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Search Results: 1 - 10 of 5122 matches for " Angela Vasanelli "
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Quantum model of coupled intersubband plasmons
Giulia Pegolotti,Angela Vasanelli,Yanko Todorov,Carlo Sirtori
Physics , 2014, DOI: 10.1103/PhysRevB.90.035305
Abstract: We present a quantum model to calculate the dipole-dipole coupling between electronic excitations in the conduction band of semiconductor quantum wells. We demonstrate that the coupling depends on a characteristic length, related to the overlap between microscopic current densities associated with each electronic excitation. As a result of the coupling, a macroscopic polarization is established in the quantum wells, corresponding to one or few bright collective modes of the electron gas. Our model is applied to derive a sum rule and to investigate the interplay between tunnel coupling and Coulomb interaction in the absorption spectrum of a dense electron gas.
Electrically injected cavity polaritons
Luca Sapienza,Angela Vasanelli,Raffaele Colombelli,Cristiano Ciuti,Yannick Chassagneux,Christophe Manquest,Ulf Gennser,Carlo Sirtori
Physics , 2007, DOI: 10.1103/PhysRevLett.100.136806
Abstract: We have realised a semiconductor quantum structure that produces electroluminescence while operating in the light-matter strong coupling regime. The mid-infrared light emitting device is composed of a quantum cascade structure embedded in a planar microcavity, based on the GaAs/AlGaAs material system. At zero bias, the structure is characterised using reflectivity measurements which show, up to room temperature, a wide polariton anticrossing between an intersubband transition and the resonant cavity photon mode. Under electrical injection the spectral features of the emitted light change drastically, as electrons are resonantly injected in a reduced part of the polariton branches. Our experiment demonstrates that electrons can be selectively injected into polariton states up to room temperature.
Polaritonic spectroscopy of intersubband transitions
Yanko Todorov,Lorenzo Tosetto,Aymeric Delteil,Angela Vasanelli,Aaron Maxwel Andrews,Gottfired Strasser,Carlo Sirtori
Physics , 2012, DOI: 10.1103/PhysRevB.86.125314
Abstract: We report on an extensive experimental study of intersubband excitations in the THz range arising from the coupling between a quantum well and a zero-dimensional metal-metal microcavities. Because of the conceptual simplicity of the resonators we obtain an extremely predictable and controllable system to investigate light-matter interaction. The experimental data is modelled by combining a quantum mechanical approach with an effective medium electromagnetic simulation that allows us to take into account the losses of the system. By comparing our modelling with the data we are able to retrieve microscopic information, such as the electronic populations on different subbands as a function of the temperature. Our modelling approach sets the base of a designer tool for intersubband light-matter coupled systems.
Intersubband electroluminescent devices operating in the strong coupling regime
Pierre Jouy,Angela Vasanelli,Yanko Todorov,Luca Sapienza,Raffaele Colombelli,Ulf Gennser,Carlo Sirtori
Physics , 2012, DOI: 10.1103/PhysRevB.82.045322
Abstract: We present a detailed study of the electroluminescence of intersubband devices operating in the light-matter strong coupling regime. The devices have been characterized by performing angle resolved spectroscopy that shows two distinct light intensity spots in the momentum-energy phase diagram. These two features of the electroluminescence spectra are associated with photons emitted from the lower polariton branch and from the weak coupling of the intersubband transition with an excited cavity mode. The same electroluminescent active region has been processed into devices with and without the optical microcavity to illustrate the difference between a device operating in the strong and weak coupling regime. The spectra are very well simulated as the product of the polariton optical density of states, and a function describing the energy window in which the polariton states are populated. The voltage evolution of the spectra shows that the strong coupling regime allows the observation of the electroluminescence at energies otherwise inaccessible.
Coupling of a surface plasmon with localized subwavelength microcavity modes
Pierre Jouy,Yanko Todorov,Angela Vasanelli,Raffaele Colombelli,Isabelle Sagnes,Carlo Sirtori
Physics , 2012, DOI: 10.1063/1.3536504
Abstract: Mid-infrared photonic modes of a periodically patterned metal-dielectric-metal structure have been investigated theoretically and experimentally. We have observed an anticrossing behaviour between cavity modes localized in the double-metal regions and the surface plasmon polariton, signature of a hybridisation between the two modes.
