Messanae Universitas Studiorum: No conditions. Results ordered -Date Deposited. 2017-03-24T17:45:26ZEPrintshttp://cab.unime.it/images/sitelogo.pnghttp://cab.unime.it/mus/2014-04-14T14:59:43Z2014-08-08T07:43:07Zhttp://cab.unime.it/mus/id/eprint/5160This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/51602014-04-14T14:59:43ZDinamica di eccitoni confinati in pozzi quantici di tipo $Zn(S,Se)$ e generazione di seconda armonicaExcitonic properties of $Zn(S,Se)ZnS$ strained materials have been investigated in superlattices and asymmetric quantum wells by an accurate variational envelope function, expanded in electron-hole subbands products. Excitonic binding energy, oscillator strength and absorption spectra have been produced. Second harmonic generation effects ($SHG$) in asymmetric single quantum wells ($ASQWs$) are computed and briefly discussed.Giovanni CrupiG. MartinoRaffaello GirlandaN. TomassiniA. D'AndreaR. Atanasov2009-11-25Z2010-04-13T11:15:16Zhttp://cab.unime.it/mus/id/eprint/522This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/5222009-11-25ZMicroscopic theory of spatially resolved photoluminescence in disordered nanostructures Quantum dots have become objects of extensive research activity because of their applications such as advanced electronic and optoelectronic devices. Here we analyse theoretically the optical properties of dots naturally formed by interface fluctuations in GaAs narrow quantum wells. Specifically we present the simulations of local optical spectroscopy and spatially resolved photoluminescence in quantum wells with interface fluctuations. The theory includes light quantization, acoustic phonon scattering, and inhomogeneous sample-excitation and/or light-detection. Such theoretical framework provides a general basis for the description of spectroscopic imaging. Numerically calculated absorption and photoluminescence images clarify the impact of the near-field optical setup and put forward the potentials of the method for the understanding of near-field light emission from semiconductor quantum structures.
Salvatore SavastaGiovanna MartinoGiuseppe PistoneOmar Di StefanoRaffaello Girlanda2005-06-01Z2012-09-20T08:44:12Zhttp://cab.unime.it/mus/id/eprint/324This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/3242005-06-01ZOptical mapping of amplitude and phase of excitonic wave functions in a quantum dot systemWe propose a technique based on a near-field scanning optical microscope, able to measure the spatial variations of both amplitude and phase of the wave functions of the individual eigenstates of a quantum dot system. The proposed scheme is based on a near-field optical microscope working in collection mode combined with a Mach-Zehnder interferometer. We analyze the response function of this device and present microscopic numerical calculations simulating the measurements. These results show that spatially resolved spectroscopy can go beyond measurements of local density of states and open the way to an optical microscopy that, exploiting the coherence properties of light, is able to provide direct and complete quantum-mechanical information on the spatial variations of solid-state mesoscopic quantum eigenfunctions.Omar Di StefanoSalvatore SavastaGiuseppe PistoneGiovanna MartinoRaffaello Girlanda2005-05-31Z2010-04-13T11:20:36Zhttp://cab.unime.it/mus/id/eprint/319This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/3192005-05-31ZHyper Raman Scattering in Microcavity Quantum Wells: A Quantum Optical Process in the Strong Coupling RegimeWe analyze the hyper Raman scattering process in a quantum well grown inside a semiconductor microcavity and present a microscopic calculation of emission spectra as a function of excitation energy, detuning, and angles. The exciton-photon coupling is treated non-perturbatively to include polariton effects and the Coulomb interaction between electrons is treated beyond the mean field approximation. The observation of hyper Raman scattering in semiconductor microcavities would represent an important step for the realization of non-classical optical states based on excitons. We find that the polaritons emitted in this scattering process are strongly correlated. This correlation,can be efficiently transferred to output photons, resulting in emission of two correlated non-classical light beams. As a probe of the quantum correlation we calculate the output spectrum of fluctuations in the intensity difference of the two beams generated in the hyper Raman process.Salvatore SavastaRaffaello GirlandaGiovanna Martino2005-05-31Z2010-04-13T11:20:24Zhttp://cab.unime.it/mus/id/eprint/320This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/3202005-05-31ZLooking