Institute of Photonic science

Barcelona, Spain

Institute of Photonic science

Barcelona, Spain
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Vakili A.,Northeastern University | Hollmann J.L.,Institute of Photonic science | Holt R.G.,Boston University | Dimarzio C.A.,Northeastern University
Progress in Biomedical Optics and Imaging - Proceedings of SPIE | Year: 2017

Optical imaging modalities are proved to be able to provide images with resolution required to image subcellular particles, however, imaging depth of optical imaging modalities are limited due to strong absorption and scattering. In contrast, ultrasound imaging modalities can provide images deeper in the tissue due to negligible scattering in tissue, but they suffer from poor resolution and contrast. Hybrid imaging modalities such as ultrasound modulated optical tomography (UOT) utilize advantages of both optical and ultrasound imaging modalities. UOT utilizes pressure waves to modulate light with ultrasound frequency that results in a week signal that requires expensive detection equipment. In Contrast, we propose to use acoustic radiation force (ARF) to tag the light that travels through the ultrasound focal spot and generate a stronger signal. Monitoring the changes in the speckle pattern reflects both mechanical and thermal properties of the medium. In this paper we have utilized our model with fixed-particle Monte Carlo to simulate the mean irradiance change (MIC) signal variations due to particle displacement and temperature rise. Results suggest that neglecting the temperature rise for short ultrasound exposure times, the change in the MIC signal reflects the local stiffness of the medium at the ultrasound focal spot and can be utilized to generate the stiffness image of the medium. © 2017 SPIE.

Agency: GTR | Branch: EPSRC | Program: | Phase: Research Grant | Award Amount: 84.72K | Year: 2013

Nanoscale quantum optics is a promising new field aimed at coherent control and manipulation of single photons emitted by individual quantum emitters in a nanostructured photonic environment. Single emitters have dimensions much smaller than the wavelength of light, and therefore interact slowly and omni-directionally with radiation, placing limits on photon absorption and emission. These intrinsic fluorescence limits can be overcome when the source is placed in a nanostructured photonic material. Multi-scale (fractal) structures are a new class of particularly interesting photonic materials, since they lead to spatial localisation of the electromagnetic energy into subwavelength areas (hot spots of 10s of nm) over a wide spectral range, which are driven by optical excitations coupled to the network on different scales. Here I propose to investigate collective plasmonic systems, based on plasmon multiple scattering and interference on metallic networks. I will study natural gold networks and artificially designed one. I will approach these structures using a network theory approach, a statistical method centred on the network topology, made of links and nodes. This method has the potentiality of describing the complex system with few robust parameters, extracted from the rich microscopic details, and thus provides much deeper understanding. The study of network optical properties will focus on probing one of the most robust modal properties: the local density of optical states. This is a key fundamental quantity involved in light-matter interaction, as it provides a direct measure for the probability of spontaneous light emission (the Purcell effect), light absorption and scattering. I propose to identify the emergent nature of the different optical modes of complex plasmonic networks by studying the statistics of the LDOS in artificial plasmonic networks. I plan to understand the inner character of the complex plasmonic modes, and to reveal subwavelength hot-spots, critically localized states and chaotic mode signatures. This knowledge will be exploited to design and engineer the LDOS for local fluorescence enhancement and to exploit the network as an unconventional antenna to control the fluorescence of an individual colloidal quantum dot, enhance its radiation rate, boost and manipulate its directionality. I will aim at demonstrating a strong link between the plasmonic network structures, their optical properties and their effect on a light emitter.

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.

