351 results match your criteria Ottica Italiana Italian Optics [Journal]


Polarization-dependent deformation in light responsive polymers doped by dichroic dyes.

Soft Matter 2018 Dec 4. Epub 2018 Dec 4.

European Laboratory for Non-Linear Spectroscopy (LENS), University of Florence, via Nello Carrara 1, 50019 Sesto Fiorentino, Italy. and Department of Chemistry "Ugo Schiff", University of Florence, via della Lastruccia 3-13, 50019 Sesto Fiorentino, Italy and Istituto Nazionale di Ricerca Metrologica INRiM, Strada delle Cacce 91, 10135 Turin, Italy.

Light represents a very versatile stimulus and its use to control the deformation in shape-changing polymers can take advantage of multiple parameters (such as wavelength, intensity and polarization) to be explored in order to obtain differentiated responses. Polymers with selected color responsiveness are commonly prepared by using different dyes, while a polarization-dependent control can be introduced exploiting trans-cis isomerization of azobenzenes. As shape-changing polymers driven by a photothermal effect are gaining more and more attention in many application fields, exploring polarization to modulate their response could enlarge the tuning parameter space and provide an insight into the material optical properties. Read More

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December 2018
3 Reads

Polymeric nanoparticles promote endocytosis of a survivin molecular beacon: Localization and fate of nanoparticles and beacon in human A549 cells.

Life Sci 2018 Dec 7;215:106-112. Epub 2018 Nov 7.

Istituto di Fisica Applicata "Nello Carrara", Consiglio Nazionale delle Ricerche, Via Madonna del Piano 10, 50019 Sesto Fiorentino, FI, Italy. Electronic address:

Polymethylmethacrylate core-shell fluorescent nanoparticles promote, in human lung A549 cancer cells, the internalization of a molecular beacon (MB) specific for survivin mRNA, an anti-apoptotic protein overexpressed in cancer cells.

Aims: To design an effective drug delivery system, the knowledge of the uptake mechanism and of the nanoparticles (NPs) and MB fate is required.

Materials And Methods And Key Findings: Experiments with dextran as marker for endocytosis showed that in the presence of NPs the number of endocytic vesicles per cell doubled and their mean size significantly (p < 0. Read More

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December 2018
4 Reads

Geometrical Bounds on Irreversibility in Open Quantum Systems.

Phys Rev Lett 2018 Oct;121(16):160602

Dipartimento di Scienze, Università degli Studi Roma Tre, Via della Vasca Navale 84, 00146, Rome, Italy.

The Clausius inequality has deep implications for reversibility and the arrow of time. Quantum theory is able to extend this result for closed systems by inspecting the trajectory of the density matrix on its manifold. Here we show that this approach can provide an upper and lower bound to the irreversible entropy production for open quantum systems as well. Read More

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October 2018
1 Read

Anvil-profiled penetrating keratoplasty: load resistance evaluation.

Biomech Model Mechanobiol 2018 Oct 31. Epub 2018 Oct 31.

Istituto Nazionale di Ottica, Consiglio Nazionale delle Ricerche, Via G. Moruzzi 1, 56124, Pisa, Italy.

The aim of this study was to qualitatively evaluate the biomechanical load resistance of different surgical wound configurations (mushroom, zig-zag, anvil and conventional trephination) in penetrating keratoplasty (PK) by designing a 2D and a 3D finite-element biomechanical model of the cornea. A mathematical model of the human cornea was developed, and different geometric configurations for PK were designed. The internal pressure was raised until the wound misaligned; wound prolapse then occurred. Read More

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October 2018
3 Reads

Multianalytical non-invasive characterization of phthalocyanine acrylic paints through spectroscopic and non-linear optical techniques.

Spectrochim Acta A Mol Biomol Spectrosc 2019 Feb 22;208:262-270. Epub 2018 Sep 22.

Consiglio Nazionale delle Ricerche - Istituto Nazionale di Ottica, CNR-INO, Largo Enrico Fermi 6, 50125 Firenze, Italy.

The documentation and monitoring of cleaning operations on paintings benefit from the identification and determination of thickness of the materials to be selectively removed. Since in artworks diagnosis the preservation of the object's integrity is a priority, the application of non-invasive techniques is commonly preferred. In this work, we present the results obtained with a set of non-invasive optical techniques for the chemical and physical characterization of six copper-phthalocyanine (Cu-Pc) acrylic paints. Read More

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February 2019

Solution and Solid-State Emission Toggling of a Photochromic Hydrazone.

J Am Chem Soc 2018 Oct 25;140(39):12323-12327. Epub 2018 Sep 25.

Department of Chemistry , Dartmouth College , Hanover , New Hampshire 03755 , United States.