at Localized Excitons in Quantum Structures: A Theoretical DescriptionWe present a theory of scanning local optical spectroscopy in quantum structures taking into account structural disorder. The calculated spatially resolved spectra show the individual spectral lines from the exciton states localized by the disordered potential as well as the quasicontinua spectra at positions close to the potential barriers in agreement with the experimental findings.Omar Di StefanoSalvatore SavastaGiovanna MartinoRaffaello Girlanda2005-05-31Z2010-04-13T11:20:30Zhttp://cab.unime.it/mus/id/eprint/322This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/3222005-05-31ZMany-Body and Correlation Effects on Parametric Polariton Amplification in Semiconductor MicrocavitiesThe complexity induced by the Coulomb interaction between electrons determines the noninstantaneous character of exciton-exciton collisions. We show that the exciton-photon coupling in semiconductor microcavities is able to alter the exciton dynamics during collisions strongly affecting the effective scattering rates. Our analysis clarifies the origin of the great enhancement of parametric gain observed when increasing the polariton splitting. It also demonstrates that exciton-exciton collisions in semiconductors can be controlled and engineered to produce almost decoherence-free collisions for the realization of all-optical microscopic devices.Salvatore SavastaOmar Di StefanoRaffaello Girlanda2005-05-31Z2010-04-13T11:20:19Zhttp://cab.unime.it/mus/id/eprint/325This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/3252005-05-31ZSpectroscopy of four-particle correlations in semiconductor microcavitiesWe present a theory of ultrafast time-resolved pump and probe spectroscopy in semiconductor microcavities. The numerical solutions are in excellent agreement with experimental data. An analytical study based on the Weisskopf-Wigner approximation gives physical insight into the transient optical nonlinearities of semiconductor microcavites. It is able to explain the physical origin of the unusual transient shifts and asymmetricexcitation-induced dephasing observed experimentally. this theory demonstrates that the nonperturbative regime provides a unique tool for measuring the spectrum of four-particle correlations.Salvatore SavastaOmar Di StefanoRaffaello Girlanda2005-05-31Z2010-04-13T11:20:20Zhttp://cab.unime.it/mus/id/eprint/326This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/3262005-05-31ZTransiet optical stark shift and excitation induced dephasing in the non-perturbative regimeWe show that the exciton-exciton scattering continuum has a significant influence on the transient non-linear optical response of semiconductor microcavities. Comparison between transient shifts observed in pump and probe experiments and calculations demonstrates almost complete cancellation between mean-field and two-exciton continuum contributions. Moreover, we show that suppression of non-linear absorption of the lower polariton observed in many experiments is determined by the specific spectral shape of these correlations. In particular, we find that the pump induced dephasing of polariton resonances is proportional to the spectrum of four-particle correlations calculated at the energy sum of the pumped and probed polaritons.Salvatore SavastaOmar Di StefanoRaffaello Girlanda2005-05-31Z2010-04-13T11:20:22Zhttp://cab.unime.it/mus/id/eprint/327This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/3272005-05-31ZThe effect of the exciton continuum on the exciton-exciton correlationWe present a numeric calculation of the exciton-exciton correlation for a one-dimensional semiconductor model with long-range Coulomb interactions, taking into account the effect of the effect of the exciton continuum. we use the obtained correlation functions to calculate the time integrated intensity of the four wave mixing signal. Changing the central frequency of the exciting pulses we observe changes in the profile and in the rise time of the time integrated signal for negative delays in qualitative agreement with experimental results. Our results show theoretically how the exciton continuum affects the coherence of four-particle correlations.Giovanna MartinoSalvatore SavastaRaffaello Girlanda2005-05-31Z2010-04-13T11:20:16Zhttp://cab.unime.it/mus/id/eprint/328This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/3282005-05-31ZPropagation of nonclassical light through a semiconductor microcavityWe extend recently developed schemes for field quantization in absorbing dielectric media with local