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  1. Article ; Online: Penrose Superradiance in Nonlinear Optics.

    Braidotti, Maria Chiara / Faccio, Daniele / Wright, Ewan M

    Physical review letters

    2020  Volume 125, Issue 19, Page(s) 193902

    Abstract: Particles or waves scattered from a rotating black hole can be amplified through the process of Penrose superradiance, although this cannot currently be observed in an astrophysical setting. Here we theoretically show that analog Penrose superradiance ... ...

    Abstract Particles or waves scattered from a rotating black hole can be amplified through the process of Penrose superradiance, although this cannot currently be observed in an astrophysical setting. Here we theoretically show that analog Penrose superradiance arises naturally in the field of nonlinear optics. A loosely focused signal beam can experience gain or amplification as it glances off a strong vortex pump beam in a nonlinear defocusing medium. Amplification occurs only with the generation and trapping of negative norm modes in the core of the pump vortex, as predicted by Penrose. Our results elucidate a new regime of nonlinear optics involving the notion of an ergoregion, providing further insight into the processes and transient dynamics involved in Penrose superradiance.
    Language English
    Publishing date 2020-11-20
    Publishing country United States
    Document type Journal Article
    ZDB-ID 208853-8
    ISSN 1079-7114 ; 0031-9007
    ISSN (online) 1079-7114
    ISSN 0031-9007
    DOI 10.1103/PhysRevLett.125.193902
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Article ; Online: Measurement of Penrose Superradiance in a Photon Superfluid.

    Braidotti, Maria Chiara / Prizia, Radivoje / Maitland, Calum / Marino, Francesco / Prain, Angus / Starshynov, Ilya / Westerberg, Niclas / Wright, Ewan M / Faccio, Daniele

    Physical review letters

    2022  Volume 128, Issue 1, Page(s) 13901

    Abstract: The superradiant amplification in the scattering from a rotating medium was first elucidated by Sir Roger Penrose over 50 years ago as a means by which particles could gain energy from rotating black holes. Despite this fundamental process being ... ...

    Abstract The superradiant amplification in the scattering from a rotating medium was first elucidated by Sir Roger Penrose over 50 years ago as a means by which particles could gain energy from rotating black holes. Despite this fundamental process being ubiquitous also in wave physics, it has only been observed once experimentally, in a water tank. Here, we measure this amplification for a nonlinear optics experiment in the superfluid regime. In particular, by focusing a weak optical beam carrying orbital angular momentum onto the core of a strong pump vortex beam, negative norm modes are generated and trapped inside the vortex core, allowing for amplification of a reflected beam. Our experiment demonstrates amplified reflection due to a novel form of nonlinear optical four-wave mixing, whose phase-relation coincides with the Zel'dovich-Misner condition for Penrose superradiance in our photon superfluid, and unveil the role played by negative frequency modes in the process.
    Language English
    Publishing date 2022-01-21
    Publishing country United States
    Document type Journal Article
    ZDB-ID 208853-8
    ISSN 1079-7114 ; 0031-9007
    ISSN (online) 1079-7114
    ISSN 0031-9007
    DOI 10.1103/PhysRevLett.128.013901
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  3. Article ; Online: Time-of-Flight Imaging at 10 ps Resolution with an ICCD Camera.

    Cester, Lucrezia / Lyons, Ashley / Braidotti, Maria Chiara / Faccio, Daniele

    Sensors (Basel, Switzerland)

    2019  Volume 19, Issue 1

    Abstract: ICCD cameras can record low light events with extreme temporal resolution. Thus, they are used in a variety of bio-medical applications for single photon time of flight measurements and LIDAR measurements. In this paper, we present a method which allows ... ...

    Abstract ICCD cameras can record low light events with extreme temporal resolution. Thus, they are used in a variety of bio-medical applications for single photon time of flight measurements and LIDAR measurements. In this paper, we present a method which allows improvement of the temporal resolution of ICCD cameras down to 10 ps (from the native 200 ps of our model), thus placing ICCD cameras at a better temporal resolution than SPAD cameras and in direct competition with streak cameras. The higher temporal resolution can serve for better tracking and visualization of the information carried in time-of-flight measurements.
    Language English
    Publishing date 2019-01-06
    Publishing country Switzerland
    Document type Journal Article
    ZDB-ID 2052857-7
    ISSN 1424-8220 ; 1424-8220
    ISSN (online) 1424-8220
    ISSN 1424-8220
    DOI 10.3390/s19010180
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  4. Article ; Online: Zel'dovich Amplification in a Superconducting Circuit.

