142 results on '"Alok Rudra"'
Search Results
102. 30°C CW operation of 1.52 [micro sign]m InGaAsP/AlGaAs vertical cavity lasers with in situ built-in lateral current confinement by localised fusion
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Isabelle Sagnes, Fabienne Gaborit, Jean-Christophe Harmand, C.-A. Berseth, Elyahou Kapon, R. Raj, Joel Jacquet, C. Stark, J. Boucart, A. Syrbu, Alok Rudra, O. Dehaese, and V. Iakovlev
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In situ ,Fusion ,Materials science ,Threshold current ,Aperture ,business.industry ,Laser ,law.invention ,Optics ,law ,Optoelectronics ,Vertical cavity lasers ,Wafer ,Electrical and Electronic Engineering ,Current (fluid) ,business - Abstract
1.52 µm double fused InGaAsP/AlGaAs vertical cavity surface emitting lasers with in situ built-in lateral current confinement were fabricated using a localised wafer fusion process. A threshold current of 2.5 mA at 4 V was obtained for devices with a 10 × 10 µm2 current aperture. These devices operate CW up to 30°C. The width of the dominant mode is less than 0.1 nm and the sidemode suppression ratio is 30 dB.
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- 1998
103. Characteristics of InAsP/InGaAsP edge emitting laser diodes obtained by localised fusion on GaAs substrates
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Alok Rudra, C.-A. Berseth, Eli Kapon, V. Iakovlev, A. Syrbu, J Behrend, J.F. Carlin, Laurent Sagalowicz, and John E. Fernández
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chemical beam epitaxial growth ,gallium ,arsenide ,Materials science ,business.industry ,chemistry.chemical_element ,Laser ,Crystallographic defect ,Chemical beam epitaxy ,Semiconductor laser theory ,Arsenide ,law.invention ,surface emitting lasers ,chemistry.chemical_compound ,chemistry ,law ,Optoelectronics ,Electrical and Electronic Engineering ,Gallium ,business ,Quantum well ,Diode - Abstract
Chemical beam epitaxy (CBE) grown InAsP/InGaAsP edge-emitting laser diodes on GaAs substrates obtained by localised fusion in a nitrogen environment exhibit high quality fused interfaces. A degradation of fused lasers is observed which is attributed to the disordering of quantum wells at fusion temperatures induced by point defects incorporated during low temperature growth.
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- 1997
104. Erratum: ‘‘As/P interdiffusion in ultrathin InAs/InP strained quantum wells’’ [Appl. Phys. Lett. 65, 341 (1994)]
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H.-J. Bühlmann, Jean-François Carlin, Jean-Michel Sallese, Romuald Houdré, Seth T. Taylor, Marc Ilegems, and Alok Rudra
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Materials science ,Photoluminescence ,Physics and Astronomy (miscellaneous) ,Condensed matter physics ,Activation energy ,Quantum well - Abstract
The intermixing process of ultrathin InAs/InP strained quantum well structures by thermal annealing at 730–830 °C is investigated by photoluminescence measurements. Analyzing the results using a microscopic model, the interdiffusion process is characterized by an activation energy close to 3.8±0.2 eV, leading to an interdiffusion coefficient close to 7±0.5×10−17 cm2/s at 830 °C.
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- 1994
105. Oriented overgrowths in MOVPE-grown GaAs
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André Rocher, Pierre Gibart, Alok Rudra, J. C. Grenet, and Hélène Heral
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Diffraction ,Materials science ,business.industry ,Crystal structure ,Condensed Matter Physics ,Epitaxy ,Inorganic Chemistry ,Crystallography ,Transmission electron microscopy ,Materials Chemistry ,Optoelectronics ,Crystallite ,Metalorganic vapour phase epitaxy ,business ,Hillock ,Stacking fault - Abstract
The crystallographic structure of crater-containing oriented overgrowths on GaAs epitaxial layers grown by metalorganic vapor phase epitaxy (MOVPE) has been studied by transmission electron microscopy and diffraction. The craters are the visible outward sign of polycrystalline constructions of 6 grains or more having low order twin relations with the matrix. Anisotropic development of the facets of the grains is proposed to be the growth mechanism of the hillock. Stacking fault pyramids are present but their correlation with craters and overgrowths is not systematic.
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- 1988
106. Anisotropic Growth of GaAs in MOVPE
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J. C. Guillaume, Yves Monteil, Alok Rudra, Pierre Gibart, A. Tromson-Carli, and Claude Schiller
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Surface diffusion ,Materials science ,Hydrogen ,chemistry ,Chemical physics ,Desorption ,chemistry.chemical_element ,Metalorganic vapour phase epitaxy ,Growth rate ,Epitaxy ,Order of magnitude ,Dynamic equilibrium - Abstract
In chloride vapour phase epitaxy of GaAs, it is known that the growth velocity depends on the cr stallographic face. Two orders of magnitude_difference in growth rate could occur between {111}Ga and {111}Aa. SO far, these features are strongly supported by the analysis of orientational dependence of the growth rate associated with surface kinetics. It is assumed that a dynamic equilibrium between the growing surfaces and the gas phase occurs, and the rate limiting process was shown to be the desorption of chlorine via hydrogen at the steps (1).