susceptibilities to dielectric systems described by a nonlocal susceptibility, in order to quantize the electromagnetic field in quantum wells embedded in planar semiconductor microcavities. As an application of the formalism, we analyze the effects of the propagation through a semiconductor microcavity on a continuous-mode squeezed coherent state. In particular, we calculate the varince of the field trasmitted through the microcavity in the case of strong coupling regime for different detection schemes, as a function of the detuning, the exciton-photon coupling and the exciton homogeneous broadeningOmar Di StefanoSalvatore SavastaRaffaello Girlanda2005-05-31Z2010-04-13T09:39:16Zhttp://cab.unime.it/mus/id/eprint/329This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/3292005-05-31ZThe particle-photon interaction in systems descrided by model hamiltonians in second quantizationA simple replacement rule which allows the direct formulation in second quantization of the particle-photon interaction Hamiltonian in the velocity gauge is presented. We show that a transformation of the creation and annihilation operators of the particle Hamiltonian gives the interaction Hamiltonian. The rule is valid for both local and nonlocal Hamiltonian and gives the correct expression of the photon self-interaction term A2 also when only a projection of the particle Hamiltonian is taken into account. As an example the replacement rule is applied to the exciton operators in order to derive the polariton HamiltonianSalvatore SavastaRaffaello Girlanda2005-05-31Z2012-09-20T08:43:49Zhttp://cab.unime.it/mus/id/eprint/323This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/3232005-05-31ZMicroscopic theory of spatially resolved photoluminescence in quantum structuresWe present a microscopic quantum theory of spatially resolved photoluminescence in quantum wells with interface fluctuations. The theory can model low-temperature photoluminescence and photoluminescence excitation experiments performed in illumination, collection,illumination-collection mode or diffusion experiments where the spatial positions of excitation and collection are scanned independently. Numerically calculated two-dimensional images clarify the impact of the microscope setup on the obtained images and resolutions.Giuseppe PistoneSalvatore SavastaOmar Di StefanoRaffaello Girlanda2005-05-30Z2010-04-13T11:20:51Zhttp://cab.unime.it/mus/id/eprint/307This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/3072005-05-30ZThe influence of four-particle correlations on the parametric polariton amplificationWe present a microscopic theory of parametric polariton amplification in semiconductor microcavities including the influence of exciton-exciton correlations beyond mean-field. The complexity induced by the Coulomb interaction between electrons determines the noninstantaneous character of exciton-exciton collisions. We find that the observed great enhancement of gain when increasing the polariton splitting origins from the unique interplay of the noninstantaneous nature of exciton-exciton interactions with the strong coupling regime giving rise to polaritons.
Salvatore SavastaOmar Di StefanoRaffaello Girlanda2005-05-30Z2010-04-13T11:20:55Zhttp://cab.unime.it/mus/id/eprint/309This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/3092005-05-30ZImaging the wavefunctions of a quantum dot systemWe describe how, exploiting the current scanning near-field optical techniques, it is possible to map phase and modulus of the wavefunctions of a quantum dot system. In particular we propose an experimental setup based on an interferometric technique able to measure simultaneously modulus and phase of wavefunctions. We present numerical calculations simulating the measurements on dots arising from interface fluctuations of GaAs quantum wells.Omar Di StefanoSalvatore SavastaGiovanna MartinoRaffaello Girlanda2005-05-30Z2010-04-13T11:20:48Zhttp://cab.unime.it/mus/id/eprint/313This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/3132005-05-30ZTheory of Transient Optical Nonlinearities in Semiconductor MicrocavitiesWe present a theory of ultrafast time-resolved nonlinear spectroscopy in semiconductor microcavitiesincluding the influence of many-body and correlation effects beyond mean-field calculations. The theory,in close agreement with a number of experimental results, shows that semiconductor microcavities provide aunique tool for measuring the spectrum of four-particle correlations. We apply the theory to analyze the polaritonparametric amplification in semiconductor microcavities. The obtained results demonstrate that exciton exciton collisions