Luis Vina | Universidad Autónoma de Madrid (original) (raw)
Papers by Luis Vina
arXiv: Mesoscale and Nanoscale Physics, 2013
We study the dynamics of polariton condensate wave trains that propagate along a quasi one-dimens... more We study the dynamics of polariton condensate wave trains that propagate along a quasi one-dimensional waveguide. Through the application of tuneable potential barriers the propagation can be reflected and multiple reflections used to confine and store a propagating state. Energy-relaxation processes allow the delayed relaxation into a long-living coherent ground state. Aside the potential routing of polariton condensate signals, the system forms an AND-type logic gate compatible with incoherent inputs.
Journal of Applied Physics, 1986
We have grown high-purity GaAs on (100), (311)A, and (311)B orientations by molecular-beam epitax... more We have grown high-purity GaAs on (100), (311)A, and (311)B orientations by molecular-beam epitaxy (MBE). While undoped GaAs grown on (100) and (311)A are typically p type, growth on (311)B orientation has yielded n type with a liquid-nitrogen electron mobility of 1.3×105 cm2 V−1 s−1, which is among the highest mobilities reported for MBE-grown materials. Low-temperature photoluminescence showed well-resolved impurity
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](Le Journal de Physique Colloques, 1987
Surface Science, 1990
... The area of the points is proportional to the oscillator strenghts. L. Viha et al.i'Magn... more ... The area of the points is proportional to the oscillator strenghts. L. Viha et al.i'Magnetic fieldeffects in highly resolved 2D excitons 507 i ..JsyJ aao ^(2s) ^ . . ... [ 14] DC Rogers, J. Singleton, RJ Nicholas, CT Foxon and K. Woodbridge, Phys. Rev. B 34 ( 1986 ) 4002. ...
Superlattices and Microstructures, 1987
Solid State Communications, 2001
Semiconductor Science and Technology, 2000
Acta Physica Polonica A, 2004
Physical Review Letters, 2009
Physical Review Letters, 2007
Applied Physics Letters, 2007
Semiconductor Science and Technology, 2010
We report on novel exciton-polariton routing devices created to study and purposely guide light-m... more We report on novel exciton-polariton routing devices created to study and purposely guide light-matter particles in their condensate phase. In a co-directional coupling device, two waveguides are connected by a partially etched section which facilitates tunable coupling of the adjacent channels. This evanescent coupling of the two macroscopic wavefunctions in each waveguide reveals itself in real space oscillations of the condensate. This Josephson-like oscillation has only been observed in coupled polariton traps so far. Here, we report on a similar coupling behavior in a controllable, propagative waveguide-based design. By designing the gap width and channel length, the exit port of the polariton flow can be chosen. This co-directional polariton device is a passive and scalable coupler element that can serve in compact, next generation logic architectures.
We present a time-resolved photoluminescence (PL) study in real- and momentum-space of a polarito... more We present a time-resolved photoluminescence (PL) study in real- and momentum-space of a polariton condensate switch in a quasi-1D semiconductor microcavity. The polariton flow across the ridge is gated by excitons inducing a barrier potential due to repulsive interactions. A study of the device operation dependence on the power of the pulsed gate beam obtains a satisfactory compromise for the ON/OFF-signal ratio and -switching time of the order of 0.3 and 50 ps, respectively. The opposite transition is governed by the long-lived gate excitons, consequently the OFF/ON-switching time is 200 ps, limiting the overall operation speed of the device to 3 GHz. The experimental results are compared to numerical simulations based on a generalized Gross-Pitaevskii equation, taking into account incoherent pumping, decay and energy relaxation within the condensate.
We review some of the newest findings on the spin dynamics of carriers and excitons in GaAs/GaAlA... more We review some of the newest findings on the spin dynamics of carriers and excitons in GaAs/GaAlAs quantum wells. In intrinsic wells, where the optical properties are dominated by excitonic effects, we show that exciton-exciton interaction produces a breaking of the spin degeneracy in two-dimensional semiconductors. In doped wells, the two spin components of an optically created two-dimensional electron gas are well described by Fermi-Dirac distributions with a common temperature but different chemical potentials. The rate of the spin depolarization of the electron gas is found to be independent of the mean electron kinetic energy but accelerated by thermal spreading of the carriers.
We show that the use of momentum-space optical interferometry, which avoids any spatial overlap b... more We show that the use of momentum-space optical interferometry, which avoids any spatial overlap between two parts of a macroscopic quantum state, presents a unique way to study coherence phenomena in polariton condensates. In this way, we address the longstanding question in quantum mechanics: "Do two components of a condensate, which have never seen each other, possess a definitive phase?" [P. W. Anderson, Basic Notions of Condensed Matter Physics (Benjamin, 1984)]. A positive answer to this question is experimentally obtained here for light-matter condensates, created under precise symmetry conditions, in semiconductor microcavities taking advantage of the direct relation between the angle of emission and the in-plane momentum of polaritons.
arXiv: Mesoscale and Nanoscale Physics, 2013
We study the dynamics of polariton condensate wave trains that propagate along a quasi one-dimens... more We study the dynamics of polariton condensate wave trains that propagate along a quasi one-dimensional waveguide. Through the application of tuneable potential barriers the propagation can be reflected and multiple reflections used to confine and store a propagating state. Energy-relaxation processes allow the delayed relaxation into a long-living coherent ground state. Aside the potential routing of polariton condensate signals, the system forms an AND-type logic gate compatible with incoherent inputs.