- Published
- 1989
107. Quantitative Imaging of InGaAs/GaAs Layers Using Transmission Electron Microscopy Methods: Characterization of Stresses and Chemical Composition
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Pierre Stadelmann, Eli Kapon, Philippe A. Buffat, Klaus Leifer, Alok Rudra, and J. Cagnon
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Nanostructure ,business.industry ,Chemistry ,Heterojunction ,Condensed Matter Physics ,Characterization (materials science) ,Inorganic Chemistry ,Optics ,Residual stress ,Transmission electron microscopy ,Quantum dot ,Materials Chemistry ,business ,Chemical composition ,Quantum well - Abstract
Reference LPN-ARTICLE-2002-003doi:10.1016/S0022-0248(01)02297-7View record in Web of Science Record created on 2008-02-29, modified on 2017-05-12
108. Optical studies of modulation-doped V-groove quantum wires: Fermi-edge singularity
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Alok Rudra, D. Y. Oberli, and Eli Kapon
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Physics ,Electron density ,Photoluminescence ,Absorption spectroscopy ,Condensed matter physics ,business.industry ,Doping ,Resonance ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,Condensed Matter Physics ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,Singularity ,Semiconductor ,business ,Quantum - Abstract
We report on an experimental study of the optical properties of modulation-doped V-groove semiconductor quantum wires. The Fermi-edge singularity is observed in emission and only weakly in absorption spectra. The conditions necessary for its observation are assessed by varying the electron density and providing the occupation of one, two or three one-dimensional (1D) subbands. We show that the existence of a strong optical singularity is related to both the effect of the hole localization and that of an enhancement induced by Coulomb correlations with a resonance associated with a partially empty 1D subband.
109. Parabolic tailored-potential quantum-wires grown in inverted pyramids
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Karl Fredrik Karlsson, M. Lazarev, Eli Kapon, J. Szeszko, and Alok Rudra
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Photoluminescence ,Nanostructure ,Materials science ,business.industry ,Patterned growth ,Quantum wires ,Heterojunction ,Condensed Matter Physics ,Epitaxy ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,Inorganic Chemistry ,MOVPE ,Low dimensional semiconductors ,Condensed Matter::Materials Science ,Materials Chemistry ,Optoelectronics ,Heterostructures ,Metalorganic vapour phase epitaxy ,business ,Spectroscopy ,Quantum ,Curse of dimensionality - Abstract
Quasi-one-dimensional AlGaAs quantum wires (QWRs) with parabolic heterostructure profiles along their axis were fabricated using metallorganic vapor phase epitaxy (MOVPE) On patterned (111)B GaAs substrates. Tailoring of the confined electronic states via modification in the parabolic potential profile is demonstrated using model calculations and photoluminescence spectroscopy. These novel nanostructures are useful for studying the optical properties of systems with dimensionality between zero and one. (C) 2014 Elsevier B.V. All rights reserved.
110. Site-controlled InGaAs/GaAs pyramidal quantum dots grown by MOVPE on patterned substrates using triethylgallium
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Alok Rudra, Eli Kapon, Benjamin Dwir, Pascal Gallo, C. Jarlov, A. Lyasota, and B. Rigal
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Materials science ,Fabrication ,Ingaas gaas ,business.industry ,Quantum dots ,TMGa ,Nanotechnology ,Condensed Matter Physics ,TEGa ,Inorganic Chemistry ,MOVPE ,chemistry.chemical_compound ,chemistry ,Quantum dot ,MOCVD ,Materials Chemistry ,Optoelectronics ,Pyramidal quantum dots ,Metalorganic vapour phase epitaxy ,Triethylgallium ,Trimethylgallium ,business - Abstract
The fabrication and characterization of site-controlled InGaAs/GaAs quantum dots (QDs) made by MOVPE using triethylgallium (TEGa) on patterned {111}B GaAs substrates are reported. Results are compared to more traditional pyramidal QD structures grown employing trimethylgallium (TMGa). Several potential advantages of the use of TEGa are demonstrated, including more reproducible achievement of QD transitions with narrow (< 100 mu eV) linewidths and better spectral uniformity across patterned substrates. These features are important for QD integration in optical cavities, which require both site and spectral stringent control. (C) 2014 Elsevier B.V. All rights reserved.
111. Magneto-photoluminescence of heavy- and light-hole excitons in site-controlled pyramidal quantum dots
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Emanuele Pelucchi, M. Byszewski, D. Y. Oberli, B. Chalupar, Alok Rudra, Karl Fredrik Karlsson, and Eli Kapon
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Physics ,exciton ,Photoluminescence ,Quantitative Biology::Neurons and Cognition ,Condensed matter physics ,Condensed Matter::Other ,g factor ,Exciton ,quantum dot ,magnetic field ,Light hole ,Condensed Matter Physics ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,Wires ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,Magnetic field ,Condensed Matter::Materials Science ,Quantum dot ,confinement ,Physics::Atomic Physics ,Magneto - Abstract
Pyramidal, site-controlled InGaAs/AlGaAs quantum dots (QDs) are studied by micro-photoluminescence (PL) spectroscopy in a magnetic field. The light-hole (LH) excitonic transitions exhibit diamagnetic shifts similar to those of their heavy-hole (HH) counterparts. From the evolution of the excitonic lines, effective g-factors of g = 1.7 and 0.4 for HH and LH neutral excitons are inferred. (c) 2007 Elsevier B.V. All rights reserved.
112. Observation of Stimulated Emission and Lasing in Quantum-wire Photonic-crystal Nanocavities
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Pascal Gallo, Eli Kapon, Benjamin Dwir, K.A. Atlasov, Karl Fredrik Karlsson, and Alok Rudra
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Materials science ,business.industry ,Quantum wire ,Physics::Optics ,Gain-switching ,Semiconductor ,Optoelectronics ,Spontaneous emission ,Stimulated emission ,Photonics ,business ,Lasing threshold ,Microcavity Lasers ,Photonic crystal - Abstract
Low-threshold lasing is experimentally achieved for the first time in semiconductor photonic-crystal nanocavities embedding site-controlled quantum wires. The effect is established via direct observation of the stimulated emission in the time domain.