The proliferation of light-activated switches in recent years has enabled their use in a broad range of applications encompassing an array of research fields and disciplines. All current systems, however, have limitations (e.g. Read More

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October 2018
1 Read

Modulation Instability Induced Frequency Comb Generation in a Continuously Pumped Optical Parametric Oscillator.

Phys Rev Lett 2018 Aug;121(9):093903

CNR-INO, Istituto Nazionale di Ottica, Via Campi Flegrei 34, I-80078 Pozzuoli (NA), Italy.

Continuously pumped passive nonlinear cavities can be harnessed for the creation of novel optical frequency combs. While most research has focused on third-order "Kerr" nonlinear interactions, recent studies have shown that frequency comb formation can also occur via second-order nonlinear effects. Here, we report on the formation of quadratic combs in optical parametric oscillator (OPO) configurations. Read More

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Cold-Adaptation Signatures in the Ligand Rebinding Kinetics to the Truncated Hemoglobin of the Antarctic Bacterium Pseudoalteromonas haloplanktis TAC125.

J Phys Chem B 2018 Oct 3. Epub 2018 Oct 3.

Dipartimento di Scienze Matematiche, Fisiche e Informatiche , Università di Parma , Parco Area delle Scienze 7A , 43124 , Parma , Italy.

Cold-adapted organisms have evolved proteins endowed with higher flexibility and lower stability in comparison to their thermophilic homologues, resulting in enhanced reaction rates at low temperatures. In this context, protein-bound water molecules were suggested to play a major role, and their weaker interactions at protein active sites have been associated with cold adaptation. In this work, we tested this hypothesis on truncated hemoglobins (a family of microbial heme-proteins of yet-unclear function) applying molecular dynamics simulations and ligand-rebinding kinetics on a protein from the Antarctic bacterium Pseudoalteromonas haloplanktis TAC125 in comparison with its thermophilic Thermobifida fusca homologue. Read More

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October 2018
2 Reads

SiCILIA-Silicon Carbide Detectors for Intense Luminosity Investigations and Applications.

Sensors (Basel) 2018 Jul 15;18(7). Epub 2018 Jul 15.

Institute for Microelectronics and Microsystems (IMM), National Research Council (CNR), VIII Strada, 5, 95121 Catania, Italy.

Silicon carbide (SiC) is a compound semiconductor, which is considered as a possible alternative to silicon for particles and photons detection. Its characteristics make it very promising for the next generation of nuclear and particle physics experiments at high beam luminosity. Silicon Carbide detectors for Intense Luminosity Investigations and Applications (SiCILIA) is a project starting as a collaboration between the Italian National Institute of Nuclear Physics (INFN) and IMM-CNR, aiming at the realization of innovative detection systems based on SiC. Read More

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July 2018
13 Reads

A New Precision Spectroscopy Based Method for Boltzmann Constant Determination and Primary Thermometry.

J Phys Chem A 2018 Jul 10;122(28):6026-6030. Epub 2018 Jul 10.

CNR-INO , Istituto Nazionale di Ottica , Largo E. Fermi 6 , 50125 Firenze , Italy.

We propose a new independent thermometry method, line strength ratio thermometry (LRT), based on optical spectroscopy measurement of the line strength intensity ratio R between pairs of molecular transitions. Due to strong dependence of R on kT, a given measurement uncertainty δR for R reflects in a small uncertainty of kT determination. By assuming experimental uncertainties of R and T to be those reported in literature, we foresee a k determination at the 5 ppm level, which is better than the most precise k determination by using Doppler broadening thermometry (DBT). Read More

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July 2018
23 Reads

Self-Bound Quantum Droplets of Atomic Mixtures in Free Space.

Phys Rev Lett 2018 Jun;120(23):235301

LENS and Dipartimento di Fisica e Astronomia, Università di Firenze, 50019 Sesto Fiorentino, Italy.

Self-bound quantum droplets are a newly discovered phase in the context of ultracold atoms. In this Letter, we report their experimental realization following the original proposal by Petrov [Phys. Rev. Read More

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Functional Multichannel Poly(Propylene Fumarate)-Collagen Scaffold with Collagen-Binding Neurotrophic Factor 3 Promotes Neural Regeneration After Transected Spinal Cord Injury.

Adv Healthc Mater 2018 Jul 19;7(14):e1800315. Epub 2018 Jun 19.

Institute of Combined Injury, State Key Laboratory of Trauma, Burns and Combined Injury, Chongqing Engineering Research Center for Nanomedicine, Chongqing Engineering Research Center for Biomaterials and Regenerative Medicine, College of Preventive Medicine, Army Medical University (Third Military Medical University), 30th Gaotanyan street, Chongqing, 400038, China.

