169 research outputs found
Data for "Ultrafast Spin-Charge Conversion at SnBi2Te4/Co Topological Insulator Interfaces Probed by Terahertz Emission Spectroscopy"
No full textData for "Ultrafast Spin-Charge Conversion at SnBi2Te4/Co Topological Insulator Interfaces Probed by Terahertz Emission Spectroscopy"
(https://onlinelibrary.wiley.com/doi/abs/10.1002/adom.202102061 and https://arxiv.org/pdf/2203.08756.pdf)
E Rongione, S Fragkos, L Baringthon, J Hawecker, E Xenogiannopoulou, P Tsipas, C Song, M Mičica, J Mangeney, J Tignon, T Boulier, N Reyren, R Lebrun, J‐M George, P Le Fèvre, S Dhillon, A Dimoulas, H Jaffrè
Pump-probe denegerate scattering of polaritons in a multiple microcavity.
No full textCommunication oraleMicrocavity polaritons are mixed states of confined photons and quantum well excitons. They inherit interesting properties from each of their two strongly-coupled components. Their excitonic part brings Coulomb interaction, and the photonic part brings cavity amplification and steep dispersion. Polaritons are particularly subject to parametric processes or four-wave mixing. Parametric amplification and oscillation have been observed in 2D single microcavities [1], in a “magic-angle" configuration. Engineering the geometry of the cavities allows overcoming the limitations of the process configuration in these microcavities, governed by conservation of energy and impulsion. Over the last years, disks, rings, wires [2] or pillars have been studied in addition to conventional 2D single microcavities. Multiple planar microcavities are another variant that allows new configurations to be studied. Several cavities can be stacked on top of each other, and coupled by their Bragg intermediate mirrors. Appropriate coupling results in several delocalized modes, where interbranch parametric processes can occur. The set of fourwave mixing configurations that conserve both energy and wave-vectors is consequently much richer. For example, parametric amplification and oscillation have been observed in a triple cavity in an angle-degenerate configuration [3,4]. Here we study parametric interaction in an energy-degenerate configuration. This situation is interesting because individual beams are spatially separated and can eventually be individually analyzed for other properties, such as noise and correlations, which are expected to show non-classical effects. In the present work, we concentrate on power dependences and polarization properties in a triple AlGaAs microcavity embedding InGaAs QWs. First, we demonstrate optical parametric amplification using a pump-probe geometry and cw Ti:Sa excitation (at 4K). Second, we study the idler polarization when varying the pump-probe relative polarization. The efficiency of the parametric amplification depends on the relative polarization of the pump, probe and idler beams in a way that is intrinsically related to the ratio of the coupling constants that characterize the polariton-polariton interaction strenght, for polaritons with parallel or antiparallel spins [5]. Here, we demonstrate that the ratio of these coupling constants can be determined in a very straightforward experiment. References [1] P. G. Savvidis et al., Phy. Rev. Lett. 84, 1547 (2000); M. Saba et al., Nature 414, 731 (2001). [2] G. Dasbach et al., Phys. Rev. B 71, 161308 (2005). [3] C. Diederichs and J. Tignon, Appl. Phys. Lett. 87, 251107 (2005). [4] C. Diederichs et al., Nature 440, 904 (2006) ; D. Taj et al., Phys. Rev. B 80, 081308 (2009). [5] I.A. Shelykh et al., Semicond. Sci. Technol. 25, 013001 (2010)
Polarization properties of polariton-polariton parametric interaction in a multiple microcavity
No full textCommunication oraleMicrocavity polaritons are mixed states of confined photons and quantum well excitons. They inherit interesting properties from each of their two strongly-coupled components. Their excitonic part brings Coulomb interaction, and the photonic part brings cavity amplification and steep dispersion. Polaritons are particularly subject to parametric processes or four-wave mixing. Parametric amplification and oscillation have been observed in 2D single microcavities [1], in a “magic-angle" configuration. Engineering the geometry of the cavities allows overcoming the limitations of the process configuration in these microcavities, governed by conservation of energy and impulsion. Over the last years, disks, rings, wires [2] or pillars have been studied in addition to conventional 2D single microcavities. Multiple planar microcavities are another variant that allows new configurations to be studied. Several cavities can be stacked on top of each other, and coupled by their Bragg intermediate mirrors. Appropriate coupling results in several delocalized modes, where interbranch parametric processes can occur. The set of four-wave mixing configurations that conserve both energy and wave-vectors is consequently much richer. For example, parametric amplification and oscillation have been observed in a triple cavity in an angle-degenerate configuration [3,4]. Here we study parametric interaction in an energy-degenerate configuration. This situation is interesting because individual beams are spatially separated and can eventually be individually analyzed for other properties, such as noise and correlations, which are expected to show non-classical effects. In the present work, we concentrate on power dependences and polarization properties in a triple AlGaAs microcavity embedding InGaAs QWs. First, we demonstrate optical parametric amplification using a pump-probe geometry