113. Chemical Beam Epitaxy and Photoluminescence Characteristics of Ingaasp/Inp Braqwet Modulators
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F. K. Reinhart, M. Glick, Benjamin Dwir, M.-A. Dupertuis, R. Monnard, Alok Rudra, and Jean-François Carlin
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Materials science ,Photoluminescence ,business.industry ,Mechanical Engineering ,Inorganic chemistry ,Biasing ,Condensed Matter Physics ,Epitaxy ,QUANTUM-WELL STRUCTURES ,Chemical beam epitaxy ,Mechanics of Materials ,Rectangular potential barrier ,Optoelectronics ,GROWTH ,General Materials Science ,CBE ,Emission spectrum ,business ,Quantum well ,Molecular beam epitaxy - Abstract
We report on the growth of barrier, reservoir and quantum well electron transfer (BRAQWET) structures using chemical beam epitaxy. The photoluminescence spectra of the structures are affected by the bias voltage. The QW emission line is extinguished at positive bias and the barrier emission line is extinguished at negative bias. These effects might be used for the BRAQWETs characterization.
114. Engineering conduction and valence band states in site-controlled pyramidal quantum dots
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Pascal Gallo, Alok Rudra, Elyahou Kapon, Marco Felici, Arun Mohan, Jérôme Faist, and Benjamin Dwir
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Photon ,Physics and Astronomy (miscellaneous) ,business.industry ,Chemistry ,Band gap ,Condensed Matter::Other ,Photodetector ,Physics::Optics ,Polarization (waves) ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,Wires ,Semimetal ,Gallium arsenide ,Absorption ,Emission ,chemistry.chemical_compound ,Condensed Matter::Materials Science ,Cascade ,Quantum dot ,Fine-Structure ,Optoelectronics ,business ,Confinement - Abstract
We demonstrate engineering of carrier states in the conduction band (CB) and valence band (VB) of site-controlled InGaAs/GaAs quantum dots (QDs) grown into pyramidal recesses, by controlling their shape, size, and composition. QDs with CB level separation ranging from ∼15 to 70 meV are obtained, useful in applications based on intraband transitions, e.g., QD photodetectors and QD cascade lasers. Moreover, by varying the aspect ratio and composition of the QDs we are able to switch the polarization of the dominant interband transition, a feature of interest for producing single photon emitters and QD amplifiers with prescribed polarization states
115. Phonon-mediated exciton-photon coupling in site-controlled quantum-dot-nanocavity systems
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Alok Rudra, Giorgio Biasiol, Marco Felici, Benjamin Dwir, Lucia Sorba, Eli Kapon, Vincenzo Savona, M. Calic, Pascal Gallo, K.A. Atlasov, and Guillaume Tarel
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Coupling ,Physics ,Photon ,Condensed matter physics ,Condensed Matter::Other ,business.industry ,Phonon ,Exciton ,Cavity quantum electrodynamics ,Physics::Optics ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,Emission ,Quantum dot ,Photonics ,business ,Photonic crystal - Abstract
We show that far off-resonance exciton-photon coupling reported for self-assembled quantum dots in optical microcavities is not universal, and demonstrate that site-controlled dots exhibit clean phonon-mediated resonant coupling.
116. Single photon extraction and propagation in photonic crystal waveguides incorporating site-controlled quantum dots
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Eli Kapon, A. Lyasota, Irina Kulkova, Benjamin Dwir, Alok Rudra, and B. Rigal
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Coupling ,Physics ,Photon ,Physics and Astronomy (miscellaneous) ,business.industry ,Physics::Optics ,Ranging ,02 engineering and technology ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,021001 nanoscience & nanotechnology ,01 natural sciences ,Multiplexing ,Photonic crystal waveguides ,Quantum dot ,0103 physical sciences ,Coupling efficiency ,Optoelectronics ,010306 general physics ,0210 nano-technology ,business ,Photonic crystal - Abstract
Deterministic integration of site-controlled quantum dots with photonic crystal waveguides is demonstrated, which allows positioning the dots for optimal overlap with the waveguide modes. The coupling efficiency (β-factor) of quantum dot emission to propagating waveguide modes ranging from 0 to 88% is measured accounting for statistical variations of quantum dot properties. Using site controlled quantum dots permits us to distinguish between the spectral and spatial origins of fluctuations in β. The role of Fabry-Perot modes that prevent reaching a deterministic coupling between quantum dots and photonic crystal waveguides is revealed, and ways to overcome this problem are proposed. The results are useful for constructing high-flux single photon emitters based on multiplexed single photon sources.
117. Growth of GaInAs by chemical beam epitaxy
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Marc Ilegems, Jl Staehli, Alok Rudra, Jean-François Carlin, and Romuald Houdré
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Inorganic Chemistry ,Chemistry ,Semiconductor materials ,Materials Chemistry ,Analytical chemistry ,Mineralogy ,Condensed Matter Physics ,Chemical beam epitaxy - Abstract
Keywords: CRYSTALLOGRAPHIC PROPERTIES ; X-RAY ; INP ; INGAAS Note: Ecole polytech fed lausanne,inst appl phys,dept phys,ch-1015 lausanne,switzerland. Carlin, jf, ecole polytech fed lausanne,inst micro & optoelectr,dept phys,ch-1015 lausanne,switzerland.ISI Document Delivery No.: EY072Times Cited: 10Cited Reference Count: 11Cited References:ASONEN H, 1990, J CRYST GROWTH, V105, P101BASS SJ, 1986, J CRYST GROWTH, V79, P378BASSIGNANA IC, 1989, J APPL PHYS, V65, P4299FERRARI C, 1988, J APPL PHYS, V63, P2628GOETZ KH, 1983, J APPL PHYS, V54, P4543HALLIWELL MAG, 1984, J CRYST GROWTH, V68, P523KAWAGUCHI Y, 1986, 18TH C SOL STAT DEV, P619MACRANDER AT, 1987, J ELECTROCHEM SOC, V134, P1248MATSUI Y, 1985, J VAC SCI TECHNOL B, V3, P528RAZEGHI M, 1989, MOCVD CHALLENGE, V1TSANG WT, 1986, APPL PHYS LETT, V49, P170 Reference LOEQ-ARTICLE-1991-012doi:10.1016/0022-0248(91)90609-9 Record created on 2007-08-31, modified on 2017-05-12
118. Towards strong-coupling regime in singular site-controlled InGaAs quantum dots-nanocavities
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Benjamin Dwir, Chee Wei Wong, Alok Rudra, Eli Kapon, Wei Liu, Alessio Miranda, and Jiahui Huang
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Physics ,Quantum network ,Quantum beats ,Condensed matter physics ,Condensed Matter::Other ,Quantum dot laser ,Quantum dot ,Dephasing ,Cavity quantum electrodynamics ,Physics::Optics ,Quantum channel ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,Quantum - Abstract
We demonstrate the cavity quantum electrodynamics towards strong-coupling regime mediated by cavity loss and exciton pure dephasing in singular site-controlled quantum dot-nanocavity system, studied by micro-photoluminescence (μ-PL) and time-resolved PL (TRPL).