Many factors contribute to the poor axonal regrowth and ineffective functional recovery after spinal cord injury (SCI). Biomaterials have been used for SCI repair by promoting bridge formation and reconnecting the neural tissue at the lesion site. The mechanical properties of biomaterials are critical for successful design to ensure the stable support as soon as possible when compressed by the surrounding spine and musculature. Read More

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July 2018
10 Reads

Vortex lattice in the crossover of a Bose gas from weak coupling to unitarity.

Sci Rep 2018 Jun 11;8(1):8825. Epub 2018 Jun 11.

Dipartimento di Fisica e Astronomia "Galileo Galilei", Università di Padova, Via Marzolo 8, 35131, Padova, Italy.

The formation of a regular lattice of quantized vortices in a fluid under rotation is a smoking-gun signature of its superfluid nature. Here we study the vortex lattice in a dilute superfluid gas of bosonic atoms at zero temperature along the crossover from the weak-coupling regime, where the inter-atomic scattering length is very small compared to the average distance between atoms, to the unitarity regime, where the inter-atomic scattering length diverges. This study is based on high-performance numerical simulations of the time-dependent nonlinear Schrödinger equation for the superfluid order parameter in three spatial dimensions, using a realistic analytical expression for the bulk equation of state of the system along the crossover from weak-coupling to unitarity. Read More

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Self-Induced Faraday Instability Laser.

Phys Rev Lett 2018 May;120(21):213902

Novosibirsk State University, 1 Pirogova str., Novosibirsk 630090, Russia.

We predict the onset of self-induced parametric or Faraday instabilities in a laser, spontaneously caused by the presence of pump depletion, which leads to a periodic gain landscape for light propagating in the cavity. As a result of the instability, continuous wave oscillation becomes unstable even in the normal dispersion regime of the cavity, and a periodic train of pulses with ultrahigh repetition rate is generated. Application to the case of Raman fiber lasers is described, in good quantitative agreement between our conceptual analysis and numerical modeling. Read More

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Solvent Effects on the Actinic Step of Donor-Acceptor Stenhouse Adduct Photoswitching.

Angew Chem Int Ed Engl 2018 Jul 30;57(27):8063-8068. Epub 2018 May 30.

Centre for Systems Chemistry, Stratingh Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands.

Donor-acceptor Stenhouse adducts (DASAs) are negative photochromes that switch with visible light and are highly promising for applications ranging from smart materials to biological systems. However, the strong solvent dependence of the photoswitching kinetics limits their application. The nature of the photoswitching mechanism in different solvents is key for addressing the solvatochromism of DASAs, but as yet has remained elusive. Read More

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July 2018
16 Reads

Cortical BOLD responses to moderate- and high-speed motion in the human visual cortex.

Sci Rep 2018 May 29;8(1):8357. Epub 2018 May 29.

Department of Translational Research on New Technologies in Medicine and Surgery, University of Pisa, Pisa, Italy.

We investigated the BOLD response of visual cortical and sub-cortical regions to fast drifting motion presented over wide fields, including the far periphery. Stimuli were sinusoidal gratings of 50% contrast moving at moderate and very high speeds (38 and 570 °/s), projected to a large field of view (~60°). Both stimuli generated strong and balanced responses in the lateral geniculate nucleus and the superior colliculus. Read More

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May 2018
1 Read

A Comprehensive Characterization of a 10 at.% Yb:YSAG Laser Ceramic Sample.

Materials (Basel) 2018 May 18;11(5). Epub 2018 May 18.

Istituto Nazionale di Ottica, INO, Consiglio Nazionale delle Ricerche, CNR, Via Madonna del Piano 10C, 50019 Sesto Fiorentino (Fi), Italy.

We report a comprehensive characterization of a 10 at.% Yb-doped YSAG (Yb:Y₃ScAlO, x = 1.5) ceramic, including microstructural, spectroscopic and laser properties. Read More

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May 2018
13 Reads

Evidence of a Critical Phase Transition in Purely Temporal Dynamics with Long-Delayed Feedback.

Phys Rev Lett 2018 Apr;120(17):173901

Consiglio Nazionale delle Ricerche, Istituto dei Sistemi Complessi, Via Madonna del Piano 10, 50019 Sesto Fiorentino, Italy.

Experimental evidence of an absorbing phase transition, so far associated with spatiotemporal dynamics, is provided in a purely temporal optical system. A bistable semiconductor laser, with long-delayed optoelectronic feedback and multiplicative noise, shows the peculiar features of a critical phenomenon belonging to the directed percolation universality class. The numerical study of a simple, effective model provides accurate estimates of the transition critical exponents, in agreement with both theory and our experiment. Read More

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Reply to "Comment on 'Behavior of Supercritical Fluids across the Frenkel Line'".