can be controlled and engineered to produce almost decoherence-free collisions for the realizationof completely optical microscopic devicesRaffaello GirlandaSalvatore Savasta2005-05-30Z2010-04-13T11:20:38Zhttp://cab.unime.it/mus/id/eprint/314This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/3142005-05-30ZBiphotons from BiexcitonsWe analyze the spontaneous and stimulated optical decay of states with two electron-hole pairs virtually excited by optical pumping. We find that the photon pairs from the spontaneous fission in bulk large-gap semiconductors and in semiconductor microcavities exhibit quantum features which can be observed by coincidence detection.Salvatore SavastaGiovanna MartinoOmar Di StefanoRaffaello Girlanda2005-05-30Z2010-04-13T11:20:41Zhttp://cab.unime.it/mus/id/eprint/315This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/3152005-05-30ZCoherence and correlation in semiconductor microcavitiesWe present an overview of our results concerning the influence of two-pair continuum coherences on the transient nonlinear optical response of semiconductor microcavities. We show that the interplay between these 4-particle coherences and the nonperturbative light-matter interaction produces highly desirable almost decoherence-free exciton-exciton collisions on the lower polariton branch. This effect gives rise to the very different nonlinear absorption rates on the two polariton branches observed in many experiments and make possible to reach a very high degree of amplification in samples with large Rabi splitting. Moreover, we show that the availability of almost decoherence free exciton-exciton collisions can be used for the realization of coherent trapping of polariton emission and amplification. This coherent manipulation and trapping of many-particle polariton states can be performed employing both ultrafast and continuous wave operation.Omar Di StefanoSalvatore SavastaRaffaello Girlanda2005-05-30Z2010-04-13T11:20:41Zhttp://cab.unime.it/mus/id/eprint/316This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/3162005-05-30ZEntangled photon pairs from the optical decay of biexcitonsWe show that it is possible to transfer the exciton-exciton Coulomb correlation to photons, producing thus pairs of near-gap photons with a high degree of quantum entanglement. The photon pairs emerge from the spontaneous optical decay of biexcitons into two polaritons. The pair intensity-correlations, calculated in the low density limit for a CuCl slab, exhibit quantum features which can be observed by coincidence detection.Salvatore SavastaGiovanna MartinoRaffaello Girlanda2005-05-30Z2010-04-13T11:20:32Zhttp://cab.unime.it/mus/id/eprint/317This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/3172005-05-30ZMicroscopic calculation of noise current operators for electromagnetic field quantization in absorbing material systems.We present a microscopic quantization scheme for the electromagnetic field in dispersive and lossy dieletrics of arbitrary geometry. This method also describes anisotropic media and media driven by ligth field via a spatially nonlocal permittivity. The method removes the need for complicated diagonalization of material, reservoir and field variables and allows us to include the effect of all the material excitations. Dissipation inside the medium is described by considering the coupling of the polarization quanta of the system with the reservoir oscillators in the usual Langevin approach. Omar Di StefanoSalvatore SavastaRaffaello Girlanda2005-05-30Z2012-09-20T08:44:38Zhttp://cab.unime.it/mus/id/eprint/318This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/3182005-05-30ZSpatially resolved spectra in semiconductor quantum structures: spatially averaged spectra compared to far-field spectra. The optical spectra of homogeneous surface systems can display remarkable differences in the near and far zones. The spectral changes occur due to the loss of evanescent modes in the far zone. These changes clearly show that near-field optical spectroscopy, besides resolving nanometric structures give also access to excitations that cannot be revealed in the far zone. Are these spectral changes detectable in real systems affected by disorder and imperfections? We address this issue by presenting a theoretical analysis of the local optical properties of semiconductor quantum wells including the effects of interface fluctuations. In particular we compare the far-field absorption spectrum with spatially averaged absorption spectra calculaded at different spatial resolutions. We find that summing up local optical spectra does not reproduce the global spectrum in