    Braidotti, Maria Chiara / Vinante, Andrea / Gasbarri, Giulio / Faccio, Daniele / Ulbricht, Hendrik

    Physical review letters

    2020  Volume 125, Issue 14, Page(s) 140801

    Abstract: Zel'dovich proposed that electromagnetic (EM) waves with angular momentum reflected from a rotating metallic, lossy cylinder will be amplified. However, we are still lacking a direct experimental EM-wave verification of this fifty-year-old prediction due ...

    Abstract Zel'dovich proposed that electromagnetic (EM) waves with angular momentum reflected from a rotating metallic, lossy cylinder will be amplified. However, we are still lacking a direct experimental EM-wave verification of this fifty-year-old prediction due to the challenging conditions in which the phenomenon manifests itself: the mechanical rotation frequency of the cylinder must be comparable with the EM oscillation frequency. Here, we propose an experimental approach that solves this issue and is predicted to lead to a measurable Zel'dovich amplification with existing superconducting circuit technology. We design a superconducting circuit with low frequency EM modes that couple through free space to a magnetically levitated and spinning microsphere placed at the center of the circuit. We theoretically estimate the circuit EM mode gain and show that rotation of the microsphere can lead to experimentally observable amplification, thus paving the way for the first EM-field experimental demonstration of Zel'dovich amplification.
    Language English
    Publishing date 2020-10-08
    Publishing country United States
    Document type Journal Article
    ZDB-ID 208853-8
    ISSN 1079-7114 ; 0031-9007
    ISSN (online) 1079-7114
    ISSN 0031-9007
    DOI 10.1103/PhysRevLett.125.140801
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  5. Article ; Online: Gamow vectors explain the shock profile.

    Braidotti, Maria Chiara / Gentilini, Silvia / Conti, Claudio

    Optics express

    2016  Volume 24, Issue 19, Page(s) 21963–21970

    Abstract: The description of shock waves beyond the shock point is a challenge in nonlinear physics and optics. Finding solutions to the global dynamics of dispersive shock waves is not always possible due to the lack of integrability. Here we propose a new method ...

    Abstract The description of shock waves beyond the shock point is a challenge in nonlinear physics and optics. Finding solutions to the global dynamics of dispersive shock waves is not always possible due to the lack of integrability. Here we propose a new method based on the eigenstates (Gamow vectors) of a reversed harmonic oscillator in a rigged Hilbert space. These vectors allow analytical formulation for the development of undular bores of shock waves in a nonlinear nonlocal medium. Experiments by a photothermal induced nonlinearity confirm theoretical predictions: the undulation period as a function of power and the characteristic quantized decays of Gamow vectors. Our results demonstrate that Gamow vectors are a novel and effective paradigm for describing extreme nonlinear phenomena.
    Language English
    Publishing date 2016-09-19
    Publishing country United States
    Document type Journal Article
    ZDB-ID 1491859-6
    ISSN 1094-4087 ; 1094-4087
    ISSN (online) 1094-4087
    ISSN 1094-4087
    DOI 10.1364/OE.24.021963
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  6. Article ; Online: Physical realization of the Glauber quantum oscillator.

    Gentilini, Silvia / Braidotti, Maria Chiara / Marcucci, Giulia / DelRe, Eugenio / Conti, Claudio

    Scientific reports

    2015  Volume 5, Page(s) 15816

    Abstract: More than thirty years ago Glauber suggested that the link between the reversible microscopic and the irreversible macroscopic world can be formulated in physical terms through an inverted harmonic oscillator describing quantum amplifiers. Further ... ...