J Phys Chem B 2018 Jun 21;122(22):6120-6123. Epub 2018 May 21.

Center for Life Nano Science @Sapienza , Istituto Italiano di Tecnologia , 295 Viale Regina Elena , I-00161 Roma , Italy.

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Photochemical Control of Exciton Superradiance in Light-Harvesting Nanotubes.

ACS Nano 2018 May 3;12(5):4556-4564. Epub 2018 May 3.

Department of Chemistry and Biochemistry , University of California, Los Angeles , Los Angeles , California 90095 , United States.

Photosynthetic antennae and organic electronic materials use topological, structural, and molecular control of delocalized excitons to enhance and direct energy transfer. Interactions between the transition dipoles of individual chromophore units allow for coherent delocalization across multiple molecular sites. This delocalization, for specific geometries, greatly enhances the transition dipole moment of the lowest energy excitonic state relative to the chromophore and increases its radiative rate, a phenomenon known as superradiance. Read More

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May 2018
6 Reads

Self-Assembled Nanocrystals of Polycyclic Aromatic Hydrocarbons Show Photostable Single-Photon Emission.

ACS Nano 2018 May 12;12(5):4295-4303. Epub 2018 Apr 12.

CNR-INO , Istituto Nazionale di Ottica , Via Carrara 1 , 50019 Sesto F.no, Firenze , Italy.

Quantum technologies could largely benefit from the control of quantum emitters in sub-micrometric size crystals. These are naturally prone to integration in hybrid devices, including heterostructures and complex photonic devices. Currently available quantum emitters in nanocrystals suffer from spectral instability, preventing their use as single-photon sources for most quantum optics operations. Read More

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May 2018
1 Read

Imaging Optical Frequencies with 100  μHz Precision and 1.1  μm Resolution.

Phys Rev Lett 2018 Mar;120(10):103201

JILA, National Institute of Standards and Technology and University of Colorado, 440 UCB, Boulder, Colorado 80309, USA.

We implement imaging spectroscopy of the optical clock transition of lattice-trapped degenerate fermionic Sr in the Mott-insulating regime, combining micron spatial resolution with submillihertz spectral precision. We use these tools to demonstrate atomic coherence for up to 15 s on the clock transition and reach a record frequency precision of 2.5×10^{-19}. Read More

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March 2018
1 Read

Multiplexed direct-frequency-comb Vernier spectroscopy of carbon dioxide 2ν + ν ro-vibrational combination band.

J Chem Phys 2018 Mar;148(11):114303

Istituto Nazionale di Ottica-CNR, Dipartimento di Fisica-Università degli Studi di Firenze and European Laboratory for Non-linear Spectroscopy, Via N. Carrara 1, Sesto Fiorentino, Italy.

We investigated a set of nineteen CO transitions of the 2ν + ν ro-vibrational band in the spectral region from 5064 to 5126 cm at different pressures, using frequency-comb Vernier spectroscopy. Our spectrometer enabled the systematic acquisition of molecular absorption profiles with high precision. Spectroscopic parameters, namely, transition frequency, linestrength, and self-pressure broadening coefficient, have been accurately determined by using a global fit procedure. Read More

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Stimulated Brillouin Cavity Optomechanics in Liquid Droplets.

Phys Rev Lett 2018 Feb;120(7):073902

Consiglio Nazionale delle Ricerche, Istituto Nazionale di Ottica (INO), via Campi Flegrei, 34-Comprensorio A. Olivetti, 80078 Pozzuoli (Naples), Italy.

Liquid droplets are ubiquitous in nature wherein surface tension shapes them into perfect spheres with atomic-scale smooth surfaces. Here, we use stable droplets that cohost equatorial acoustical and optical resonances phase matched to enable the exchange of energy and momentum between sound and light. Relying on free-space laser excitation of multiple whispering-gallery modes, we harness a triple-resonant forward Brillouin scattering to stimulate optomechanical surface waves. Read More

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February 2018

Connecting Dissipation and Phase Slips in a Josephson Junction between Fermionic Superfluids.

Phys Rev Lett 2018 Jan;120(2):025302

Istituto Nazionale di Ottica del Consiglio Nazionale delle Ricerche (INO-CNR), 50019 Sesto Fiorentino, Italy.

We study the emergence of dissipation in an atomic Josephson junction between weakly coupled superfluid Fermi gases. We find that vortex-induced phase slippage is the dominant microscopic source of dissipation across the Bose-Einstein condensate-Bardeen-Cooper-Schrieffer crossover. We explore different dynamical regimes by tuning the bias chemical potential between the two superfluid reservoirs. Read More

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January 2018

Generalized Fano lineshapes reveal exceptional points in photonic molecules.