119. OMVPE Fabrication of Continuous Transitions between GaAs/AlGaAs Quantum Wells and V-Groove Quantum Wires
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D. Kaufman, Alok Rudra, Benjamin Dwir, S. Mautino, Eli Kapon, and F. Lelarge
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Fabrication ,Condensed matter physics ,Chemistry ,Monte Carlo method ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,Condensed Matter Physics ,Epitaxy ,Inorganic Chemistry ,Etching ,Materials Chemistry ,Thin film ,Quantum ,Quantum well ,Groove (music) - Abstract
The fabrication of defect-free and continuous transitions between AlGaAs/GaAs quantum wells (QWs) and quantum wires (QWRs) using organo-metallic vapor phase epitaxy on variable-width V-grooved substrates is demonstrated. The basic idea of our approach is developed using a Monte-Carlo simulation of the self-limiting growth on tapered grooves. A detailed surface and cross-sectional atomic force microscopy study reveals the high quality of the resulting coupled quantum structures. In particular, we demonstrate the efficient control, brought about by this experimental technique, on the well-wire transitions.
120. Conductance Quantization in V-Groove Quantum Wires
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Y. Berk, D. Kaufman, Alexander Palevski, Alok Rudra, Eli Kapon, and Benjamin Dwir
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Physics ,Quantization (physics) ,Condensed matter physics ,Quantum dot ,Ballistic conduction ,Quantum wire ,Conductance ,Conductance quantum ,Adiabatic process ,Quantum - Abstract
values of the conductance steps are suppressed. Our results suggest that a poor coupling between the 1D states of the wire and the 2D states of the reservoirs outside the gated region is responsible for the conductance suppression for strong lateral confinement. @S0163-1829~99!50516-X# In this paper we report the results of electron-transport measurements in V-groove GaAs/AlxGa12xAs quantum wires ~QWR's!. With these structures, it is possible to con- trol the strength of the lateral quantum confinement, thus allowing the comparison between nearly adiabatic and more abrupt transitions between the wire and the reservoir regions. In the ballistic transport regime, obtained for wires shorter than ;1.5 mm, we observe a systematic increase in the de- viation of the conductance steps from G 0 as the strength of the lateral confinement increases. Our data support recent models 7,9 assigning these deviations to electron scattering at
121. Strained V-groove quantum wires in multidimensional microcavities
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F. Lelarge, C. Constantin, Bruno Gayral, Alok Rudra, Jean-Michel Gérard, Eli Kapon, Klaus Leifer, and E. Martinet
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Physics ,Web of science ,Mechanics of Materials ,business.industry ,Mechanical Engineering ,Optoelectronics ,General Materials Science ,Condensed Matter Physics ,business ,Groove (engineering) ,Quantum - Abstract
Reference LPN-ARTICLE-2000-004doi:10.1016/S0921-5107(99)00553-XView record in Web of Science Record created on 2008-02-29, modified on 2017-05-12
122. The Role of Spin Polarization on the Quantum Hall Effect in 2DEG with Periodically Modulated Filling Factor
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Eli Kapon, Alok Rudra, M. Karpovski, V. J. Goldman, Alexander Palevski, A. Tsukernik, and Serge Luryi
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Physics ,Quantum spin Hall effect ,Condensed matter physics ,Web of science ,Spin polarization ,Filling factor ,Quantum mechanics ,Thermal Hall effect ,Spin Hall effect ,Quantum Hall effect ,Condensed Matter Physics ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials - Abstract
Reference LPN-ARTICLE-2002-007doi:10.1016/S1386-9477(01)00286-7View record in Web of Science Record created on 2008-02-29, modified on 2017-05-12
123. InGaAs/InGaAsP/InP Edge Emitting Laser Diodes on p-GaAs Substrates Obtained by Localised Wafer Fusion
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J.F. Carlin, Alok Rudra, John E. Fernández, C.-A. Berseth, A. Syrbu, Eli Kapon, and J Behrend
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Fusion ,Materials science ,Fabrication ,semiconductor junction lasers ,business.industry ,Wafer bonding ,1.55-MU-M WAVELENGTH LASERS ,INP ,FABRICATION ,Edge (geometry) ,Laser ,law.invention ,Optics ,law ,vertical cavity surface emitting lasers ,Optoelectronics ,Wafer ,Electrical and Electronic Engineering ,business ,Low voltage ,indium phosphide gallium arsenide ,Diode - Abstract
The authors present low voltage barrier p-InP/p-GaAs junctions obtained by localised fusion which facilitates a better evacuation of absorbed gases and native oxides from the fused interface. Using this approach InGaAs/lnGaAsP/InP edge emitting lasers fused to p-GaAs were realised for the first time, showing better parameters than as-grown diodes. The presented results prove that localised fusion is a suitable tool for achieving additional lateral current confinement, which may be important for a wide variety of other device applications.
