47 research outputs found
Delay and distortion of slow light pulses by excitons in ZnO
No full textistortion of light pulses in ZnO caused by both bound and free excitons is demonstrated by time-of-flight spectroscopy. Numerous lines of bound excitons dissect the pulse spectrum and induce slowdown of light propagation around the dips. Exciton-polariton resonances determine the overall pulse delay, which approaches 1.6 ns at 3.374 eV for a 0.3 mm propagation length, as well as the pulse curvature in the time-energy plane and its attenuation. Analysis of cw and time-resolved data yields the excitonic parameters inherent for bulk ZnO. A discrepancy is found between these bulk parameters and those given by surface-probing techniques.Original Publication:T V Shubina, M M Glazov, N A Gippius, A A Toropov, D Lagarde, P Disseix, J Leymarie, B Gil, Galia Pozina, J Peder Bergman and Bo Monemar, Delay and distortion of slow light pulses by excitons in ZnO, 2011, Physical Review B. Condensed Matter and Materials Physics, (84), 7, 075202.http://dx.doi.org/10.1103/PhysRevB.84.075202Copyright: American Physical Societyhttp://www.aps.org
Potentialities of GaN-based microcavities in strong coupling regime at room temperature.
No full textIn a recent publication [N. Antoine-Vincent, F. Natali, D. Byrne, A. Vasson, P. Disseix, J. Leymarie, M. Leroux, F. Semond, J. Massies, Phys. Rev. B 68 (2003) 153313], we have highlighted for the first time the exciton–photon strong coupling in a GaN-based microcavity and obtained a Rabi splitting of 31 meV persistent at 77 K. Our aim is now to study the feasibility of GaN-based microcavities for which the strong coupling regime would be maintained at room temperature. A complex heterostructure containing GaN/AlGaN quantum wells (QWs) is investigated by photoreflectivity and reflectivity at 5 K. The QW thickness is 3 nm and the Al composition and thickness of the barriers are respectively 0.11 and 10 nm. From the modeling of the experimental spectra, the values of the oscillator strength, the energy and the broadening parameter of the QW fundamental transition are determined; the broadening is found to be relatively weak (15 meV). Simulations of microcavities containing QWs have then been performed including this set of parameters: a theoretical Rabi splitting of 34 meV is obtained at 5 K. Considering an additional broadening induced by the increase of the temperature (23 meV), the strong coupling regime could be maintained theoretically at room temperature in such a structure. This is due to the low value of the inhomogeneous broadening related to the QW transition which is lower than in bulk GaN. The influence of the QW number and the nature of the Bragg mirror on the Rabi splitting is then discussed in realistic structures
Thermally detected optical absorption, reflectance, and photoreflectance of In(As,P)/InP quantum wells grown by gas source molecular beam epitaxy
No full textThermally detected optical absorption, reflectance and photo-reflectance of In(As,P)/InP quantum wells grown by gas source molecular beam epitaxy
No full textOptical investigation of piezoelectric field effects on excitonic properties in (111)B-grown (In, Ga)As/GaAs quantum wells
No full textEffect of indium surface segregation on excitonic properties in (111)B-grown (In,Ga)As/GaAs multiple quantum wells
No full textOptical properties of (In,Ga)As/GaAs heterostructures grown on conventional (100) and (111)B GaAs substrates
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Modelling of absorption and emission spectra of InxGa1-xN
No full textThermally detected optical absorption (TDOA) and photoluminescence (PL) experiments were performed at 0.35 and 4 K, respectively, on InxGa1-xN (0 < x < 0.12) layers grown on GaN-coated sapphire substrates by molecular beam epitaxy. By modelling the absorption spectra of (In,Ga)N and GaN it is possible to deduce the bandgap energy and absorption coefficient of the alloy. With the complex GaN refractive index, measured by ellipsometry, the inferences that appear in the TDOA spectra can be modelled. An approach is proposed to remove these oscillations which are also present in the PL spectra. (C) 2001 Elsevier Science B.V. All rights reserved.LASP
Modelling of thermally detected optical absorption and luminescence of (In,Ga)N/GaN heterostructures
No full textThermally detected optical absorption (TDOA) and photoluminescence (PL) experiments are performed at 0.35 and 4 K, respectively, on InxGa1-xN(x less than or equal to 0.12) layers grown on GaN by molecular beam epitaxy. The modelling of absorption allows us to extract the absorption coefficients and bandgap energies of (In,Ga)N alloy. A bowing parameter equal to 2.4 eV is deduced. The knowledge of the GaN complex refractive index, previously measured, enables us to account for the Fabry-Perot interferences which structure the TDOA and PL spectra. A procedure is proposed to remove the latter in the PL spectrum of nitride based heterostructures, The model is based on the description of the light propagation in an active layer sandwiched between two heterostructures. The parameters deduced from the absorption line shape adjustment are used to take the absorption and optical path into account in the different layers of the samples. (C) 2000 Elsevier Science Ltd. All rights reserved.LASP