Transition from strong to ultra-strong coupling regime in mid-infrared metal-dielectric-metal cavities
Pierre Jouy,Angela Vasanelli,Yanko Todorov,Aymeric Delteil,Giorgio Biasiol,Lucia Sorba,Carlo Sirtori
Physics , 2012, DOI: 10.1063/1.3598432
Abstract: We have investigated the transition from strong to ultra-strong coupling regime between a mid-infrared intersubband excitation and the fundamental mode of a metal-dielectric-metal microcavity. The ultra-strong coupling regime is demonstrated up to room temperature for a wavelength of $11.7 \mu$m by using 260 nm thick cavities, which impose an extreme sub-wavelength confinement. By varying the doping of our structures we show that the experimental signature of the transition to the ultra-strong coupling regime is the opening of a photonic gap in the polariton dispersion. The width of this gap depends quadratically on the ratio between the Rabi and intersubband transition energies.
Gate controlled coupling of intersubband plasmons
Aymeric Delteil,Angela Vasanelli,Yanko Todorov,Bruno Paulillo,Giorgio Biasiol,Lucia Sorba,Carlo Sirtori
Physics , 2013, DOI: 10.1063/1.4788753
Abstract: The optical response of a heavily doped quantum well, with two occupied subbands, has been investigated as a function of the electronic density. It is shown that the two optically active transitions are mutually coupled by dipole-dipole Coulomb interaction, which strongly renormalizes their absorption amplitude. In order to demonstrate this effect, we have measured a set of optical spectra on a device in which the electronic density can be tuned by the application of a gate voltage. Our results show that the absorption spectra can be correctly described only by taking into account the Coulomb coupling between the two transitions. As a consequence, the optical dipoles originating from intersubband transitions are not independent, but rather coupled oscillators with an adjustable strength.
Photovoltaic Probe of Cavity Polaritons in a Quantum Cascade Structure
Luca Sapienza,Raffaele Colombelli,Angela Vasanelli,Cristiano Ciuti,Christophe Manquest,Ulf Gennser,Carlo Sirtori
Physics , 2007, DOI: 10.1063/1.2739308
Abstract: The strong coupling between an intersubband excitation in a quantum cascade structure and a photonic mode of a planar microcavity has been detected by angle-resolved photovoltaic measurements. A typical anticrossing behavior, with a vacuum-field Rabi splitting of 16 meV at 78K, has been measured, for an intersubband transition at 163 meV. These results show that the strong coupling regime between photons and intersubband excitations can be engineered in a quantum cascade opto-electronic device. They also demonstrate the possibility to perform angle-resolved mid-infrared photodetection and to develop active devices based on intersubband cavity polaritons.
Radiatively broadened thermal emitters
Simon Huppert,Angela Vasanelli,Thibault Laurent,Yanko Todorov,Giulia Pegolotti,Grégoire Beaudoin,Isabelle Sagnes,Carlo Sirtori
Physics , 2015,
Abstract: We study the incandescence of a semiconductor system characterized by a radiatively broadened material excitation. We show that the shape of the emission spectrum and the peak emissivity value are determined by the ratio between radiative and non-radiative relaxation rates of the material mode. Our system is a heavily doped quantum well, exhibiting a collective bright electronic excitation in the mid-infrared. The spontaneous emission rate of this collective mode strongly depends on the emission direction and, uncommonly for a solid-state system, can dominate non-radiative scattering processes. Consequently the incandescence spectrum undergoes strong modifications when the detection angle is varied. Incandescence is modelled solving quantum Langevin equations, including a microscopic description of the collective excitations, decaying into electronic and photonic baths. We demonstrate that the emissivity reaches unity value for a well-defined direction and presents an angular radiative pattern which is very different from that of an oscillating dipole.
Direct surface cyclotron resonance terahertz emission from a quantum cascade structure
Fran?ois-Régis Jasnot,Louis-Anne De Vaulchier,Yves Guldner,Gérald Bastard,Angela Vasanelli,Christophe Manquest,Carlo Sirtori,Mattias Beck,Jér?me Faist
Physics , 2012, DOI: 10.1063/1.3692572
Abstract: A strong magnetic field applied along the growth direction of a semiconductor quantum well gives rise to a spectrum of discrete energy states, the Landau levels. By combining quantum engineering of a quantum cascade structure with a static magnetic field, we can selectively inject electrons into the excited Landau level of a quantum well and realize a tunable surface emitting device based on cyclotron emission. By applying the appropriate magnetic field between 0 and 12 T, we demonstrate emission from a single device over a wide range of frequencies (1-2 THz and 3-5 THz).
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