Nat Commun 2018 01 26;9(1):396. Epub 2018 Jan 26.

Department of Physics, University of Florence, via Sansone 1, 50019, Sesto Fiorentino, FI, Italy.

The optical behavior of coupled systems, in which the breaking of parity and time-reversal symmetry occurs, is drawing increasing attention to address the physics of the exceptional point singularity, i.e., when the real and imaginary parts of the normal-mode eigenfrequencies coincide. Read More

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January 2018
2 Reads

Λ-enhanced grey molasses on the D transition of Rubidium-87 atoms.

Sci Rep 2018 01 22;8(1):1301. Epub 2018 Jan 22.

LENS European Laboratory for Non-Linear Spectroscopy, and Dipartimento di Fisica e Astronomia, Università di Firenze, Sesto Fiorentino, 50019, Italy.

Laser cooling based on dark states, i.e. states decoupled from light, has proven to be effective to increase the phase-space density of cold trapped atoms. Read More

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January 2018
2 Reads

Radiation-pressure-driven ion Weibel instability and collisionless shocks.

Phys Rev E 2017 Sep 25;96(3-1):033204. Epub 2017 Sep 25.

LULI, Sorbonne Université, CNRS, Ecole Polytechnique, CEA, Université Paris-Saclay, Paris, France.

The Weibel instability from counterstreaming plasma flows is a basic process highly relevant for collisionless shock formation in astrophysics. In this paper we investigate, via two- and three-dimensional simulations, suitable configurations for laboratory investigations of the ion Weibel instability (IWI) driven by a fast quasineutral plasma flow launched into the target via the radiation pressure of an ultra-high-intensity laser pulse ("hole-boring" process). The use of S-polarized light at oblique incidence is found to be an optimal configuration for driving IWI, as it prevents the development of surface rippling observed at normal incidence that would lead to strong electron heating and would favor competing instabilities. Read More

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September 2017
1 Read

Tailoring Correlations of the Local Density of States in Disordered Photonic Materials.

Phys Rev Lett 2017 Jul 25;119(4):043902. Epub 2017 Jul 25.

Université Grenoble Alpes, LPMMC, F-38000 Grenoble, France.

We present experimental evidence for the different mechanisms driving the fluctuations of the local density of states (LDOS) in disordered photonic systems. We establish a clear link between the microscopic structure of the material and the frequency correlation function of LDOS accessed by a near-field hyperspectral imaging technique. We show, in particular, that short- and long-range frequency correlations of LDOS are controlled by different physical processes (multiple or single scattering processes, respectively) that can be-to some extent-manipulated independently. Read More

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Conditional Hybrid Nonclassicality.

Phys Rev Lett 2017 Sep 21;119(12):120403. Epub 2017 Sep 21.

AG Theoretische Quantenoptik, Institut für Physik, Universität Rostock, D-18051 Rostock, Germany.

We derive and implement a general method to characterize the nonclassicality in compound discrete- and continuous-variable systems. For this purpose, we introduce the operational notion of conditional hybrid nonclassicality which relates to the ability to produce a nonclassical continuous-variable state by projecting onto a general superposition of discrete-variable subsystem. We discuss the importance of this form of quantumness in connection with interfaces for quantum communication. Read More

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September 2017

Synthesis and Raman spectroscopy of a layered SiS phase at high pressures.

J Chem Phys 2018 Jan;148(1):014503

Istituto Nazionale di Ottica (CNR-INO) and European Laboratory for non Linear Spectroscopy (LENS), Via N. Carrara 1, 50019 Sesto Fiorentino, Italy.

Dichalcogenides are known to exhibit layered solid phases, at ambient and high pressures, where 2D layers of chemically bonded formula units are held together by van der Waals forces. These materials are of great interest for solid-state sciences and technology, along with other 2D systems such as graphene and phosphorene. SiS is an archetypal model system of the most fundamental interest within this ensemble. Read More

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January 2018
15 Reads

Diffraction-Limited Plenoptic Imaging with Correlated Light.

Phys Rev Lett 2017 Dec 15;119(24):243602. Epub 2017 Dec 15.

INFN, Sezione di Bari, I-70126 Bari, Italy.

Traditional optical imaging faces an unavoidable trade-off between resolution and depth of field (DOF). To increase resolution, high numerical apertures (NAs) are needed, but the associated large angular uncertainty results in a limited range of depths that can be put in sharp focus. Plenoptic imaging was introduced a few years ago to remedy this trade-off. Read More

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December 2017
5 Reads

Tailoring Photoisomerization Pathways in Donor-Acceptor Stenhouse Adducts: The Role of the Hydroxy Group.

