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Dive into the research topics where A. Guerreiro is active.

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Featured researches published by A. Guerreiro.


international quantum electronics conference | 2007

Optomechanical entanglement between a movable mirror and a cavity field

David Vitali; Sylvain Gigan; Aires Ferreira; H. R. Böhm; Paolo Tombesi; A. Guerreiro; Vlatko Vedral; Anton Zeilinger; Markus Aspelmeyer

In this paper we propose an experimental scheme to create and probe optomechanical entanglement between a light field and a mechanical oscillator. This is achieved using a bright laser field that resonates inside a cavity and couples to the position and momentum of a moving (micro)mirror.


Applied Optics | 2007

Strain sensitivity control of fiber Bragg grating structures with fused tapers

Orlando Frazão; Susana O. Silva; A. Guerreiro; J. L. Santos; L. A. Ferreira; Francisco M. Araújo

We report on the analysis and experimental validation of the strain sensitivity dependences of a fiber Bragg grating written in standard optical fiber when combined with fused tapers. By controlling the difference between the cross sections of the fused taper and the Bragg grating, the strain sensitivity of the Bragg wavelength can be changed by acting on the gauge length. The strain sensing characteristics of an interferometric structure formed by fabricating a fused taper in the middle of a fiber Bragg grating are also reported.


Physical Review Letters | 2006

Macroscopic thermal entanglement due to radiation pressure.

Aires Ferreira; A. Guerreiro; Vlatko Vedral

Can entanglement and the quantum behavior in physical systems survive at arbitrary high temperatures? In this Letter we show that this is the case for a electromagnetic field mode in an optical cavity with a movable mirror in a thermal state. We also identify two different dynamical regimes of generation of entanglement separated by a critical coupling strength.


Journal of Lightwave Technology | 2015

New Trends on Optical Fiber Tweezers

Rita S. Rodrigues Ribeiro; Olivier Soppera; Abel Oliva; A. Guerreiro; P. A. S. Jorge

In the last few decades, optical trapping has played an unique role concerning contactless trapping and manipulation of biological specimens. More recently, optical fiber tweezers (OFTs) are emerging as a desirable alternative to bulk optical systems. In this paper, an overview of the state of the art of OFTs is presented, focusing on the main fabrication methods, their features and main achievements. In addition, new OFTs fabricated by guided wave photo polymerization are reported. Their theoretical and experimental characterization is given and results demonstrating its application in the manipulation of yeast cells and the organelles of plant cells are presented.


IEEE Sensors Journal | 2015

SPR Microstructured D-Type Optical Fiber Sensor Configuration for Refractive Index Measurement

D. F. Santos; A. Guerreiro; J. M. Baptista

This paper presents the performance analysis of a sensing configuration of refractive index, based on surface plasmon resonance (SPR) in microstructured D-type optical fiber with a thin gold layer, using the finite-element method. The configuration is analyzed in terms of the loss and distribution Poynting vector. The results are compared with a conventional SPR D-type optical fiber sensor for refractive index measurement. The simulation results show an improvement of the sensitivity and resolution (10 × 103 nm/RIU and 9.8 × 10-6 RIU, respectively, when considering an accurately spectral variation detection of 0.1 nm).


Laser and Particle Beams | 2001

X-ray emission from laser-irradiated gold targets with surface modulation

T. Desai; H. Daido; M. Suzuki; N. Sakaya; A. Guerreiro; Kunioki Mima

X-ray emission spectra in the 5-22 nm range were recorded from planar and structured (meshlike groove surface) gold targets at 45° and 90° to the laser axis. A laser beam of 10-ns duration with E L ≤ 700 mJ and 1.06-μm wavelength was used for the experiment. Experimental results indicate an enhanced X-ray yield from a structured target as compared to a planar target under identical experimental conditions. Increased X-ray emission is attributed to plasma confinement and the possibility of conversion of kinetic energy into localized thermal energy of the plasma. Results are analyzed explicitly on the incident laser energy.


Journal of Optics B-quantum and Semiclassical Optics | 2005

New mechanism of vacuum radiation from non-accelerated moving boundaries

A. Guerreiro; J. T. Mendonça; Ana Maria Gracioso Martins

We derive the effects of time refraction in a dispersive medium. A new type of radiation process is described that extends the concept of Unruh radiation to a non-accelerated but superluminal perturbation of the optical properties of a medium. The case of a plasma is considered as an example.


Scientific Reports | 2017

Fabrication of Fresnel plates on optical fibres by FIB milling for optical trapping, manipulation and detection of single cells

Rita S. Rodrigues Ribeiro; Pabitra Dahal; A. Guerreiro; P. A. S. Jorge; Jaime Viegas

The development of economical optical devices with a reduced footprint foreseeing manipulation, sorting and detection of single cells and other micro particles have been encouraged by cellular biology requirements. Nonetheless, researchers are still ambitious for advances in this field. This paper presents Fresnel zone and phase plates fabricated on mode expanded optical fibres for optical trapping. The diffractive structures were fabricated using focused ion beam milling. The zone plates presented in this work have focal distance of ~5 µm, while the focal distance of the phase plates is ~10 µm. The phase plates are implemented in an optical trapping configuration, and 2D manipulation and detection of 8 µm PMMA beads and yeast cells is reported. This enables new applications for optical trapping setups based on diffractive optical elements on optical fibre tips, where feedback systems can be integrated to automatically detect, manipulate and sort cells.


Optics Letters | 2016

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

Rita S. Rodrigues Ribeiro; Pabitra Dahal; A. Guerreiro; P. A. S. Jorge; Jaime Viegas

This Letter reports a new method for the generation of optical vortices using a micropatterned optical fiber tip. Here, a spiral phase plate (2π 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 (LG01), which carries orbital angular momentum. The experimental results are supported by computational simulations based on the finite-difference time-domain method.


Journal of Plasma Physics | 2007

Hamiltonian formulation of direct laser acceleration in vacuum

M. Eloy; A. Guerreiro; J. T. Mendonça; R. Bingham

We present a new formulation for the direct laser acceleration of electrons in vacuum based on the Hamiltonian theory. Two different regimes for the snow-plowed, accelerated electrons are identified and characterized, the first pertaining to high-intensity and the second to low-intensity pulses, both leading to efficient electron acceleration. Particle energy yields are shown to be independent of the exact shape of the laser pulse and energy gains are estimated.

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J. T. Mendonça

Instituto Superior Técnico

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João C. Costa

Instituto Superior de Engenharia de Lisboa

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