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Bartalini S.,CNR Institute of Neuroscience | Bartalini S.,European Laboratory for Nonlinear Spectroscopy LENS | Borri S.,CNR Institute of Neuroscience | Borri S.,European Laboratory for Nonlinear Spectroscopy LENS | And 11 more authors.
Optics Express | Year: 2011

The frequency-noise power spectral density of a roomtemperature distributed-feedback quantum cascade laser emitting at λ = 4.36 μm has been measured. An intrinsic linewidth value of 260 Hz is retrieved, in reasonable agreement with theoretical calculations. A noise reduction of about a factor 200 in most of the frequency interval is also found, with respect to a cryogenic laser at the same wavelength. A quantitative treatment shows that it can be explained by a temperature-dependent mechanism governing the transport processes in resonant tunnelling devices. This confirms the predominant effect of the heterostructure in determining shape and magnitude of the frequency noise spectrum in QCLs. © 2011 Optical Society of America.


Muniz-Miranda M.,University of Florence | Muniz-Miranda M.,European Laboratory for Nonlinear Spectroscopy LENS | Gellini C.,University of Florence | Gellini C.,European Laboratory for Nonlinear Spectroscopy LENS | Giorgetti E.,CNR Institute of Neuroscience
Journal of Physical Chemistry C | Year: 2011

Copper colloidal nanoparticles are obtained by laser ablation in aqueous solutions of ligands by nanosecond laser pulses at 532 and 1064 nm and examined by localized surface plasmon resonance (LSPR) and surface-enhanced Raman scattering (SERS) spectroscopy, along with transmission electron microscopy (TEM) and zeta potential measurements. This fabrication method, besides providing SERS-active substrates without spectral interferences of reagents, as it generally occurs for the chemical reduction of metal ions, allows obtaining colloidal suspensions which are stable in time because the copper particles are capped by ligand molecules as long as they are formed by laser ablation. This prevents aggregation among metal nanoparticles and probably reduces overall oxidation of the copper surface. © 2011 American Chemical Society.


Martin-Cano D.,Max Planck Institute for the Science of Light | Martin-Cano D.,Center for Quantum Science and Technology in Arcetri | Haakh H.R.,Max Planck Institute for the Science of Light | Murr K.,CNR Institute of Neuroscience | And 6 more authors.
Physical Review Letters | Year: 2014

We investigate the reduction of the electromagnetic field fluctuations in resonance fluorescence from a single emitter coupled to an optical nanostructure. We find that such hybrid systems can lead to the creation of squeezed states of light, with quantum fluctuations significantly below the shot-noise level. Moreover, the physical conditions for achieving squeezing are strongly relaxed with respect to an emitter in free space. A high degree of control over squeezed light is feasible both in the far and near fields, opening the pathway to its manipulation and applications on the nanoscale with state-of-the-art setups. © 2014 American Physical Society.


Muniz-Miranda M.,University of Florence | Muniz-Miranda M.,European Laboratory for Nonlinear Spectroscopy LENS
Applied Catalysis B: Environmental | Year: 2014

Nitrophenols represent common environmental pollutants because of their toxicity and resistance to microbial degradation. In the present work the SERS (surface-enhanced Raman scattering) spectroscopy has been applied to Ag/titania colloidal nanocomposites to monitor the catalytic reduction of 4-nitrophenol under UV irradiation and identify the reaction products. © 2013 Elsevier B.V.


Petrovic J.,European Laboratory for Nonlinear Spectroscopy LENS | Petrovic J.,Vinča Institute of Nuclear Sciences | Herrera I.,European Laboratory for Nonlinear Spectroscopy LENS | Lombardi P.,European Laboratory for Nonlinear Spectroscopy LENS | And 4 more authors.
New Journal of Physics | Year: 2013

Matter-wave interferometry is a powerful tool for high-precision measurements of the quantum properties of atoms, many-body phenomena and gravity. The most precise matter-wave interferometers exploit the excellent localization in momentum space and coherence of the degenerate gases. Further enhancement of the sensitivity and reduction of complexity are crucial conditions for the success and widening of their applications. Here we introduce a multi-state interferometric scheme that offers advances in both these aspects. The coherent coupling between Bose-Einstein condensates in different Zeeman states is used to generate high-harmonic output signals with an enhanced resolution and the maximum possible interferometric visibility. We demonstrate the realization of such an interferometer as a compact, easy to use, atom-chip device. This provides an alternative method for the measurement of the light-atom and surface-atom interactions and enables the application of multi-parameter sensing schemes in cold-atom interferometry. © IOP Publishing and Deutsche Physikalische Gesellschaft.