J Phys Chem A 2018 Feb 18;122(4):955-964. Epub 2018 Jan 18.

Centre for Systems Chemistry, Stratingh Institute for Chemistry, University of Groningen , Nijenborgh 4, 9747 AG Groningen, The Netherlands.

Donor-acceptor Stenhouse adducts (DASAs) are a rapidly emerging class of visible light-activatable negative photochromes. They are closely related to (mero)cyanine dyes with the sole difference being a hydroxy group in the polyene chain. The presence or absence of the hydroxy group has far-reaching consequences for the photochemistry of the compound: cyanine dyes are widely used as fluorescent probes, whereas DASAs hold great promise for visible light-triggered photoswitching. Read More

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February 2018
37 Reads

Identification of minimal parameters for optimal suppression of chaos in dissipative driven systems.

Sci Rep 2017 Dec 21;7(1):17988. Epub 2017 Dec 21.

Departamento de Física Aplicada, E.I.I., Universidad de Extremadura, Apartado Postal 382, E-06006, Badajoz, Spain.

Taming chaos arising from dissipative non-autonomous nonlinear systems by applying additional harmonic excitations is a reliable and widely used procedure nowadays. But the suppressory effectiveness of generic non-harmonic periodic excitations continues to be a significant challenge both to our theoretical understanding and in practical applications. Here we show how the effectiveness of generic suppressory excitations is optimally enhanced when the impulse transmitted by them (time integral over two consecutive zeros) is judiciously controlled in a not obvious way. Read More

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December 2017
6 Reads

Localized solutions of Lugiato-Lefever equations with focused pump.

Sci Rep 2017 Dec 4;7(1):16876. Epub 2017 Dec 4.

Department of Physical Electronics, School of Electrical Engineering, Faculty of Engineering, Tel Aviv University, Tel Aviv, 69978, Israel.

Lugiato-Lefever (LL) equations in one and two dimensions (1D and 2D) accurately describe the dynamics of optical fields in pumped lossy cavities with the intrinsic Kerr nonlinearity. The external pump is usually assumed to be uniform, but it can be made tightly focused too-in particular, for building small pixels. We obtain solutions of the LL equations, with both the focusing and defocusing intrinsic nonlinearity, for 1D and 2D confined modes supported by the localized pump. Read More

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December 2017
4 Reads

Pseudo-spatial coherence resonance in an excitable laser with long delayed feedback.

Chaos 2017 Nov;27(11):114302

CNR - Istituto dei Sistemi Complessi, via Madonna del Piano 10, I-50019 Sesto Fiorentino, Italy.

The effect of noise in an excitable semiconductor laser with feedback is studied in the framework of the spatio-temporal representation of long delayed systems. Propagation, noise-induced creation, and destruction of excitable pulses in the pseudo time are observed. The addition of a variable quantity of noise leads to the occurrence of a phenomenon that we term "pseudo-spatial coherence resonance. Read More

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November 2017

Axion dark matter detection by laser induced fluorescence in rare-earth doped materials.

Sci Rep 2017 Nov 9;7(1):15168. Epub 2017 Nov 9.

Dip. di Fisica and INFN, Largo Bruno Pontecorvo, 3, I-56127, Pisa, Italy.

We present a detection scheme to search for QCD axion dark matter, that is based on a direct interaction between axions and electrons explicitly predicted by DFSZ axion models. The local axion dark matter field shall drive transitions between Zeeman-split atomic levels separated by the axion rest mass energy m c . Axion-related excitations are then detected with an upconversion scheme involving a pump laser that converts the absorbed axion energy (~hundreds of μeV) to visible or infrared photons, where single photon detection is an established technique. Read More

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November 2017
3 Reads

Quantum phase slips: from condensed matter to ultracold quantum gases.

Philos Trans A Math Phys Eng Sci 2017 Dec;375(2108)

Istituto Nazionale di Ottica, CNR, 50019 Sesto Fiorentino, Italy.

Quantum phase slips (QPS) are the primary excitations in one-dimensional superfluids and superconductors at low temperatures. They have been well characterized in most condensed-matter systems, and signatures of their existence have been recently observed in superfluids based on quantum gases too. In this review, we briefly summarize the main results obtained on the investigation of phase slips from superconductors to quantum gases. Read More

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December 2017

Equation of state and self-bound droplet in Rabi-coupled Bose mixtures.

Sci Rep 2017 Oct 17;7(1):13358. Epub 2017 Oct 17.

Dipartimento di Fisica e Astronomia "Galileo Galilei", Università di Padova, via Marzolo 8, 35131, Padova, Italy.

