Impact of disorder on high quality factor III-V nitride microcavities

Christmann, Gabriel; Simeonov, D.; Butté, R.; Feltin, E.; Carlin, J.-F.; Grandjean, N.

doi:10.1063/1.2420788

Cited by 68 publications

(44 citation statements)

References 19 publications

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“…[18] Similar results are obtained across the wafer, with variation mainly due to the local quality factor of the Bragg mirrors. [19] The time-integrated polarisation of emission we observe is exactly zero, independent of the orientation of the analyser axes. To resolve the polarisation of the emission for each experimental realisation of the condensation from each excitation pulse, we polarisation split the emission and focus both orthogonal components either a) onto the input slit of a Streak Camera operated in single-shot mode, or b) onto the cathodes of balanced PMTs.…”

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confidence: 87%

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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confidence: 87%

Spontaneous Polarization Buildup in a Room-Temperature Polariton Laser

et al. 2008

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“…7,8,10,11 Instead, DBRs made of semiconductor materials epitaxially grown on a crystalline substrate should enable to maintain a high crystalline quality, but require in turn a much larger number of pairs to obtain Qs similar to those achievable with dielectric materials. 12 The nitrides family (AlInGaN) seems to be more promising for fabricating the DBR than the (ZnMgCdO) one, as it presents a larger refractive index contrast within the family while keeping the same crystalline phase (i.e. wurtzite vs rocksalt).…”

Section: Lpn-cnrs Route De Nozay 91460 Marcoussis Francementioning

confidence: 99%

“…1,2 However, nitride-based DBRs are not easy to fabricate and face a number of problems. These include: (i) a large built-in strain that accumulates during the DBR growth, due to differences in the lattice parameters of the DBR materials, especially when AlN/GaN or AlN/AlGaN with high Ga content are used; 13 (ii) the formation of cracks due to the thermal expansion coefficient mismatch between nitrides and certain substrates; 14 and (iii) the spatial inhomogeneity of the photonic properties, 12 arising because of thickness or composition fluctuations.…”

Section: Lpn-cnrs Route De Nozay 91460 Marcoussis Francementioning

confidence: 99%

Patterned silicon substrates: A common platform for room temperature GaN and ZnO polariton lasers

Zúñiga‐Pérez

Mallet

Hahe

et al. 2014

Applied Physics Letters

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A new platform for fabricating polariton lasers operating at room temperature is introduced: nitride-based distributed Bragg reflectors epitaxially grown on patterned silicon substrates. The patterning allows for an enhanced strain relaxation thereby enabling to stack a large number of crack-free AlN/AlGaN pairs and achieve cavity quality factors of several thousands with a large spatial homogeneity. GaN and ZnO active regions are epitaxially grown thereon and the cavities are completed with top dielectric Bragg reflectors. The two structures display strong-coupling and polariton lasing at room temperature and constitute an intermediate step in the way towards integrated polariton devices.

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“…First, GaN MCs exhibit a significant disorder. 25 One, thus, expects a significant part of the oscillator strength from the LPs and the upper polaritons (UPs) to be shared with the uncoupled "dark" exciton modes in MQW MCs. 26 In addition, excitons confined in GaN QWs efficiently bind into biexcitons.…”

Section: Introductionmentioning

confidence: 99%

Impact of biexcitons on the relaxation mechanisms of polaritons in III-nitride based multiple quantum well microcavities

et al. 2012

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We report on the direct observation of biexcitons in a III-nitride based multiple quantum well microcavity operating in the strong light-matter coupling regime by means of nonresonant continuous wave and time-resolved photoluminescence at low temperature. First, the biexciton dynamics is investigated for the bare active medium (multiple quantum wells alone) evidencing localization on potential fluctuations due to alloy disorder and thermalization between both localized and free excitonic and biexcitonic populations. Then, the role of biexcitons is considered for the full microcavity: in particular, we observe that for specific detunings the bottom of the lower polariton branch is directly fed by the radiative dissociation of either cavity biexcitons or excitons mediated by one LO-phonon. Accordingly, minimum polariton lasing thresholds are observed, when the bottom of the lower polariton branch corresponds in energy to the exciton or cavity biexciton first LO-phonon replica. This singular observation highlights the role of excitonic molecules in the polariton condensate formation process as being a more efficient relaxation channel when compared to the usually assumed acoustical phonon emission one.

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Impact of disorder on high quality factor III-V nitride microcavities

Cited by 68 publications

References 19 publications

Spontaneous Polarization Buildup in a Room-Temperature Polariton Laser

Spontaneous Polarization Buildup in a Room-Temperature Polariton Laser

Patterned silicon substrates: A common platform for room temperature GaN and ZnO polariton lasers

Impact of biexcitons on the relaxation mechanisms of polaritons in III-nitride based multiple quantum well microcavities

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