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Vakili A.,Northeastern University | Hollmann J.A.,Institute of Photonic science | Holt R.G.,Boston University | Dimarzio C.A.,Northeastern University
Progress in Biomedical Optics and Imaging - Proceedings of SPIE | Year: 2016

Optical imaging in a turbid medium is limited because of multiple scattering a photon undergoes while traveling through the medium. Therefore, optical imaging is unable to provide high resolution information deep in the medium. In the case of soft tissue, acoustic waves unlike light, can travel through the medium with negligible scattering. However, acoustic waves cannot provide medically relevant contrast as good as light. Hybrid solutions have been applied to use the benefits of both imaging methods. A focused acoustic wave generates a force inside an acoustically absorbing medium known as acoustic radiation force (ARF). ARF induces particle displacement within the medium. The amount of displacement is a function of mechanical properties of the medium and the applied force. To monitor the displacement induced by the ARF, speckle pattern analysis can be used. The speckle pattern is the result of interfering optical waves with different phases. As light travels through the medium, it undergoes several scattering events. Hence, it generates different scattering paths which depends on the location of the particles. Light waves that travel along these paths have different phases (different optical path lengths). ARF induces displacement to scatterers within the acoustic focal volume, and changes the optical path length. In addition, temperature rise due to conversion of absorbed acoustic energy to heat, changes the index of refraction and therefore, changes the optical path length of the scattering paths. The result is a change in the speckle pattern. Results suggest that the average change in the speckle pattern measures the displacement of particles and temperature rise within the acoustic wave focal area, hence can provide mechanical and thermal properties of the medium. © 2016 SPIE. Source

Afzelius M.,University of Geneva | Gisin N.,University of Geneva | De Riedmatten H.,Institute of Photonic science
Physics Today | Year: 2015

The quantum state of a photon can be transferred to a single trapped atom or to a bunch of atoms in a gas or solid, and is stored for later release on demand. Source

De Arquer F.P.G.,Institute of Photonic science | Volski V.,Catholic University of Leuven | Verellen N.,Catholic University of Leuven | Verellen N.,Institute for Nanoscale Physics and Chemistry | And 3 more authors.
IEEE Transactions on Antennas and Propagation | Year: 2011

An optical nano dipole antenna is analyzed by means of its input impedance as well as the matching properties of the antenna topology and material configuration. A comparison of this classical microwave driving method with plane wave excitation is accomplished, contrasting the resonances in the input impedance and optical cross sections for several setups, and analyzing the spectral response shape. It is found that for all structures analyzed, a simple linear expression can be defined characterizing the relation between total dipole length and resonant wavelength. The fact that this linear relationship remains valid for different excitation models, for most widely used antenna materials (Au, Ag, Cu, and Al) and even in the presence of substrates is important with respect to practical designs. To our knowledge, such an extensive study has not been performed before. © 2006 IEEE. Source

Buret M.,Laboratory Interdisciplinaire Carnot de Bourgogne | Uskov A.V.,RAS Lebedev Physical Institute | Dellinger J.,Laboratory Interdisciplinaire Carnot de Bourgogne | Dellinger J.,CNRS Computer Science and Engineering Laboratory | And 8 more authors.
Nano Letters | Year: 2015

Nanoscale electronics and photonics are among the most promising research areas providing functional nanocomponents for data transfer and signal processing. By adopting metal-based optical antennas as a disruptive technological vehicle, we demonstrate that these two device-generating technologies can be interfaced to create an electronically driven self-emitting unit. This nanoscale plasmonic transmitter operates by injecting electrons in a contacted tunneling antenna feedgap. Under certain operating conditions, we show that the antenna enters a highly nonlinear regime in which the energy of the emitted photons exceeds the quantum limit imposed by the applied bias. We propose a model based upon the spontaneous emission of hot electrons that correctly reproduces the experimental findings. The electron-fed optical antennas described here are critical devices for interfacing electrons and photons, enabling thus the development of optical transceivers for on-chip wireless broadcasting of information at the nanoscale. © 2015 American Chemical Society. Source

Vilella E.,University of Barcelona | Vilella E.,University of Liverpool | Garcia J.,University of Barcelona | Garcia J.,Institute of Photonic science | And 2 more authors.
IEEE Sensors Journal | Year: 2016

The extraordinary sensitivity of single-photon avalanche diodes (SPADs) makes these devices the ideal option for vision systems aimed at low-light applications. Nevertheless, there exist large dark count rate and photon detection probability non-uniformities, which reduce the dynamic range of the detector. As a result, the capability to create image contrast is severely damaged or even lost. This paper presents the implementation of a correction algorithm to compensate for the mentioned non-uniformities and thus extend the contrast of the generated images. To demonstrate its efficiency, the proposed technique is applied to real images obtained with a fabricated SPAD image sensor. An increase of more than 3 b of contrast is obtained. © 2015 IEEE. Source

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