contrast to findings at diffraction-limited resolutions. Giuseppe PistoneSalvatore SavastaOmar Di StefanoRaffaello Girlanda2005-05-27Z2010-04-13T11:20:43Zhttp://cab.unime.it/mus/id/eprint/311This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/3112005-05-27ZThree-dimensional quantum-optical input-output relations for arbitrary planar dielectricsWe present a three-dimensional quantum theory of light scattering, absorption, and emission in arbitrary planar dielectric systems. The theory is based on a scheme for quantization of the electromagnetic field in dispersive and lossy arbitrary planar dielectrics that takes explicitly into account the finite extent of the medium. We present general quantum-optical input-output relations of the output TE and TM photon operators to the corresponding input photon operators and to the reservoir noise operators. These three-dimensional input-output relations are uniquely determined by knowledge of the classical light modes of the planar dielectric structure. Salvatore SavastaOmar Di StefanoRaffaello Girlanda2005-05-27Z2010-04-13T11:20:46Zhttp://cab.unime.it/mus/id/eprint/312This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/3122005-05-27ZSignatures of the electromagnetic field quantization in the nonlinear optical response of excitonsWe present a fully quantum mechanical theory for an interacting system of photonsand Coulomb correlated electrons and holes in a semiconductor, using a pertubation series in theexciting laser field. The theory provides microscopic descriptions of nonlinear optical processes insemiconductors related to the electromagnetic field quantization. As an application of the theorywe show that it is possible to transfer the exciton exciton Coulomb correlation to photons, thusproducing pairs of near-gap photons with a high degree of quantum entanglement. The photon pairsemerge from the spontaneous optical decay of biexcitons into two polaritons. The pair intensitycorrelations, calculated in the lowdensity limit for a CuCl slab and for semiconductor microcavities,exhibit quantum features which can be observed by coincidence detection.Salvatore SavastaRaffaello Girlanda2005-05-25Z2010-04-13T09:39:06Zhttp://cab.unime.it/mus/id/eprint/287This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/2872005-05-25ZExciton-exciton correlation in the ultrafast nonlinear optical response in the nonperturbative regimeThe ultrafast nonlinear optical response of semiconductor-microcavities (SMCs) in the nonperturbative regime is attracting growing interest for exploring fundamental light-matter interactions in many-particle quantum systems, as well as for the future implementations of ultrafast photonic devices. In spite of many investigations, the coherent dynamics of excitonic nonlinear-response in the nonperturbative regime has not been fully understood. Open questions are how strong exciton-cavity coupling affects exciton-exciton (X-X) interactions, and how in turn the X-X correlation influences the nonlinear response of SmCs. We investigate these open questions and show that the nonperturbative regime provides an unprecedented tool for investigating four-particle correlations.We start from the equations for the third order exciton polarization and cavity field describing quantum optical effects and coherent nonlinear optics in SMCs, perform the semiclassical factorization and include multiple scattering processes. Salvatore SavastaOmar Di StefanoRaffaello Girlanda2005-05-25Z2012-09-20T08:42:43Zhttp://cab.unime.it/mus/id/eprint/288This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/2882005-05-25ZNear-field light emission from nano- and micrometric complex structuresWe propose a general theoretical scheme for the investigation of light emitted from nano- and micrometric structures of arbitrary shape and composition. More specifically, the proposed fully three-dimensional approach allows to derive the light-intensity distributions around the emitting structures and their modifications in the presence of nearby scattering objects. Our analysis allows to better identify the nontrivial relationship between near-field images and fluorescent objects.Marco PierucciniSalvatore SavastaRaffaello GirlandaR.C. IottiF. Rossi2005-05-25Z2013-01-22T10:48:23Zhttp://cab.unime.it/mus/id/eprint/291This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/2912005-05-25ZSilicon-based organic-inorganic microcavity and its dispersion curve from angle-resolved photoluminescence We report an experimental study of a planar organic-inorganic microcavity consisting of a porous silicon distributed Bragg reflector, a single layer of acridina orange as