Journal of Applied Physics, 1986
We have grown high-purity GaAs on (100), (311)A, and (311)B orientations by molecular-beam epitax... more We have grown high-purity GaAs on (100), (311)A, and (311)B orientations by molecular-beam epitaxy (MBE). While undoped GaAs grown on (100) and (311)A are typically p type, growth on (311)B orientation has yielded n type with a liquid-nitrogen electron mobility of 1.3×105 cm2 V−1 s−1, which is among the highest mobilities reported for MBE-grown materials. Low-temperature photoluminescence showed well-resolved impurity
Le Journal de Physique Colloques, 1987
Surface Science, 1990
... The area of the points is proportional to the oscillator strenghts. L. Viha et al.i'Magn... more ... The area of the points is proportional to the oscillator strenghts. L. Viha et al.i'Magnetic fieldeffects in highly resolved 2D excitons 507 i ..JsyJ aao ^(2s) ^ . . ... [ 14] DC Rogers, J. Singleton, RJ Nicholas, CT Foxon and K. Woodbridge, Phys. Rev. B 34 ( 1986 ) 4002. ...
Superlattices and Microstructures, 1987
Solid State Communications, 2001
Semiconductor Science and Technology, 2000
Acta Physica Polonica A, 2004
Physical Review Letters, 2009
Physical Review Letters, 2007
Applied Physics Letters, 2007
Semiconductor Science and Technology, 2010
We report on novel exciton-polariton routing devices created to study and purposely guide light-m... more We report on novel exciton-polariton routing devices created to study and purposely guide light-matter particles in their condensate phase. In a co-directional coupling device, two waveguides are connected by a partially etched section which facilitates tunable coupling of the adjacent channels. This evanescent coupling of the two macroscopic wavefunctions in each waveguide reveals itself in real space oscillations of the condensate. This Josephson-like oscillation has only been observed in coupled polariton traps so far. Here, we report on a similar coupling behavior in a controllable, propagative waveguide-based design. By designing the gap width and channel length, the exit port of the polariton flow can be chosen. This co-directional polariton device is a passive and scalable coupler element that can serve in compact, next generation logic architectures.
We present a time-resolved photoluminescence (PL) study in real- and momentum-space of a polarito... more We present a time-resolved photoluminescence (PL) study in real- and momentum-space of a polariton condensate switch in a quasi-1D semiconductor microcavity. The polariton flow across the ridge is gated by excitons inducing a barrier potential due to repulsive interactions. A study of the device operation dependence on the power of the pulsed gate beam obtains a satisfactory compromise for the ON/OFF-signal ratio and -switching time of the order of 0.3 and 50 ps, respectively. The opposite transition is governed by the long-lived gate excitons, consequently the OFF/ON-switching time is 200 ps, limiting the overall operation speed of the device to 3 GHz. The experimental results are compared to numerical simulations based on a generalized Gross-Pitaevskii equation, taking into account incoherent pumping, decay and energy relaxation within the condensate.
We review some of the newest findings on the spin dynamics of carriers and excitons in GaAs/GaAlA... more We review some of the newest findings on the spin dynamics of carriers and excitons in GaAs/GaAlAs quantum wells. In intrinsic wells, where the optical properties are dominated by excitonic effects, we show that exciton-exciton interaction produces a breaking of the spin degeneracy in two-dimensional semiconductors. In doped wells, the two spin components of an optically created two-dimensional electron gas are well described by Fermi-Dirac distributions with a common temperature but different chemical potentials. The rate of the spin depolarization of the electron gas is found to be independent of the mean electron kinetic energy but accelerated by thermal spreading of the carriers.
We show that the use of momentum-space optical interferometry, which avoids any spatial overlap b... more We show that the use of momentum-space optical interferometry, which avoids any spatial overlap between two parts of a macroscopic quantum state, presents a unique way to study coherence phenomena in polariton condensates. In this way, we address the longstanding question in quantum mechanics: "Do two components of a condensate, which have never seen each other, possess a definitive phase?" [P. W. Anderson, Basic Notions of Condensed Matter Physics (Benjamin, 1984)]. A positive answer to this question is experimentally obtained here for light-matter condensates, created under precise symmetry conditions, in semiconductor microcavities taking advantage of the direct relation between the angle of emission and the in-plane momentum of polaritons.