124. Influence of strain and diffusion on the growth of V-groove InGaAs/GaAs quantum wires
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Klaus Leifer, F. Lelarge, Elyahou Kapon, Sven Stauss, and Alok Rudra
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Materials science ,Condensed matter physics ,Strain (chemistry) ,Ingaas gaas ,Diffusion (business) ,Quantum ,Groove (engineering)
125. Self-formation of hexagonal nanotemplates for growth of pyramidal quantum dots by metalorganic vapor phase epitaxy on patterned substrates
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Romain Carron, Alok Rudra, Pascal Gallo, Alessandro Surrente, Benjamin Dwir, and Eli Kapon
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hexagonal nanotemplates ,Materials science ,Nanotemplates ,Nanotechnology ,02 engineering and technology ,Epitaxy ,01 natural sciences ,Condensed Matter::Materials Science ,symmetry elevation ,Physics ,0103 physical sciences ,General Materials Science ,Kinetic Monte Carlo ,Electrical and Electronic Engineering ,010306 general physics ,kinetic Monte Carlo simulations ,Deposition (law) ,business.industry ,Hexagonal pyramid ,metalorganic vapor phase epitaxy ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Atomic and Molecular Physics, and Optics ,Symmetry (physics) ,epitaxial growth on patterned substrates ,Quantum dot ,Tetrahedron ,adatom diffusion ,Optoelectronics ,0210 nano-technology ,business ,Science, technology and society - Abstract
We demonstrate the self-formation of hexagonal nanotemplates on GaAs (111)B substrates patterned with arrays of inverted tetrahedral pyramids during metal-organic vapor phase epitaxy and its role in producing high-symmetry, site-controlled quantum dots (QDs). By combining atomic force microscopy measurements on progressively thicker GaAs epitaxial layers with kinetic Monte Carlo growth simulations, we demonstrate self-maintained symmetry elevation of the QD formation sites from three-fold to six-fold symmetry. This symmetry elevation stems from adatom fluxes directed towards the high-curvature sites of the template, resulting in the formation of a fully three-dimensional hexagonal template after the deposition of relatively thin GaAs layers. We identified the growth conditions for consistently achieving a hexagonal pyramid bottom, which are useful for producing high-symmetry QDs for efficient generation of entangled photons.
126. Semiconductor quantum-wires and nano-wires for optoelectronic applications
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Helge Weman, Bjørn-Ove Fimland, Alok Rudra, Jean-Christophe Harmand, Eli Kapon, S. Palmgren, D L Dheeraj, and Karl Fredrik Karlsson
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Photoluminescence ,Materials science ,Absorption spectroscopy ,business.industry ,Band gap ,Exciton ,Energy-Transfer ,Nanowire ,Growth ,Spectra ,Condensed Matter Physics ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,Molecular-Beam Epitaxy ,Optoelectronics ,Electrical and Electronic Engineering ,Wells ,business ,Absorption (electromagnetic radiation) ,Quantum well ,Molecular beam epitaxy - Abstract
Exciton transfer between two parallel GaAs V-groove quantum wires (QWRs) or two planar quantum wells (QWs) separated by AlGaAs barriers ranging from 5.5 nm to 20 nm thickness is studied by photoluminescence (PL) and PL excitation (PLE) spectroscopy. It is found that the transfer is strongly reduced between the widely spaced QWRs as compared with QWs. We have also investigated the optical absorption in single QWRs embedded in an AlGaAs V-shaped channel waveguide. Using a combination of PLE and absorption measurements we construct the full dependence of absorption spectra on the linear polarization. Our studies reveal the importance of inter-subband mixing in determining the energies of the light-hole-like transitions and thus the QWR absorption. Finally we present recent results on the fabrication and structural characterization of GaAs and GaP nanowires (NWs) grown by molecular beam epitaxy (MBE) on GaAs(111)B and Si(111) substrates, using Au-catalyzed vapor–liquid–solid growth technique. It is shown that, apart from optimizing the NW growth parameters, substrate material and the procedure for preparing the substrate before the MBE growth play an important role in controlling the NWs.
127. Wave-function splitting due to a two-dimensional quantum confined stark effect in quantum wires
- Author
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Helge Weman, M.-A. Dupertuis, Alok Rudra, E. Martinet, Elyahou Kapon, and Klaus Leifer
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Physics ,symbols.namesake ,Stark effect ,Condensed matter physics ,Oscillator strength ,Electric field ,Quantum-confined Stark effect ,symbols ,Electron ,Wave function ,Quantum ,Quantum well - Abstract
The quantum-confined Stark effect (QCSE) in one-dimensional (1D) structures is expected to display enhanced transfer of oscillator strength and enhanced Stark shifts compared with two-dimensional (2D) systems. 1D quantum wires (QWRs) are, however, characterized by a 2D confinement potential that may have important consequences: the QCSE thus becomes two dimensional (2D-QCSE). Here we report an experimental and theoretical investigation of the 2D-QCSE in V-groove QWRs. We observe the 2D-QCSE and find striking effects due to electron or hole wave-function splitting. Furthermore, interplay of electric field, geometry and valence band mixing gives rise to new tunable features in polarization anisotropy.
128. Polarization-entangled photons produced with high-symmetry site-controlled quantum dots
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Benjamin Dwir, Marco Felici, Jérôme Faist, Eli Kapon, Pascal Gallo, Alok Rudra, and Arun Mohan
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Physics ,Condensed matter physics ,Quantum sensor ,Cavity quantum electrodynamics ,Optical polarization ,Quantum Physics ,Quantum entanglement ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,Molecular physics ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,Condensed Matter::Materials Science ,Spontaneous parametric down-conversion ,W state ,Biexciton ,Quantum teleportation - Abstract
Entangled photons are efficiently generated from highly symmetric, site-controlled InGaAs/GaAs quantum dots grown in inverted pyramids. Fine-structure splitting of the intermediate exciton level is suppressed without the application of electric, magnetic or strain fields. Polarization entanglement is demonstrated by measurements of the two-photon density matrix and the confirmation of several entanglement criteria.