Laser induced transitions between internal states of atoms have been playing a fundamental role to manipulate atomic clouds for many decades. In absence of interactions each atom behaves independently and their coherent quantum dynamics is described by the Rabi model. Since the experimental observation of Bose condensation in dilute gases, static and dynamical properties of multicomponent quantum gases have been extensively investigated. Read More

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October 2017
1 Read

Shedding Light on the Photoisomerization Pathway of Donor-Acceptor Stenhouse Adducts.

J Am Chem Soc 2017 11 27;139(44):15596-15599. Epub 2017 Oct 27.

Centre for Systems Chemistry, Stratingh Institute for Chemistry, University of Groningen , Nijenborgh 4, 9747 AG Groningen, The Netherlands.

Donor-acceptor Stenhouse adducts (DASAs) are negative photochromes that hold great promise for a variety of applications. Key to optimizing their switching properties is a detailed understanding of the photoswitching mechanism, which, as yet, is absent. Here we characterize the actinic step of DASA-photoswitching and its key intermediate, which was studied using a combination of ultrafast visible and IR pump-probe spectroscopies and TD-DFT calculations. Read More

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November 2017
12 Reads

Measuring molecular frequencies in the 1-10 μm range at 11-digits accuracy.

Sci Rep 2017 Oct 6;7(1):12780. Epub 2017 Oct 6.

Istituto Nazionale di Ottica-CNR & Dipartimento di Fisica e Astronomia, Università di Firenze & European Laboratory for Non-Linear Spectroscopy LENS, Via Nello Carrara 1, 50019, Sesto Fiorentino, Italy.

High-resolution spectroscopy in the 1-10 μm region has never been fully tackled for the lack of widely-tunable and practical light sources. Indeed, all solutions proposed thus far suffer from at least one of three issues: they are feasible only in a narrow spectral range; the power available for spectroscopy is limited; the frequency accuracy is poor. Here, we present a setup for high-resolution spectroscopy, whose approach can be applied in the whole 1-10 μm range. Read More

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October 2017
1 Read

Photonic Microhand with Autonomous Action.

Adv Mater 2017 Nov 4;29(42). Epub 2017 Oct 4.

European Laboratory for Non Linear Spectroscopy (LENS), University of Florence, Via Nello Carrara 1, 50019, Sesto Fiorentino, Italy.

Grabbing and holding objects at the microscale is a complex function, even for microscopic living animals. Inspired by the hominid-type hand, a microscopic equivalent able to catch microelements is engineered. This microhand is light sensitive and can be either remotely controlled by optical illumination or can act autonomously and grab small particles on the basis of their optical properties. Read More

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November 2017

Area Prostriata in the Human Brain.

Curr Biol 2017 Oct 28;27(19):3056-3060.e3. Epub 2017 Sep 28.

Department of Translational Research on New Technologies in Medicine and Surgery, University of Pisa, via Savi 10, 56126 Pisa, Italy; Stella Maris Scientific Institute, Viale del Tirreno, 331, 56128 Calambrone, Italy.

Area prostriata is a cortical area at the fundus of the calcarine sulcus, described anatomically in humans [1-5] and other primates [6-9]. It is lightly myelinated and lacks the clearly defined six-layer structure evident throughout the cerebral cortex, with a thinner layer 4 and thicker layer 2 [10], characteristic of limbic cortex [11]. In the marmoset and rhesus monkey, area prostriata has cortical connections with MT+ [12], the cingulate motor cortex [8], the auditory cortex [13], the orbitofrontal cortex, and the frontal polar cortices [14]. Read More

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October 2017
9 Reads

Polarization Dependence of Bulk Ion Acceleration from Ultrathin Foils Irradiated by High-Intensity Ultrashort Laser Pulses.

Phys Rev Lett 2017 Aug 2;119(5):054801. Epub 2017 Aug 2.

Centre for Plasma Physics, School of Mathematics and Physics, Queen's University Belfast, Belfast BT7 1NN, United Kingdom.

The acceleration of ions from ultrathin (10-100 nm) carbon foils has been investigated using intense (∼6×10^{20} W  cm^{-2}) ultrashort (45 fs) laser pulses, highlighting a strong dependence of the ion beam parameters on the laser polarization, with circularly polarized (CP) pulses producing the highest energies for both protons and carbons (25-30  MeV/nucleon); in particular, carbon ion energies obtained employing CP pulses were significantly higher (∼2.5 times) than for irradiations employing linearly polarized pulses. Particle-in-cell simulations indicate that radiation pressure acceleration becomes the dominant mechanism for the thinnest targets and CP pulses. Read More

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August 2017
2 Reads

Behavior of Supercritical Fluids across the "Frenkel Line".

