Influence of Exciton-Exciton Interaction on Quantum Beats

Aoki, Takao; Mohs, G.; Kuwata‐Gonokami, Makoto; Yamaguchi, Atsushi

doi:10.1103/physrevlett.82.3108

Cited by 61 publications

(57 citation statements)

References 29 publications

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“…In addition, we have also performed PP differential transmission spectroscopy on a thin GaN sample, though not simultaneously with FWM. Our results show that the quantum beats as revealed in previous studies [2,3,4] …”

Section: Introductionsupporting

confidence: 86%

Exceptionally slow rise in differential reflectivity spectra of excitons in GaN: Effect of excitation-induced dephasing

et al. 2003

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Femtosecond pump-probe (PP) differential reflectivity spectroscopy (DRS) and four-wave mixing (FWM) experiments were performed simultaneously to study the initial temporal dynamics of the exciton line-shapes in GaN epilayers. Beats between the A-B excitons were found only for positive time delay in both PP and FWM experiments. The rise time at negative time delay for the differential reflection spectra was much slower than the FWM signal or PP differential transmission spectroscopy (DTS) at the exciton resonance. A numerical solution of a six band semiconductor Bloch equation model including nonlinearities at the Hartree-Fock level shows that this slow rise in the DRS results from excitation induced dephasing (EID), that is, the strong density dependence of the dephasing time which changes with the laser excitation energy.

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Section: Introductionsupporting

confidence: 86%

Exceptionally slow rise in differential reflectivity spectra of excitons in GaN: Effect of excitation-induced dephasing

et al. 2003

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“…To avoid polarisation pinning which is likely to be inevitable in quantum well cavities due to their reduced symmetry, the cavity is composed of bulk GaN. In this semiconductor, the different types of excitons are mixed and the excitonexciton interaction is expected to be spin isotropic [17] so that polariton BEC in such cavities should be accompanied by the spontaneous appearance of completely arbitrary polarisation. This device structure demonstrates strong exciton-photon coupling and polariton lasing at room temperature as we showed recently [5].…”

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confidence: 99%

Spontaneous Polarization Buildup in a Room-Temperature Polariton Laser

et al. 2008

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We observe the build up of strong (∼50%) spontaneous vector polarisation in emission from a GaN-based polariton laser excited by short optical pulses at room temperature. The Stokes vector of emitted light changes its orientation randomly from one excitation pulse to another, so that the timeintegrated polarisation remains zero. This behaviour is completely different to any previous laser. We interpret this observation in terms of the spontaneous symmetry breaking in a Bose-Einstein condensate of exciton-polaritons.PACS numbers: 71.36.+c, 03.75.Kk, Polariton lasers are coherent light sources based on emission of light from a coherent ensemble of excitonpolaritons -the mixed light-exciton quasiparticles in semiconductor microcavities. The concept of polariton lasing was first proposed in 1996 [1], followed a few years later by reports of coherent polariton emission in microcavities [2,3,4]. Recently, we reported polariton lasing at room temperature in GaN-based microcavities [5]. Apart from being very promising for applications, the concept of polariton lasing involves several fundamental physics issues. Contrary to conventional lasers, polariton lasers emit coherent and monochromatic light spontaneously. This is achieved when mixed light-matter quasiparticles (exciton-polaritons), Bosecondense inside a semiconductor microcavity. BoseEinstein condensation (BEC) of the polaritons is a subject of intense experimental and theoretical research at present. Several experimental works claiming polariton BEC have appeared recently [6,7,8]. Though polariton BEC implies polariton lasing these two phenomena are not identical. For polariton lasing a macroscopically populated quantum state of exciton polaritons must be created, which can be considered as a polariton condensate. Polariton lasing does not require thermal equilibrium in the system or the spontaneous build-up of the order parameter, which are the main criteria for BEC when understood as a thermodynamic phase transition. Which experimental measurement should be considered as decisive proof for the exciton-polariton BEC is still a subject of debate within the community. Thermalisation of the exciton-polaritons detected by angle-resolved photoluminescence (PL) measurements has been considered one of the key criteria for a long time [6,7]. However, a similar angular dependence of the PL has also been observed in GaAs-based photon lasers [9]. The spatial coherence of polariton emission demonstrated in Ref.[6] is characteristic for conventional lasers as well. Recent theoretical work suggests that observation of the spontaneous buildup of the vector polarisation in emission from polariton lasers would be evidence for the spontaneous symmetry breaking in the system [10,11,12]. In turn, spontaneous symmetry breaking is considered to be a smoking gun for BEC ever since the pioneering work of Goldstone [13,14].Here we report observations of the build up of the spontaneous vector polarization at room temperature in bulk GaN microcavities. Unlike the recent low temperature e...

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“…2(d) shows a small phase shift relative to = +4. In general, the QB phase is sensitive to the spin-dependent exciton-exciton interactions [33]. For a typical example, in bulk GaN, the QBs in the colinear polarization excitation show no phase shift while the QBs in the cocircular polarization excitation show a shift between X A and X B .…”

Section: A Exciton Oam Excited With Single-mode Lg Pulsesmentioning

confidence: 99%

Coherent dynamics of exciton orbital angular momentum transferred by optical vortex pulses

et al. 2016

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The coherent dynamics of the exciton center-of-mass motion in bulk GaN are studied using degenerate four-wave-mixing (FWM) spectroscopy with Laguerre-Gaussian (LG) mode pulses. We evaluate the exciton orbital angular momentum (OAM) dynamics from the degree of OAM, which is derived from the distributions of OAM (topological charge) of the FWM signals. When excitons are excited with two single-mode LG pulses, the exciton OAM decay time significantly exceeds the exciton dephasing time, which can be attributed to high uniformity of the exciton dephasing in our bulk sample because the decoherence of the exciton OAM is governed by the angular variation in the exciton dephasing. We also analyze the topological charge ( ) dependence of the OAM decay using a multiple-mode LG pump pulse, which allows us to simultaneously observe the dynamics of the exciton OAM for different values under the same excitation conditions. The OAM decay times of the = 1 component are usually longer than those of the = 0 component. The -dependent OAM decay is supported by a phenomenological model which takes into account the local nonuniformity of the exciton dephasing.

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Influence of Exciton-Exciton Interaction on Quantum Beats

Cited by 61 publications

References 29 publications

Exceptionally slow rise in differential reflectivity spectra of excitons in GaN: Effect of excitation-induced dephasing

Exceptionally slow rise in differential reflectivity spectra of excitons in GaN: Effect of excitation-induced dephasing

Spontaneous Polarization Buildup in a Room-Temperature Polariton Laser

Coherent dynamics of exciton orbital angular momentum transferred by optical vortex pulses

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