Showing papers by "Alexey Kavokin published in 2004"
TL;DR: It is shown by direct thermally detected optical absorption measurements that the true band gap of InN is markedly wider than the currently accepted 0.7 eV.
Abstract: The deviations on the band-gap of InN which were linked to the precipitation of indium in the metallic phase that leads to additional optical losses associated with Mie resonances were discussed. The two sets of InP epilayers were examined by both plasma-assisted molecular beam epitaxy (MBE) and metal-organic chemical vapor deposition (MOCVD) on sapphire. The Mie resonance for InN layers were important because of the activation in the In aggregation phenomena in the alloys. The results show that bright infrared emission arises in a close vicinity of In inclusions and was likely associated with surface states at the metal/InN interfaces.
197 citations
TL;DR: This work reports the first observation of oscillations of the electromagnetic field in an optical superlattice based on porous silicon, an optical equivalent of well-known electronic Bloch oscillations in crystals.
Abstract: We report the first observation of oscillations of the electromagnetic field in an optical superlattice based on porous silicon. These oscillations are an optical equivalent of well-known electronic Bloch oscillations in crystals. Elementary cells of our structure are composed by microcavities whose coupling gives rise to the extended collective modes forming optical minigaps and minibands. By varying thicknesses of the cavities along the structure axis, we have created an effective electric field for photons. A very high quality factor of the confined optical state of the Wannier-Stark ladder may allow lasing in porous silicon-based superlattices.
124 citations
TL;DR: It is shown that giant longitudinal-transverse splitting of the polaritons mixes their spin states, which results in beats between right- and left-circularly polarized photoluminescence of microcavities, as was recently experimentally observed.
Abstract: We present the quantum theory of momentum and spin relaxation of exciton-polaritons in microcavities. We show that giant longitudinal-transverse splitting of the polaritons mixes their spin states, which results in beats between right- and left-circularly polarized photoluminescence of microcavities, as was recently experimentally observed [M. D. Martin et al., Phys. Rev. Lett. 89, 077402 (2002)]. This effect is strongly sensitive to the bosonic stimulation of polariton scattering.
92 citations
TL;DR: In this article, the stimulated scattering of polaritons in a semiconductor microcavity in the strong coupling regime results in a dramatic build-up of the circular polarization degree of light emitted by the cavity.
Abstract: We demonstrate experimentally that stimulated scattering of exciton--polaritons in a semiconductor microcavity in the strong coupling regime results in a dramatic build-up of the circular polarization degree of light emitted by the cavity. Moreover, we show that the polarization of the emitted light can be different from the polarization of the pumping light, e.g., pumping with a linearly polarized beam we detect a circularly polarized emission. This proves that the stimulated scattering of polaritons selects and amplifies a given polarization and inhibits all spin-relaxation processes. We believe that strong coupling microcavities can be used as building blocks for spin-dependent optoelectronic devices aimed at manipulations with the polarization of light on a micro- to nano-scale.
68 citations
61 citations
TL;DR: The theory of spin relaxation of exciton polaritons treated as a gas of weakly interacting bosons has been studied in this article, which is based on the spin density matrix approach in the Born-Markov approximation.
Abstract: We present the theory of spin relaxation of exciton polaritons treated as a gas of weakly interacting bosons. The model is based on the spin density matrix approach in the Born-Markov approximation. In its framework we have described the spin and energy relaxation of exciton-polaritons in semiconductor microcavities accounting for polariton-polariton and polariton-acoustic phonon scattering. We include various mechanisms of spin relaxation linked with the fine structure of the polaritons. The kinetic equation for time-dependent intensity and polarization of light emitted by the microcavities both at resonant and nonresonant pumping is obtained. The parametric amplification regime, in which the resonant polariton-polariton scattering plays the major role, is specifically analyzed. We show that the polarization plane of the emitted light can rotate as a function of the polarization degree of the pumping light which is a manifestation of the ``spin-optronic'' effect of self-induced Larmor precession of polariton pseudospins.
55 citations
TL;DR: In this article, the coexistence of low threshold lasing and strong coupling in a high-quality semiconductor microcavity under near-resonant optical pumping is reported.
Abstract: We report the coexistence of low threshold lasing and strong coupling in a high-quality semiconductor microcavity under near-resonant optical pumping. A sharp laser mode splits from the lower-polariton branch and approaches the bare cavity mode frequency as the pump power increases. The lasing is produced by low density localized exciton states, which are weakly coupled to the cavity mode. The appearance of this lasing mode distinguishes quantum-well excitons into those which are strongly or weakly coupled with the cavity mode.