J Phys Chem Lett 2017 Oct 29;8(20):4995-5001. Epub 2017 Sep 29.

Dipartimento di Fisica, Universita di Roma La Sapienza , I-00185 Roma, Italy.

The "Frenkel line" (FL), the thermodynamic locus where the time for a particle to move by its size equals the shortest transverse oscillation period, has been proposed as a boundary between recently discovered liquid-like and gas-like regions in supercritical fluids. We report a simulation study of isothermal supercritical neon in a range of densities intersecting the FL. Specifically, structural properties and single-particle and collective dynamics are scrutinized to unveil the onset of any anomalous behavior at the FL. Read More

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October 2017

Spectral purity and tunability of terahertz quantum cascade laser sources based on intracavity difference-frequency generation.

Sci Adv 2017 Sep 1;3(9):e1603317. Epub 2017 Sep 1.

National Enterprise for nanoScience and nanoTechnology (NEST), CNR-Istituto Nanoscienze and Scuola Normale Superiore, Piazza San Silvestro 12, 56127 Pisa, Italy.

Terahertz sources based on intracavity difference-frequency generation in mid-infrared quantum cascade lasers (THz DFG-QCLs) have recently emerged as the first monolithic electrically pumped semiconductor sources capable of operating at room temperature across the 1- to 6-THz range. Despite tremendous progress in power output, which now exceeds 1 mW in pulsed and 10 μW in continuous-wave regimes at room temperature, knowledge of the major figure of merits of these devices for high-precision spectroscopy, such as spectral purity and absolute frequency tunability, is still lacking. By exploiting a metrological grade system comprising a terahertz frequency comb synthesizer, we measure, for the first time, the free-running emission linewidth (LW), the tuning characteristics, and the absolute center frequency of individual emission lines of these sources with an uncertainty of 4 × 10. Read More

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September 2017
12 Reads

Triplet Excited State of BODIPY Accessed by Charge Recombination and Its Application in Triplet-Triplet Annihilation Upconversion.

J Phys Chem A 2017 Oct 27;121(40):7550-7564. Epub 2017 Sep 27.

LENS (European Laboratory for Non-Linear Spectroscopy) , Via N. Carrara 1, 50019 Sesto Fiorentino, Italy.

The triplet excited state properties of two BODIPY phenothiazine dyads (BDP-1 and BDP-2) with different lengths of linker and orientations of the components were studied. The triplet state formation of BODIPY chromophore was achieved via photoinduced electron transfer (PET) and charge recombination (CR). BDP-1 has a longer linker between the phenothiazine and the BODIPY chromophore than BDP-2. Read More

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October 2017
39 Reads

Control of entanglement dynamics in a system of three coupled quantum oscillators.

Sci Rep 2017 Aug 30;7(1):9957. Epub 2017 Aug 30.

Istituto Nazionale di Ottica-CNR Largo E. Fermi 6, 50125, Firenze, Italy.

Dynamical control of entanglement and its connection with the classical concept of instability is an intriguing matter which deserves accurate investigation for its important role in information processing, cryptography and quantum computing. Here we consider a tripartite quantum system made of three coupled quantum parametric oscillators in equilibrium with a common heat bath. The introduced parametrization consists of a pulse train with adjustable amplitude and duty cycle representing a more general case for the perturbation. Read More

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August 2017
7 Reads

Measurement-Induced Strong Kerr Nonlinearity for Weak Quantum States of Light.

Phys Rev Lett 2017 Jul 5;119(1):013601. Epub 2017 Jul 5.

Istituto Nazionale di Ottica (INO-CNR), Largo E. Fermi 6, 50125 Florence, Italy.

Strong nonlinearity at the single photon level represents a crucial enabling tool for optical quantum technologies. Here we report on experimental implementation of a strong Kerr nonlinearity by measurement-induced quantum operations on weak quantum states of light. Our scheme coherently combines two sequences of single photon addition and subtraction to induce a nonlinear phase shift at the single photon level. Read More

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Thermometry of bosonic mixtures in Optical Lattices via Demixing.

Sci Rep 2017 Jul 11;7(1):5105. Epub 2017 Jul 11.

Department of Applied Science and Technology and u.d.r. CNISM, Politecnico di Torino, I-10129, Torino, Italy.

Motivated by recent experiments and theoretical investigations on binary mixtures, we investigate the miscible-immiscible transition at finite temperature by means of Quantum Monte Carlo. Based on the observation that the segregated phase is strongly affected by temperature, we propose to use the degree of demixing for thermometry of a binary bosonic mixture trapped in an optical lattice. We show that the proposed method is especially sensitive at low temperatures, of the order of the tunnelling amplitude, and therefore is particularly suitable in the regime where quantum magnetism is expected. Read More

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