active material and a top aluminum reflector. By tuning the cavity resonance energy around the maximum of the organic material photoluminescence, we found an intense emission and a spectral narrowing of the emission band to about 45 meV. The angle-resolved photoluminescence spectra enable us to determine the microcavity dispersion curve. The very good agreement with the theoretical dispersion provides a precise determination of the refractive index of the organic material.A. ArenaS. A. PatanĂ¨G. SaittaSalvatore SavastaRaffaello GirlandaR. Rinaldi2005-05-25Z2010-04-13T11:21:24Zhttp://cab.unime.it/mus/id/eprint/292This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/2922005-05-25ZImaging spectroscopy of quantum wells with interfacial fluctuations: A theoretical description We present a theoretical approach for the simulation of scanning local optical spectroscopy in disordered quantum wells (QWs). After a single realization of the disorder potential, we calculate spectra on a mesh of points on the QW plane, thus obtaining a three-dimensional matrix of data from which we construct two-dimensional spectroscopic images of excitons laterally localized at interface fluctuations. Our simulations are in close agreement with the experimental findings, and contribute to the interpretation of spatially resolved spectra in QWs.Omar Di StefanoSalvatore SavastaGiovanna MartinoRaffaello Girlanda2005-05-25Z2010-04-13T11:21:17Zhttp://cab.unime.it/mus/id/eprint/297This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/2972005-05-25ZLight quantization for arbitrary scattering systemsWe present a quantum theory of light scattering for the analysis of the quantum statistical and fluctuation properties of light scattered or emitted by micrometric and nanometric three-dimensional structures of arbitrary shape. We obtain general three-dimensional quantum-optical input-output relations providing the output photon operators in terms of the input photon operators and of the noise currents of the scattering system. These relations hold also for photon operators associated with evanescent fields, for anisotropic scattering systems and/or for media with a nonlocal susceptibility. We find that the commutation relations of the output photon operators, carrying all the information on the scattering and/or the emission process, result to be fixed by energy conservation and reciprocity. We prove that this quantization scheme is consistent with QED commutation rules by using a novel relationship between vacuum and thermal fluctuations. This theoretical framework has been applied to analyze the spectral density of light close to a point scatterer under different nonequilibrium conditionsSalvatore SavastaOmar Di StefanoRaffaello Girlanda2005-05-25Z2010-04-13T11:21:09Zhttp://cab.unime.it/mus/id/eprint/298This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/2982005-05-25ZTheory of local optical spectroscopy of quantum wires with interface fluctuationsWe present a theory of local optical spectroscopy in quantum wires taking into account structural disorder. The calculated spatially resolved spectra show the individual spectral lines due to the exciton states localized by the disordered potential in agreement with experimental findings.We investigate systematically the influence of the potential profile and of the spatial resolution on the local optical spectra. Several line scans along the wire axis are obtained for different spatial correlations and strength of the disorder potential and for different spatial resolutions ranging from the subwavelength to the diffraction limit. Lowering the spatial resolution causes the disappearance of many spectral lines due to destructive spatial interference. However, our results show that information on the individual eigenstates of this quasi one-dimensional quantum system can be obtained at also resolutions significantly lower than the correlation length of interface fluctuations. Omar Di StefanoSalvatore SavastaRaffaello Girlanda2005-05-25Z2010-04-13T11:21:10Zhttp://cab.unime.it/mus/id/eprint/300This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/3002005-05-25ZQuantum theory of light scattering for arbitrary finite size dieletric and conducting structuresWe present a quantum theory of ligth scattering for the analysis of the quantum statistical and fluctuation properties of light scattered or emitted by micrometric and nanometric three dimensional structures of arbitrary shape. This theory provides a general and unified basis for analysing a large class of optical processe where quantum and or thermal fluctuations play a role. Salvatore SavastaOmar Di