129. High-reflectance GaInP/GaAs distributed Bragg reflector
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J.D. Ganiere, B. Saint-Cricq, Alok Rudra, and Marc Ilegems
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Diffraction ,Materials science ,business.industry ,SURFACE-EMITTING LASERS ,DISTRIBUTED BRAGG REFLECTOR LASERS ,Epitaxy ,Distributed Bragg reflector ,Chemical beam epitaxy ,Gallium arsenide ,SEMICONDUCTOR LASERS ,chemistry.chemical_compound ,Wavelength ,Optics ,chemistry ,Distributed Bragg reflector laser ,Optoelectronics ,Wafer ,Electrical and Electronic Engineering ,business - Abstract
A high-reflectance GaInP/GaAs distributed Bragg reflector (DBR) was grown by chemical beam epitaxy (CBE). The mirror consists of 40 pairs of alternating layers and was designed for a centre wavelength of 980 nm, resulting in a total thickness of 5.8 mum. Highly stable growth conditions led to a maximum reflectance of 0.99 and to a variation in the centre wavelength of only 5 nm over the 2'' (50.8 mm) wafer. Transmission electron microscopy and X-ray diffraction measurements confirmed the vertical uniformity and the crystallographic quality of the sample.
130. Direct Evidence for Quantum Contact Resistance Effects in V-Groove Quantum Wires
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Alok Rudra, Benjamin Dwir, Eli Kapon, Alexander Palevski, Ivo Utke, and D. Kaufman
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Physics ,Condensed matter physics ,Web of science ,Direct evidence ,Quantum mechanics ,Quantum wire ,Quantum point contact ,Contact resistance ,Condensed Matter Physics ,Groove (engineering) ,Quantum ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials - Abstract
Reference LPN-ARTICLE-2000-013doi:10.1016/S1386-9477(00)00052-7View record in Web of Science Record created on 2008-02-29, modified on 2017-05-12
131. Site-Controlled Quantum-Wire and Quantum-Dot Photonic-Crystal Microcavity Lasers
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Pascal Gallo, M. Calic, Eli Kapon, Alessandro Surrente, Benjamin Dwir, K.A. Atlasov, Karl Fredrik Karlsson, Alok Rudra, and Marco Felici
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Materials science ,business.industry ,Quantum wire ,Physics::Optics ,Laser ,Optical microcavity ,law.invention ,Quantum dot ,Quantum dot laser ,law ,Optoelectronics ,Physics::Accelerator Physics ,business ,Lasing threshold ,Quantum ,Photonic crystal - Abstract
Based on site- and energy-controlled quantum wires (QWR) and quantum dots (QD), diverse photonic-crystal microcavity laser systems are proposed and discussed. Results demonstrating QWR lasing, cavity coupling and QD ordered arrays are presented.
132. Experimental method for high-accuracy reflectivity-spectrum measurements
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Alok Rudra, Eli Kapon, Arthur Schönberg, C.-A. Berseth, Klaus Leifer, and Oliver Dehaese
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Materials science ,Optical fiber ,business.industry ,Materials Science (miscellaneous) ,Physics::Optics ,Distributed Bragg reflector ,Laser ,Industrial and Manufacturing Engineering ,law.invention ,Quality (physics) ,Optics ,law ,Attenuation coefficient ,Reflection (physics) ,Optoelectronics ,Business and International Management ,Reflection coefficient ,business ,Beam (structure) - Abstract
An experimental method for accurate measurements of the reflectivity spectrum of mirrors is presented. It combines the noise reduction obtained with multiple beam reflections on two identical mirrors; high-beam quality, owing to the use of single-mode optical fibers; and high immunity against intensity variations of the beam. This method is demonstrated for characterizing a 30-period GaAs/Al(0.65)Ga(0.35)As distributed Bragg reflector designed for long-wavelength vertical-cavity surface-emitting lasers. Its peak reflectivity is found to be 99.43 ? 0.04% at 1.562 mum, and an optical absorption coefficient of alpha = 36 ? 6 cm(-1) is derived. The peak internal reflectivity of this distributed Bragg reflector used as the top mirror in a wafer-fused vertical-cavity surface-emitting laser is calculated to be 98.87 ? 0.12%, and the transmission is 0.28%.
133. Coupled Photonic-Crystal Cavities and Quantum-Wire Microlasers
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Alok Rudra, Eli Kapon, K.A. Atlasov, Karl Fredrik Karlsson, Pascal Gallo, Benjamin Dwir, and M. Calic
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Physics ,Quantum optics ,Photon ,business.industry ,Quantum wire ,Lasers ,Physics::Optics ,optical coupling ,Optics ,Quantum dot ,photonic crystals ,microcavity lasers ,semiconductor nanostructures ,Optoelectronics ,Spontaneous emission ,business ,Lasing threshold ,Quantum well ,Photonic crystal - Abstract
Strong optical confinement implemented with 2D photonic-crystal (PhC) microcavities provides a powerful tool for controlling the features of light-matter interaction. Combined with nanostructures such as quantum wells, quantum wires (QWRs) or quantum dots, the PhC cavities — efficiently controlling spontaneous emission [1] — are envisaged to bring superior semiconductor-laser performance [2], which could be exploited for applications in low-power-consumption integrated optoelectronics. Furthermore, inter-cavity optical coupling may allow for optimizing the laser output power [3] and realizing ultra-fast switching devices [4]. Here, we present experimental and numerical studies of directly coupled L 3 -type PhC microcavities that employ monolithically embedded site-controlled QWRs acting as local internal light sources. Using microphotoluminescence (PL) experiments [5], it is shown that such PhC system supports coupled modes with distinct resonant wavelengths and delocalized optical fields. It is also demonstrated that the cavity losses of these modes may “split” as well, in general. Furthermore, we demonstrate single-mode QWR-PhC microlasers. Low thresholds (∼1 µW) and relatively high spontaneous-emission coupling factors (β ∼ 0.3) are achieved. Lasing is established based on power-dependent linewidth narrowing [6] and time-resolved photon dynamics [7]. This work provides grounds for the development of more complex PhC systems for experiments in quantum physics [8] and microlasers [4].