    Abstract More than thirty years ago Glauber suggested that the link between the reversible microscopic and the irreversible macroscopic world can be formulated in physical terms through an inverted harmonic oscillator describing quantum amplifiers. Further theoretical studies have shown that the paradigm for irreversibility is indeed the reversed harmonic oscillator. As outlined by Glauber, providing experimental evidence of these idealized physical systems could open the way to a variety of fundamental studies, for example to simulate irreversible quantum dynamics and explain the arrow of time. However, supporting experimental evidence of reversed quantized oscillators is lacking. We report the direct observation of exploding n = 0 and n = 2 discrete states and Γ0 and Γ2 quantized decay rates of a reversed harmonic oscillator generated by an optical photothermal nonlinearity. Our results give experimental validation to the main prediction of irreversible quantum mechanics, that is, the existence of states with quantized decay rates. Our results also provide a novel perspective to optical shock-waves, potentially useful for applications as lasers, optical amplifiers, white-light and X-ray generation.
    Language English
    Publishing date 2015-11-02
    Publishing country England
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 2615211-3
    ISSN 2045-2322 ; 2045-2322
    ISSN (online) 2045-2322
    ISSN 2045-2322
    DOI 10.1038/srep15816
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  7. Article ; Online: Erratum: Biomimetic antimicrobial cloak by graphene-oxide agar hydrogel.

    Papi, Massimiliano / Palmieri, Valentina / Bugli, Francesca / De Spirito, Marco / Sanguinetti, Maurizio / Ciancico, Carlotta / Braidotti, Maria Chiara / Gentilini, Silvia / Angelani, Luca / Conti, Claudio

    Scientific reports

    2017  Volume 7, Issue 1, Page(s) 2779

    Abstract: A correction to this article has been published and is linked from the HTML version of this paper. The error has not been fixed in the paper. ...

    Abstract A correction to this article has been published and is linked from the HTML version of this paper. The error has not been fixed in the paper.
    Language English
    Publishing date 2017-06-01
    Publishing country England
    Document type Journal Article ; Published Erratum
    ZDB-ID 2615211-3
    ISSN 2045-2322 ; 2045-2322
    ISSN (online) 2045-2322
    ISSN 2045-2322
    DOI 10.1038/s41598-017-00063-5
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  8. Article ; Online: Biomimetic antimicrobial cloak by graphene-oxide agar hydrogel.

    Papi, Massimiliano / Palmieri, Valentina / Bugli, Francesca / De Spirito, Marco / Sanguinetti, Maurizio / Ciancico, Carlotta / Braidotti, Maria Chiara / Gentilini, Silvia / Angelani, Luca / Conti, Claudio

    Scientific reports

    2016  Volume 6, Issue 1, Page(s) 12

    Abstract: Antibacterial surfaces have an enormous economic and social impact on the worldwide technological fight against diseases. However, bacteria develop resistance and coatings are often not uniform and not stable in time. The challenge is finding an ... ...

    Abstract Antibacterial surfaces have an enormous economic and social impact on the worldwide technological fight against diseases. However, bacteria develop resistance and coatings are often not uniform and not stable in time. The challenge is finding an antibacterial coating that is biocompatible, cost-effective, not toxic, and spreadable over large and irregular surfaces. Here we demonstrate an antibacterial cloak by laser printing of graphene oxide hydrogels mimicking the Cancer Pagurus carapace. We observe up to 90% reduction of bacteria cells. This cloak exploits natural surface patterns evolved to resist to microorganisms infection, and the antimicrobial efficacy of graphene oxide. Cell integrity analysis by scanning electron microscopy and nucleic acids release show bacteriostatic and bactericidal effect. Nucleic acids release demonstrates microorganism cutting, and microscopy reveals cells wrapped by the laser treated gel. A theoretical active matter model confirms our findings. The employment of biomimetic graphene oxide gels opens unique possibilities to decrease infections in biomedical applications and chirurgical equipment; our antibiotic-free approach, based on the geometric reduction of microbial adhesion and the mechanical action of Graphene Oxide sheets, is potentially not affected by bacterial resistance.
    Language English
    Publishing date 2016-12-05
    Publishing country England
    Document type Journal Article
    ZDB-ID 2615211-3
    ISSN 2045-2322 ; 2045-2322
    ISSN (online) 2045-2322
    ISSN 2045-2322
    DOI 10.1038/s41598-016-0010-7
    Database MEDical Literature Analysis and Retrieval System OnLINE

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