Publications (7)15.58 Total impact
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Article: Evidence of “crossed” transitions in dots-in-a-well structures through waveguide absorption measurements
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ABSTRACT: In-plane absorption measurements were performed at room temperature by means of a waveguide transmission setup on a Stranski–Krastanov InAs dots-in-a-well system emitting at 1.3 μm embedded in a p-i-n structure. The polarization dependence of quantum dot (QD) absorption was exploited to resolve its discrete and continuous spectral components and study them separately under reverse bias application. The quantum confined Stark effect observed in the discrete spectral component gave evidence of an upward built-in QD dipole of about 9.5×10−29 C m. The continuous component was found to originate from electronic transitions involving a QD state and a quantum well state.Applied Physics Letters 10/2008; 93(15):151112-151112-3. · 3.84 Impact Factor -
Article: Enhanced Performances of Quantum Dot Lasers Operating at 1.3 m
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ABSTRACT: Due to their delta-like density of states, quantum dots (QDs) were expected to improve laser device performances with respect to quantum wells (QWs). Nevertheless, some important drawbacks limit this technology. For instance, QD laser still suffers from a low value of the modal gain, due to the low areal density of QDs, and inhomogeneous broadening, especially when multistacked layers are used. In this paper, we demonstrate that a linear increase of the QD modal gain with the QD layers number, as typically achieved in multi-QW lasers, is possible by a careful control of the Stranski-Krastanov QDs growth and QDs stacking optimization. A low-transparency current density of 10 A/cm<sup>2</sup> per QD layer and a modal gain of 6 cm<sup>-1</sup> per QD layer were achieved from laser structures containing up to seven QD layers. We demonstrate 10-Gb/s direct modulation (until a temperature of 50 <sup>deg</sup>C) and high T <sub>0</sub> (110 K) from a single-mode device containing six QD layers.IEEE Journal of Selected Topics in Quantum Electronics 08/2008; · 3.78 Impact Factor -
Article: Simultaneous filling of InAs quantum dot states from the GaAs barrier under nonresonant excitation
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ABSTRACT: The authors have performed time resolved photoluminescence measurements by upconversion technique on InAs quantum dots embedded in an InGaAs/GaAs quantum well emitting at 1.3 μm at room temperature. A detailed analysis of the photoluminescence transients as a function of the excitation density and for different detection energies between the quantum dot transitions and the GaAs absorption edge shows that the intradot relaxation is slower than the direct carrier capture from the barrier states through a continuum background relaxation.Applied Physics Letters 03/2007; 90(11):111907-111907-3. · 3.84 Impact Factor -
Article: High‐gain low‐threshold InAs/InGaAs/GaAs quantum dot lasers emitting around 1300 nm
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ABSTRACT: Three semiconductor laser structures containing 1, 3 and 5 layers of self organized InAs/InGaAs/GaAs quantum dots (QDs) have been grown by Molecular Beam Epitaxy. Broad area lasers were processed from the grown wafers and tested. These structures show a linear increase of the modal gain with the number of QDs layers with an average modal gain per QDs layer of ∼5 cm–1. A maximum modal gain of 25 cm–1 was obtained at room temperature (RT) from the sample containing 5 layers of QDs. A transparency current density and a low internal loss value of ∼5.5 A/cm2 per QD layer and 1.5 cm–1 were deduced respectively. For an infinite cavity length a minimum threshold current density of ∼9 A/cm2 per QD layer was inferred. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)physica status solidi (c) 11/2006; 3(11):4027 - 4030. -
Article: High-modal gain 1300-nm In(Ga)As-GaAs quantum-dot lasers
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ABSTRACT: A semiconductor laser containing seven InAs-InGaAs stacked quantum-dot (QD) layers was grown by molecular beam epitaxy. Shallow mesa ridge-waveguide lasers with stripe width of 120 mum were fabricated and tested. A high modal gain of 41 cm<sup>-1</sup> was obtained at room temperature corresponding to a modal gain of ~6 cm<sup>-1</sup> per QD layer, which is very promising to enable the realization of 1.3-mum ultrashort cavity devices such as vertical-cavity surface-emitting lasers. Ground state laser action was achieved for a 360-mum-cavity length with as-cleaved facets. The transparency current density per QD layer and internal quantum efficiency were 13 A/cm<sup>2</sup> and 67%, respectivelyIEEE Photonics Technology Letters 09/2006; · 2.19 Impact Factor -
Article: An experimental setup for room temperature waveguide spectroscopy of self-assembled quantum dots
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ABSTRACT: In this work we present the realization of an experimental setup to measure the absorption spectrum of low planar density active media in nanoscale devices. The experimental technique employs in-plane light transmission through a waveguide embedding the active medium. It has been applied to the investigation of the room temperature optical properties of low density self-assembled InGaAs/GaAs quantum dots (QDs), emitting around 1.3 µm. A detailed analysis of the obtained spectra showed the occurrence of a Stokes shift which after inspection turned out to be related to the thermally activated carrier migration throughout the QD ensemble.Journal of Optics A Pure and Applied Optics 06/2006; 8(7):S514. · 1.92 Impact Factor -
Article: Rapid prototyping of two-dimensional photonic crystal devices by a dual beam focused ion beam system
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ABSTRACT: We report on the fabrication of two-dimensional photonic crystals (2D-PC) structures by means of a focused ion beam (FIB), which is an alternative process well suited for the fast prototyping of high quality 2D-PC devices. Through FIB process the removal of materials is achieved without the use of a patterned resist mask. We have fabricated two different short in-plane cavities: the ridge geometry configuration, obtained through trenches etched down to the bottom cladding by means of a FIB process, and a second identical cavity terminated by a 2D-PC back mirror consisting of a triangular lattice of air holes in GaAs slab. Both the ridge cavity and the photonic crystal cavity have been optically characterized by detecting their edge-emitted photoluminescence. As expected, by virtue of its higher back mirror reflectivity leading to lower cavity losses, the 2D-PC cavity shows the occurrence of amplified spontaneous emission at an excitation power density three times lower than in the standard ridge cavity.Microelectronic Engineering.
Top Journals
Institutions
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2006
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National Research Council
Roma, Latium, Italy -
Université de Montpellier 2
Montpellier, Languedoc-Roussillon, France
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