134. Coulomb correlations of charged excitons in semiconductor quantum dots
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Alok Rudra, Emanuele Pelucchi, B. Chalupar, M. Byszewski, D. Y. Oberli, and Eli Kapon
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Physics ,Photoluminescence ,Zeeman effect ,Condensed Matter::Other ,Exciton ,Electron ,Fine Structure Splitting ,Condensed Matter Physics ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,Electronic, Optical and Magnetic Materials ,symbols.namesake ,Condensed Matter::Materials Science ,Spin ,Quantum dot ,Semiconductor nanostructures ,symbols ,Fine structure ,Wave vector ,Excitons ,Emission spectrum ,Atomic physics - Abstract
In this study, we present a systematic investigation of the emission spectra of excitonic complexes confined in QDs when an external magnetic field is applied in a direction perpendicular to the optical wave vector Voigt configuration. The effective g factors of an electron and a hole in individual QDs are obtained on the basis of a consistent analysis of the Zeeman splittings in many QDs. Our results reveal a large uniformity of the electron g factors but a broad variation in hole g factors when analyzing QDs emitting at nearly the same energy. By comparing the polarized emission spectra from the neutral and charged excitons in the same QD, we evidence a significant modification of the carrier g factors that we attribute to Coulomb correlations within the few-particle excitonic complexes. We use pyramidal In0.1Ga0.9As/Al0.3Ga0.7As QDs that allow us to observe simultaneously the positively and the negatively charged excitons in the same photoluminescence
135. Carrier-induced effects on absorption and emission in V-groove quantum wire diodes
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Helge Weman, Eli Kapon, Alok Rudra, E. Martinet, and M.-A. Dupertuis
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Physics ,Photoluminescence ,Condensed matter physics ,Quantum wire ,Electroluminescence ,Condensed Matter Physics ,Molecular physics ,Spectral line ,Electronic, Optical and Magnetic Materials ,Absorption edge ,SPECTRA ,Absorption (electromagnetic radiation) ,Spectroscopy ,Diode - Abstract
We report on carrier-induced effects on emission and absorption in forward biased GaAs/AlGaAs V-groove quantum wire (QWR) diodes observed using low-temperature (10 K) photoluminescence (PL), electroluminescence (EL) and PL excitation (PLE) spectroscopy. In the case of simultaneous electron-hole injection we observe a band-gap renormalization (BGR) of at least 5 meV for a carrier density of approximate to 10(6) cm(-1), by comparing high-density EL spectra with low-density PLE spectra. In the case of electron injection of approximate to 10(6) cm(-1) we observe a complete quenching of the PLE absorption edge related to a Burstein-Moss shift of approximate to 35 meV. Hole band-filling is much less effective due to smaller subband spacing and larger density-of-states in the valence band.
136. Site-Controlled InGaAs Quantum Dots with Tunable Emission Energy
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Pascal Gallo, Alok Rudra, Eli Kapon, Benjamin Dwir, Arun Mohan, and Marco Felici
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Photoluminescence ,Materials science ,Luminescence ,Surface Properties ,Nanophotonics ,photonics ,Physics::Optics ,Gallium ,quantum dots ,Substrate (electronics) ,Chemical vapor deposition ,semiconductors ,Growth ,Indium ,Arsenicals ,Arsenic ,Biomaterials ,Condensed Matter::Materials Science ,pattern formation ,Mechanisms ,General Materials Science ,Pyramid (geometry) ,Vapor-Phase Epitaxy ,business.industry ,crystal growth ,General Chemistry ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,Nanostructures ,Semiconductor ,Quantum dot ,Optoelectronics ,Photonics ,business ,Biotechnology - Abstract
Semiconductor quantum-dot (QD) systems offering perfect site control and tunable emission energy are essential for numerous nanophotonic device applications involving spatial and spectral matching of dots with optical cavities. Herein, the properties of ordered InGaAs/GaAs QDs grown by organometallic chemical vapor deposition on substrates patterned with pyramidal recesses are reported. The seeded growth of a single QD inside each pyramid results in near-perfect (
137. A terahertz quantum cascade. laser grown by low-pressure metalorganic vapor phase epitaxy
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Jérôme Faist, Maria I. Amanti, Alok Rudra, L. Sirigu, Eli Kapon, and Giacomo Scalari
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Distributed feedback laser ,Materials science ,Physics and Astronomy (miscellaneous) ,business.industry ,Far-infrared laser ,Physics::Optics ,Epitaxy ,Semiconductor laser theory ,Photomixing ,Condensed Matter::Materials Science ,Quantum dot laser ,Optoelectronics ,business ,Lasing threshold ,Plasmon - Abstract
Demonstration of a terahertz quantum cascade laser grown by a low-pressure metalorganic vapor phase epitaxy is reported. The structural analysis of the grown structure shows a very high degree of vertical uniformity and sharp interfaces. Lasing emission at λ=90μm up to 93K with a threshold current density Jth=330A∕cm2 at 7K was obtained in a structure incorporating a single plasmon waveguide.