Volkov V.,Max Planck Institute for Polymer Research | Righini R.,European Laboratory for Nonlinear Spectroscopy LENS
Physical Chemistry Chemical Physics | Year: 2014

While tetracyclines are in active medical use, their bioactive atomic compositions are still questionable. Here, we investigate the structural properties of neutral tetracycline in dimethyl sulfoxide-the environment used often to mimic the environment in vivo. We compare the measured linear and nonlinear infrared spectra to those calculated for a collection of stable and energetically plausible tautomers, and describe the structurally sensitive off-diagonal peaks using anharmonicities of the normal modes. The comparison of experimental and theoretical 2DIR spectra is consistent with the numerical predictions of statistical thermodynamics on the relative weights of possible tautomers. In result, we provide the systematic account of the structural realizations of neutral tetracycline in DMSO. © 2014 the Owner Societies.


Fedyanin D.Y.,Moscow Institute of Physics and Technology | Agio M.,CNR Institute of Neuroscience | Agio M.,European Laboratory for Nonlinear Spectroscopy LENS | Agio M.,Center for Quantum Science and Technology in Arcetri | Agio M.,University of Siegen
New Journal of Physics | Year: 2016

The recently demonstrated electroluminescence of color centers in diamond makes them one of the best candidates for room temperature single-photon sources. However, the reported emission rates are far off what can be achieved by state-of-the-art electrically driven epitaxial quantum dots. Since the electroluminescence mechanism has not yet been elucidated, it is not clear to what extent the emission rate can be increased. Here we develop a theoretical framework to study single-photon emission from color centers in diamond under electrical pumping. The proposed model comprises electron and hole trapping and releasing, transitions between the ground and excited states of the color center as well as structural transformations of the center due to carrier trapping. It provides the possibility to predict both the photon emission rate and the wavelength of emitted photons. Self-consistent numerical simulations of the single-photon emitting diode based on the proposed model show that the photon emission rate can be as high as 100 kcounts s-1 at standard conditions. In contrast to most optoelectronic devices, the emission rate steadily increases with the device temperature achieving of more than 100 Mcount s-1 at 500 K, which is highly advantageous for practical applications. These results demonstrate the potential of color centers in diamond as electrically driven non-classical light emitters and provide a foundation for the design and development of single-photon sources for optical quantum computation and quantum communication networks operating at room and higher temperatures. © 2016 IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.


Wu J.-H.,Northeast Normal University | Artoni M.,European Laboratory for Nonlinear Spectroscopy LENS | Artoni M.,University of Brescia | La Rocca G.C.,Normal School of Pisa
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2015

Lossy atomic photonic crystals can be suitably tailored so that the real and imaginary parts of the susceptibility are, respectively, an odd and an even function of position. Such a parity-time (PT) space antisymmetry in the susceptibility requires neither optical gain nor negative refraction, but is rather attained by a combined control of the spatial modulation of both the atomic density and their dynamic level shift. These passive photonic crystals made of dressed atoms are characterized by a tunable unidirectional reflectionlessness accompanied by an appreciable degree of transmission. Interestingly, such peculiar properties are associated with non-Hermitian degeneracies of the crystal scattering matrix, which can then be directly observed through reflectivity measurements via a straightforward phase modulation of the atomic dynamic level shift and even off resonance. © 2015 American Physical Society.


Giusfredi G.,CNR Institute of Neuroscience | Giusfredi G.,European Laboratory for Nonlinear Spectroscopy LENS | Bartalini S.,CNR Institute of Neuroscience | Bartalini S.,European Laboratory for Nonlinear Spectroscopy LENS | And 10 more authors.
Physical Review Letters | Year: 2010

We report on a novel approach to cavity ring-down spectroscopy with the sample gas in saturated-absorption regime. This technique allows us to decouple and simultaneously retrieve the empty-cavity background and absorption signal, by means of a theoretical model that we developed and tested. The high sensitivity and frequency precision for spectroscopic applications are exploited to measure, for the first time, the hyperfine structure of an excited vibrational state of O17C12O16 in natural abundance with an accuracy of a few parts in 10-11. © 2010 The American Physical Society.


Artoni M.,European Laboratory for Nonlinear Spectroscopy LENS | Artoni M.,CNR Institute of Neuroscience | Artoni M.,University of Brescia | Zavatta A.,CNR Institute of Neuroscience
Physical Review Letters | Year: 2015

Phase-resonant closed-loop optical transitions can be engineered to achieve broadly tunable light phase shifts. Such a novel phase-by-phase control mechanism does not require a cavity and is illustrated here for an atomic interface where a classical light pulse undergoes radian level phase modulations all-optically controllable over a few micron scale. It works even at low intensities and hence may be relevant to new applications of all-optical weak-light signal processing. © 2015 American Physical Society.

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