StefanoRaffaello Girlanda2005-05-25Z2010-04-13T11:21:12Zhttp://cab.unime.it/mus/id/eprint/301This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/3012005-05-25ZThe influence of two-exciton correlations on the dynamics of parametric polariton amplificationWe present an overview of our results concerning the influence of two-pair continuum coherences onthe transient nonlinear optical response of semiconductor microcavities. We show that the interplaybetween these 4-particle coherences and the nonperturbative light-matter interaction produces highlydesirable almost decoherence-free exciton-exciton collisions on the lower polariton branch. This effectgives rise to the very different nonlinear absorption rates on the two polariton branches observed inmany experiments and make possible to reach a very-high degree of amplification in samples withlarge Rabi splitting.Omar Di StefanoSalvatore SavastaRaffaello Girlanda2005-05-25Z2012-09-20T08:44:24Zhttp://cab.unime.it/mus/id/eprint/303This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/3032005-05-25ZIs the spatially averaged spectrum equal to the global spectrum?Near-field optical spectroscopy and microscopy give access to excitations that cannot be revealed in the far zone. In order to investigate these remarkable differences, we present a theoretical analysis of the local optical properties of semiconductor quantum wells including the effects of disorder arising from interface fluctuations. The far-field absorption spectrum is compared with spatially averaged absorption spectra calculated at different spatial resolutions. We find that summing up local optical spectra does not reproduce the global spectrum in contrast to findings at diffraction-limited resolutions.Giuseppe PistoneOmar Di StefanoSalvatore SavastaRaffaello Girlanda2005-05-25Z2013-01-22T10:47:57Zhttp://cab.unime.it/mus/id/eprint/294This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/2942005-05-25ZPhotoluminescence from a soluble semiconducting polymer in waveguide and microcavity configurationsThe optical properties of thin films of PVK-Alq3 are examined by means of spectrophotometry in the UV-VIS-NIR. Photoluminescence (PL) measurements indicate that the polymer films deposited on glass substrates behave as asymmetrical planar waveguides for the emitted light. The waveguided luminescence shrinks and change color with respect to the non-waveguided emission. Stronger changes in the luminescence features are observed using a microcavity configuration, obtained by spin-coating PVK-Alq3 on an inorganic Distributed Bragg Reflector (DBR) and by vacuum-depositing a thick aluminum layer on the top of the polymer film. M. AllegriniA. ArenaM. LabardiGiovanna MartinoRaffaello GirlandaC. PaceS. A. PatanĂ¨G. SaittaSalvatore Savasta2005-05-25Z2012-09-20T08:44:00Zhttp://cab.unime.it/mus/id/eprint/302This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/3022005-05-25ZSpatially resolved photoluminescence in semiconductor nanostructures: A theoretical descriptionWe present a microscopic quantum theory of spatially resolved photoluminescence in quantum wells with interface fluctuations that includes light quantization, acustic phonon scattering, and inhomogeneous sample-excitation and/or light-detection. The theory can model low-temperature photoluminescence and photoluminescence excitation experiments performed in illumination, collection or illumination-collection mode or diffusion experiments where the spatial positions of excitation and collection are scanned independently. Numerically calculated two-dimensional images agree with images from near-field photoluminescence experiments and put forward the potentials of the method for the understanding of near-field light emission from semiconductor quantum structures.Giuseppe PistoneSalvatore SavastaOmar Di StefanoRaffaello Girlanda2005-05-25Z2012-09-20T08:43:38Zhttp://cab.unime.it/mus/id/eprint/293This item is in the repository with the URL: http://cab.unime.it/mus/id/eprint/2932005-05-25ZMicroscopic quantum theory of spatially resolved photoluminescence in semiconductor quantum structuresWe present a microscopic analysis of spatially resolved photoluminescence and photoluminescence excitation spectroscopy in semiconductor quantum structures. Such theoretical and numerical framework provides a general basis for the description of spectroscopic imaging in which the excitation and detection energies and spatial positions can all independently be scanned. The numerical results clarify the impact of the near-field optical setup on the obtained images and resolutions.Giuseppe PistoneSalvatore SavastaOmar Di StefanoRaffaello Girlanda