and cw Ti:Sa excitation (at 4K). Second, we study the idler polarization when varying the pumpprobe relative polarization. The efficiency of the parametric amplification depends on the relative polarization of the pump, probe and idler beams in a way that is intrinsically related to the ratio of the coupling constants that characterize the polariton-polariton interaction strenght, for polaritons with parallel or antiparallel spins [5]. Here, we demonstrate that the ratio of these coupling constants can be determined in a very straightforward experiment. [1] P. G. Savvidis et al., Phy. Rev. Lett. 84, 1547 (2000); M. Saba et al., Nature 414, 731 (2001). [2] G. Dasbach et al., Phys. Rev. B 71, 161308 (2005). [3] C. Diederichs and J. Tignon, Appl. Phys. Lett. 87, 251107 (2005). [4] C. Diederichs et al., Nature 440, 904 (2006) ; D. Taj et al., Phys. Rev. B 80, 081308 (2009). [5] I.A. Shelykh et al., Semicond. Sci. Technol. 25, 013001 (2010)
Revisionary notes on Bentonia van Achterberg, 1992 (Hymenoptera: Braconidae: Orgilinae) with description of two new species
No full textTwo new species of the genus Bentonia van Achterberg, 1992 (Braconidae: Orgilinae) (B. inca from Peru and B. xochiquetzalis from Mexico) are described and partly illustrated. A third undescribed species was found for which some characters are listed. The distribution of B. scutellaris van Achterberg, 1992, is extended west to Peru and B. longicornis van Achterberg, 1992, north to Venezuela. An identification key is added
Turing patterns in semiconductor microcavities : formation and optical control
No full textCommunication oraleTuring pattern formation in nonlinear systems attracts great interest in fields as varied as biology, chemistry and physics [1,2]. Here, we show that patterns can also be formed in semiconductor microcavities operated in the optical parametric oscillation (OPO) regime [3,4]. The basic process involved is the very efficient polariton-polariton scattering, induced mostly by the Coulomb interaction that induces strong resonant χ (3) nonlinearities [3]. In this context, coupled planar microcavities [4] offer a unique test-bed for studying the formation of patterns. The sample design allows engineering multiple polariton modes that can be tuned at will [4]. The system can be resonantly pumped at normal incidence inducing interbranch energy-degenerate OPO. With respect to other studied patterns (e.g. in hydrodynamics or in conventional OPOs), the originality relies here with: (i) the excitation and emitted beams wave-vectors can be easily accessed and controlled; (ii) the particular role played by the polarization of light and the polariton spin; (iii) the perspective given to use such semiconductor nanostructures to realize fast optical- switches. Here, we demonstrate the formation of hexagonal patterns observed in the OPO far-field emission as well as in the real space. We then prove that these patterns can be optically controlled by changing the pump wave-vector as well as by modifying the polarization of the pump beam. Finally an all-optical switch is demonstrated. 1] M.C. Cross and P. Hohenberg, Rev. Mod. Phys. 65,851 (1993). [2] A. Turing,Phil. Trans.. R. Soc. Lonf. B 237, 37 (1952). [3] P. G. Savvidis, J. J. Baumberg, R. M. Stevenson, M. S. Skolnick, D. M. Whittaker, J. S. Roberts, Phys. Rev. Lett. 84, 1547 (2000). [4] C. Diederichs, J. Tignon, G. Dasbach, C. Ciuti, A. Lemaitre, J. Bloch, Ph. Roussignol, C. Delalande , Nature 410, 904 (2006)
Turing patterns in semiconductor microcavities : formation and optical control
No full textCommunication oraleTuring pattern formation in nonlinear systems attracts great interest in fields as varied as biology, chemistry and physics [1,2]. Here, we show that patterns can also be formed in semiconductor microcavities operated in the optical parametric oscillation (OPO) regime [3,4]. The basic process involved is the very efficient polariton-polariton scattering, induced mostly by the Coulomb interaction that induces strong resonant χ (3) nonlinearities [3]. In this context, coupled planar microcavities [4] offer a unique test-bed for studying the formation of patterns. The sample design allows engineering multiple polariton modes that can be tuned at will [4]. The system can be resonantly pumped at normal incidence inducing interbranch energy-degenerate OPO. With respect to other studied patterns (e.g. in hydrodynamics or in conventional OPOs), the originality relies here with: (i) the excitation and emitted beams wave-vectors can be easily accessed and controlled; (ii) the particular role played by the polarization of light and the polariton spin; (iii) the perspective given to use such semiconductor nanostructures to realize fast optical- switches. Here, we demonstrate the formation of hexagonal patterns observed in the OPO far-field emission as well as in the real space. We then prove that these patterns can be optically controlled by changing the pump wave-vector as well as by modifying the polarization of the pump beam. Finally an all-optical switch is demonstrated. 1] M.C. Cross and P. Hohenberg, Rev. Mod. Phys. 65,851 (1993). [2] A. Turing,Phil. Trans.. R. Soc. Lonf. B 237, 37 (1952). [3] P. G. Savvidis, J. J. Baumberg, R. M. Stevenson, M. S. Skolnick, D. M. Whittaker, J. S. Roberts, Phys. Rev. Lett. 84, 1547 (2000). [4] C. Diederichs, J. Tignon, G. Dasbach, C. Ciuti, A. Lemaitre, J. Bloch, Ph. Roussignol, C. Delalande , Nature 410, 904 (2006)
Epidemiology and genetic characterization of equine infectious anaemia virus strains isolated in Belgium in 2010.
