice, the students should had already characterized the erbium doped fiber in terms of absorption and fluorescent spectra, and the spectral gain as a function of pump power.

2015

Eight year experience in open ended instrumentation laboratory

Autores
Marques, MB; Rosa, CC; Marques, PVS;

Publicação
EDUCATION AND TRAINING IN OPTICS AND PHOTONICS: ETOP 2015

Abstract
When designing laboratory courses in a Physics Major we consider a range of objectives: teaching Physics; developing lab competencies; instrument control and data acquisition; learning about measurement errors and error propagation; an introduction to project management; team work skills and scientific writing. But nowadays we face pressure to decrease laboratory hours due to the cost involved. Many universities are replacing lab classes for simulation activities, hiring PhD. and master students to give first year lab classes, and reducing lab hours. This leads to formatted lab scripts and poor autonomy of the students, and failure to enhance creativity and autonomy. In this paper we present our eight year experience with a laboratory course that is mandatory in the third year of Physics and Physical Engineering degrees. Since the students had previously two standard laboratory courses, we focused on teaching instrumentation and giving students autonomy. The course is divided in two parts: one third is dedicated to learn computer controlled instrumentation and data acquisition (based in LabView); the final 2/3 is dedicated to a group project. In this project, the team (2 or 3 students) must develop a project and present it in a typical conference format at the end of the semester. The project assignments are usually not very detailed (about two or three lines long), giving only general guidelines pointing to a successful project (students often recycle objectives putting forward a very personal project); all of them require assembling some hardware. Due to our background, about one third of the projects are related to Optics.

2017

Fabrication of Microfluidic Channels by Femtosecond Laser Micromachining and Application in Optofluidics

Autores
Maia, JM; Amorim, VA; Alexandre, D; Marques, PVS;

Publicação
PROCEEDINGS OF THE 5TH INTERNATIONAL CONFERENCE ON PHOTONICS, OPTICS AND LASER TECHNOLOGY (PHOTOPTICS)

Abstract
Micromachining with femtosecond laser can be exploited to fabricate optical components and microfluidic channels in fused silica, due to internal modification of the glass properties that is induced by the laser beam. In this paper, we refer to the formation of microfluidic channels, where an optimization of the fabrication procedure was conducted by examining etch rate and surface roughness as a function of the irradiation conditions. Microfluidic channels with high and uniform aspect ratio and with smooth sidewalls were obtained, and such structures were successfully integrated with optical components. The obtained results set the foundations towards the development of new optofluidic devices.

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