138. Evaluation of InP/InGaAsP distributed Bragg reflectors grown by chemical-beam epitaxy
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J Behrend, Alok Rudra, Laurent Sagalowicz, Klaus Leifer, Eli Kapon, C.-A. Berseth, Jean-François Carlin, and O. Dehaese
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electron microscopy ,Chemistry ,business.industry ,Electron energy loss spectroscopy ,INP ,Atmospheric temperature range ,Condensed Matter Physics ,Distributed Bragg reflector ,Epitaxy ,Chemical beam epitaxy ,law.invention ,Inorganic Chemistry ,Optics ,law ,Transmission electron microscopy ,InGaAsP ,distributed Bragg reflector ,Materials Chemistry ,Electron microscope ,business ,Bar (unit) - Abstract
We have evaluated the structure of high-reflectivity InP/InGaAsP distributed Bragg reflectors grown by chemical-beam epitaxy at a growth rate of 3 mu m/h. Transmission electron microscopy combined with electron energy loss spectroscopy indicate lateral fluctuations in the GaInAsP alloy composition, clearly visible in the 490-510 degrees C growth temperature range, but less perceptible between 460 and 480 degrees C. In the higher temperature range, the modulation in composition shows a higher frequency along the [1 (1) over bar 0] direction than along [1 1 0].
139. Tilted-potential photonic crystal cavities for integrated quantum photonics
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Alessio Miranda, A. Lyasota, B. Rigal, Elyahou Kapon, Alok Rudra, Benjamin Dwir, and A. Delgoffe
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Physics ,Photon ,business.industry ,single photons ,Physics::Optics ,Purcell effect ,Atomic and Molecular Physics, and Optics ,localization ,Optics ,Quantum dot ,Wavelength-division multiplexing ,Photonics ,business ,Refractive index ,Quantum ,Photonic crystal - Abstract
We propose and investigate a new type of photonic crystal (PhC) cavity for integrated quantum photonics, which provides tailored optical modes with both confined and extended spatial components. The structures consist of elongated PhC cavities in which the effective index of refraction is varied quasi-linearly along their axis, implemented by systematic lateral shifts of the PhC holes. The confined modes have approximately Airy-function envelopes, exhibiting single peaks and extended tails, which is useful for optimizing single photon extraction and transmission in integrated quantum photonic devices. The measured spectrally resolved near-field patterns of such devices show the expected spatial and resonance wavelength behavior, in agreement with numerical simulations of the Airy-Bloch modes. The effects of fabrication-induced disorder on the mode features are also analyzed and discussed. Selective excitation of specific Airy-Bloch modes using integrated, site-controlled quantum dots as localized light sources is demonstrated. Based on the tilted-potential cavity, multiple-QD single photon emitters exploiting wavelength division multiplexing are proposed. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
140. Excited excitonic states observed in semiconductor quantum dots using polarization resolved optical spectroscopy
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V. Troncale, Anton V. Malko, Eli Kapon, Emanuele Pelucchi, M. Byszewski, D. Y. Oberli, Karl Fredrik Karlsson, and Alok Rudra
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Physics ,Photoluminescence ,Luminescence ,Linear polarization ,Exciton ,General Physics and Astronomy ,Polarization (waves) ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,Wires ,Condensed Matter::Materials Science ,Quantum dot ,Excited state ,Anisotropy ,Spontaneous emission ,Atomic physics ,Biexciton - Abstract
We present results on the polarization-resolved photoluminescence emitted from InGaAs/AlGaAs single quantum dots (QDs) grown in inverted tetrahedral pyramids. The emitted light was detected for two mutually perpendicular linear polarization directions in the less conventional cleaved-edge geometry, in addition to the standard top-emission geometry. Whereas the in-plane linear polarization was isotropic, as a consequence of the high symmetry of the system, we found a strong polarization anisotropy of the edge-emitted light revealing QD states of predominantly heavy- or light-hole character. By temperature control of the charge state, several neutral and charged light-hole like exciton complexes were identified. In particular, a biexciton showing a twofold radiative recombination path, leading to two nearly perpendicularly polarized emission multiplets, was identified. These results are also of technological relevance for any design of optoelectronic QD-integrated devices.
141. Growth of Gainas(P) and Gainasp/Gainas Mqw Structures by Cbe
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Jl Staehli, P. Ruterana, M. Gailhanou, Marc Ilegems, Alok Rudra, and J.-F. Carlin
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Diffraction ,Materials science ,Photoluminescence ,business.industry ,Physics::Optics ,Condensed Matter Physics ,Laser ,Line width ,law.invention ,Inorganic Chemistry ,Transmission electron microscopy ,law ,Lattice (order) ,Materials Chemistry ,Optoelectronics ,Angstrom ,business ,Quantum well - Abstract
We discuss the growth of lattice matched GaInAs, GaInAsP and GaInAsP/GaInAs multiple quantum well structures for high speed laser applications. Optical cavities, including five 90 angstrom GaInAs quantum wells with GaInAsP barriers and waveguides showed a 4 K photoluminescence line width of 8.7 meV. Transmission electron microscopy and X-ray diffraction confirm the good control over the growth of these structures.
142. Remote excitation between quantum emitters mediated by an optical Fano resonance
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Eli Kapon, Alessio Miranda, Yi Yu, B. Dwir, Alok Rudra, A. Lyasota, and A. Delgoffe
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Physics ,dots ,Fano resonance ,Physics::Accelerator Physics ,Physics::Optics ,Atomic physics ,entanglement ,Quantum ,Atomic and Molecular Physics, and Optics ,Excitation ,Electronic, Optical and Magnetic Materials - Abstract
Remote coupling between quantum emitters is of great importance for constructing quantum networks. Conventionally, this can be achieved via photon exchange by incorporating the quantum emitters in a waveguide or a large cavity. However, such photonic structures suffer from low quality-factors or large mode volumes, limiting the efficiency of light–matter interaction. Here, we demonstrate remote coupling between two site-controlled semiconductor quantum dot emitters mediated by an optical Fano resonance induced by coupling cavity modes via a continuum waveguide state. Unlike ordinary coupled modes, the Fano mode offers both a spatially extended field and a high local density of optical states at the emitters, enhancing light–matter interaction. This coupling scheme allows the demonstration of mutual excitation between two quantum dots separated in space by > 17 wavelengths. Our approach holds promise for achieving long-distance interaction without compromising interaction efficiency, which is essential for scaling up on-chip integration of quantum networks based on solid-state quantum emitters.
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