27 citations
TL;DR: In this paper, a toy model of two oscillators reaching equilibrium through coupling to a thermal bath was studied to gain insights into the mechanism responsible for coherence buildup in an assembly of conserved bosons.
Abstract: We study a toy model of two oscillators reaching equilibrium through coupling to a thermal bath to gain insights into the mechanism responsible for coherence buildup in an assembly of conserved bosons. We show how, in some conditions, coherence can appear spontaneously out of thermal states, i.e., without prior existence in the system. We then study the dynamics when particles have a finite lifetime and the overall mean number is maintained by pumping. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
25 citations
TL;DR: In this article, the second-order coherence of light emitted by polariton lasers has been studied, and it was shown that the coherence introduced into the polariton condensate by an external source can be conserved by the system over a macroscopically long time.
Abstract: We study theoretically the second-order coherence g(2)(0) of light emitted by polariton lasers, i.e., devices based on stimulated relaxation and condensation of exciton–polaritons in microcavities. We solve kinetic equations for the polaritons in different approximations and show that (i) the coherence introduced into the polariton condensate by an external source can be conserved by the system over a macroscopically long time, and (ii) if the total number of polaritons is fixed by the excitation conditions, the correlations between the populations of the ground and excited polariton states can also result in the spontaneous buildup of second-order coherence in the polariton condensate. Both results are obtained neglecting polariton–polariton interactions in the condensate.
12 citations
10 citations
TL;DR: In this paper, it is argued that this behaviour can be explained if there is stimulated emission from photonic states in the photonic bandgap, which are strongly localized due to disorder.
Abstract: Synthetic opals filled with CdTe exhibit a pronounced decrease of the intensity of photoluminescence for photon energies within the photonic band-gap. However, the intensity of emission increases much faster with the level of pumping inside the photonic band-gap than outside. It is argued that this behaviour can be explained if there is stimulated emission from photonic states in the photonic bandgap, which are strongly localized due to disorder. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
TL;DR: In this paper, a new transistor based on stimulated scattering of electron-hole pairs into the BCS polariton mode was proposed, and the phase diagram for the system was calculated.
Abstract: Bose-condensation of mass-less quasiparticles (photons) can be easily achieved at the room temperature in lasers. On the other hand, condensation of bosons having a non-zero mass requires usually ultra-low temperatures. Recently, it has been shown that polaritons, which are half-light-half-matter quasi-particles, may form condensed states at high temperatures (up to 300K). Polaritons composed by electron-hole pairs coupled to confined light modes in optical cavities may form a Bardeen-Cooper-Schriefer (BCS) superfluid. We propose a new transistor based on stimulated scattering of electron-hole pairs into the BCS polariton mode. A pn-junction embedded inside an optical cavity resonantly emits light into the cavity mode. If the cavity mode energy slightly exceeds the band-gap energy, it couples with electron-hole pairs with zero centre of mass wave-vector but non-zero wave-vector of relative motion. This creates a super-current in the plane of the structure. In an isotropic case, its direction is chosen by the system spontaneously. Otherwise, it is pinned to the external in-plane bias. We calculate the phase diagram for the electron-hole-polariton system.
TL;DR: In this paper, a formalism based on non-local dielectric response theory and Green function techniques has been developed to describe the interaction of quantum well excitons with an evanescent optical wave of a planar waveguide.
Abstract: A formalism based on non-local dielectric response theory and Green function techniques has been developed to describe the interaction of quantum well excitons with an evanescent optical wave of a planar waveguide. Reflection spectra of a system in which a quantum well placed behind a dielectric interface at which light experiences total internal reflection have been calculated. It is shown that the spectral feature corresponding to the exciton resonance becomes much more pronounced if the angle of incidence is close to the critical angle of total internal reflection. The concept of a generalized Snell law has been applied to provide simplification of the formalism.
TL;DR: The authors withdraw their articles published in phys. sol. (a) 192, 212 (2002) and phys. stat. (b) 195, 563 (2003) as discussed by the authors.
Abstract: The authors withdraw their articles published in phys. stat. sol. (a) 192, 212 (2002) and phys. stat. sol. (a) 195, 563 (2003). (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
TL;DR: In this paper, the authors observed experimentally pronounced beats of the intensity of photoluminescence from a bottleneck region of a microcavity in the strong coupling regime and showed theoretically that the process of polariton-polariton scattering leading to the mixing between bright and dark polariton states is responsible for this effect.
Abstract: We observe experimentally pronounced beats of the intensity of photoluminescence from a bottleneck region of a microcavity in the strong coupling regime. These beats are extremely sensitive to the pumping intensity and vanish for the weak pumping. We show theoretically that the process of polariton-polariton scattering leading to the mixing between bright and dark polariton states is responsible for this effect. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)