Resan B.,Time-Bandwidth Products | Aviles-Espinosa R.,Institute of Photonic science | Kurmulis S.,Time-Bandwidth Products | Licea-Rodriguez J.,CICESE | And 5 more authors.
Optics Express | Year: 2014

We developed a low-cost, low-noise, tunable, high-peak-power, ultrafast laser system based on a SESAM-modelocked, solid-state Yb tungstate laser plus spectral broadening via a microstructured fiber followed by pulse compression. The spectral selection, tuning, and pulse compression are performed with a simple prism compressor. The output pulses are tunable from 800 to 1250 nm, with the pulse duration down to 25 fs, and average output power up to 150 mW, at 80 MHz pulse repetition rate. We introduce the figure of merit (FOM) for the two-photon and multi-photon imaging (or other nonlinear processes), which is a useful guideline in discussions and for designing the lasers for an improved microscopy signal. Using a 40 MHz pulse repetition rate laser system, with twice lower FOM, we obtained high signal-to-noise ratio two-photon fluorescence images with or without averaging, of mouse intestine section and zebra fish embryo. The obtained images demonstrate that the developed system is capable of nonlinear (TPE, SHG) imaging in a multimodal operation. The system could be potentially used in a variety of other techniques including, THG, CARS and applications such as nanosurgery. © 2014 Optical Society of America.

Nieder J.B.,Free University of Berlin | Nieder J.B.,Institute of Photonic science | Stojkovic E.A.,University of Chicago | Stojkovic E.A.,Northeastern Illinois University | And 5 more authors.
Journal of Physical Chemistry B | Year: 2013

Fluorescence line narrowing (FLN) spectroscopy was used to study bacteriophytochromes and variants from various species in their red-absorbing Pr ground state, including phytochromes Agp1 from Agrobacterium tumefaciens, DrBphP from Deinococcus radiodurans, and RpBphP2 and RpBphP3 from Rhodopseudomonas palustris. A species-dependent narrowing of the fluorescence emission bands is observed. The results suggest varied pigment-protein interactions, possibly connected to chromophore mobility or extended water pyrrole networks inside of the differing binding pockets. Solvent water isotope exchange from H2O-based buffer to D2O-based buffer solutions was used to identify specific vibrational modes of the chromophore. In addition to the expected frequency shifts upon isotope exchange, the line narrowing efficiency is increased in deuterated compared to protonated surroundings. We conclude that proton dynamics inside of the protein binding pocket are a dominant source of spectral diffusion at low temperatures, which possibly relates to the previous observation that the electronic transition is directly coupled to proton transfer. The FLN spectra of Agp1 reconstituted with a synthesized pigment shows strong line narrowing efficiency even in protonated buffer solution. The FLN spectra of a point mutant of RpBphP3 highlight the involvement of aspartate 216 in a hydrogen bond network around the chromophore. On the basis of similar FLN characteristics in RpBphP2 and RpBphP3, we propose a similarly extended hydrogen bond network around their chromophores despite the different photoreactions leading to red- or blue-shifted absorption relative to the respective photoreceptors' ground-state absorption. © 2013 American Chemical Society.

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.

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.

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.

PubMed | McGill University and Institute of Photonic science
Type: | Journal: TheScientificWorldJournal | Year: 2014

We provide a comprehensive picture of magnetotransport in graphene monolayers in the limit of nonquantizing magnetic fields. We discuss the effects of two-carrier transport, weak localization, weak antilocalization, and strong localization for graphene devices of various mobilities, through theory, experiments, and numerical simulations. In particular, we observe a minimum in the weak localization and strong localization length reminiscent of the minimum in the conductivity, which allows us to make the connection between weak and strong localization. This provides a unified framework for both localizations, which explains the observed experimental features. We compare these results to numerical simulation and find a remarkable agreement between theory, experiment, and numerics. Various graphene devices were used in this study, including graphene on different substrates, such as glass and silicon, as well as low and high mobility devices.

PubMed | TU Munich, Stanford University and Institute of Photonic science
Type: | Journal: eLife | Year: 2017

Our bodies are in constant motion and so are the neurons that invade each tissue. Motion-induced neuron deformation and damage are associated with several neurodegenerative conditions. Here, we investigated the question of how the neuronal cytoskeleton protects axons and dendrites from mechanical stress, exploiting mutations in UNC-70 -spectrin, PTL-1 tau/MAP2-like and MEC-7 -tubulin proteins in

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