No full text<p>In January 2010, the United Kingdom notified cases of equine infectious anaemia (EIA) in two horses introduced from Belgium. The animals came from one assembly centre in Romania and had transited through Belgium with 16 other horses. Nine of them, bought by a Belgian horse breeder, were investigated in Belgium and revealed one additional EIA-positive animal. Afterwards, the Belgian Federal Agency for the Safety of the Food Chain (FASFC) organized a serological EIA survey of the horses introduced into Belgium from Romania between 2007 and 2009. Among the 95 horses identified, six additional serological positive cases were found that had been introduced into Belgium in 2008 (n = 4) and in 2009 (n = 2). The survey was extended to the horses in contact with the positive cases, but all contact animals were negative, indicating the absence of transmission. Virological examination performed on tissue samples collected from two seropositive animals demonstrated the presence of viral DNA of EIA virus. Phylogenetic analysis based on the sequences of EIA virus gag gene clustered the Belgian isolates with Romanian strains isolated in 2009. The presumption of a common Belgian origin could be rejected.</p></p
Amplified Fragments Length Polymorphism Between Populations Of Amblystegium Tenax Exposed To Contrasting Water Chemistries
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Optique non-linéaire résonante et contrôle de la phase des lasers à cascade quantique
No full textLes lasers à cascade quantique (LCQ) sont des nanostructures de semiconducteurs se basant sur des transitions intersousbandes entre états confinés de la bande de conduction. Ils ont permis de combler un manque de sources puissantes et compactes d abord dans le moyen infrarouge (MIR) puis dans le térahertz (THz). Cette thèse présente deux études en rapport avec ces lasers. La première partie présente les propriétés d optique non-linéaire résonantes des LCQ. Il s agit de démontrer la génération de différence de fréquences entre un faisceau proche infrarouge (IR) et le champ THz du LCQ. L excitation proche IR est résonante avec les transitions interbandes des puits quantiques qui composent le LCQ. Ceci exalte la susceptibilité non-linéaire du milieu. Le champ THz intense dans la cavité combiné à cette excitation résonante permet d obtenir de bonnes efficacités (jusqu à 0.13%) et de générer des harmoniques supérieures jusqu à l ordre 3. Ces interactions non-linéaires ont également été étudiées dans les LCQ MIR ce qui a permis d augmenter la température de fonctionnement jusqu à 275 K. Une deuxième partie traite du contrôle de la phase du champ THz d'un LCQ au moyen d'un montage de spectroscopie THz dans le domaine temporel. L'originalité résulte dans l'usage d'un LCQ ayant un guide double métal. Ces guides permettent d'avoir de meilleures performances en température mais ont des dimensions largement sous longueur d'onde. Ces dimensions compliquent le couplage d'une onde THz externe nécessaire à l'amorçage du champ THz du LCQ sur une phase fixe. Des antennes en forme de V sont déposées à la surface du LCQ pour faire une adaptation d impédance et favoriser ainsi le couplage.Quantum cascade lasers (QCL) are semiconductor nanostructures based on inter-subband transitions between confined states in the conduction band. They filled the lack of compact and powerful sources in the mid-infrared (MIR) and in the terahertz (THz) range. This thesis presents two studies on these lasers. First part investigates resonant optical nonlinearities of QCL. We show difference frequency generation between a near-infrared (NIR) beam and the QCL THz field, i.e. at ENIR-EQCL. NIR excitation is resonant with interband transitions in the QCL active region, enhancing the nonlinear susceptibility of the matter. High intracavity THz field combined with the resonant NIR beam results in good efficiencies for the frequency mixing (0.13%) and in high order generation up to the third order (EIR-3EQCL). For the first time this nonlinear interaction is investigated within a MIR QCL. This allows demonstrating the nonlinear interaction up to 275 K, showing that the interaction is temperature independent. The second part deals with phase control of QCL emission via THz time domain spectroscopy. The novelty is the use of a Metal-Metal (MM) waveguide. These guides lead to higher temperature operations but have sub-wavelength dimensions (~10 m compared to 100 m for the emission). These dimensions make harder the coupling of a THz seed which is required to initiate the THz QCL field. V shape antennas are processed above QCL facets to match the impedance between free-space and guided modes. Thus, coupling efficiency and power extraction are enhanced. We demonstrate that we can phase-lock the emission of a MM QCL by THz injection seeding and resolve its amplitude and its phase.PARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF
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