Experimental study of disorder in a semiconductor microcavity

Gurioli, Massimo; Bogani, F.; Wiersma, D.S.; Roussignol, Philippe; Cassabois, Guillaume; Khitrova, G.; Gibbs, H. M.

doi:10.1103/physrevb.64.165309

Cited by 36 publications

(35 citation statements)

References 14 publications

(20 reference statements)

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“…Organics offer the advantage of a broad spectral range beyond that covered by GaN and ZnO and can be easily fabricated without the need for epitaxial growth. As-grown films, however, tend to be highly disordered and to overcome possible localization effects [12][13][14][15][16][17][18][19][20][21][22][23][24], the first demonstration of organic polariton condensation used a single-crystalline organic semiconductor as the active material [1]. Two recent demonstrations, however, have shown that the same phenomenology can be extended to amorphous systems: one consisting of a spin-coated polymer [3] and the other of a thermally evaporated oligomer [2].…”

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Spatial Coherence and Stability in a Disordered Organic Polariton Condensate

2015

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Although only a handful of organic materials have shown polariton condensation, their study is rapidly becoming more accessible. The spontaneous appearance of long-range spatial coherence is often recognized as a defining feature of such condensates. In this work, we study the emergence of spatial coherence in an organic microcavity and demonstrate a number of unique features stemming from the peculiarities of this material set. Despite its disordered nature, we find that correlations extend over the entire spot size and we measure g(1) (r, r ) values of nearly unity at short distances and of 50% for points separated by nearly 10 µm. We show that for large spots, strong shot to shot fluctuations emerge as varying phase gradients and defects, including the spontaneous formation of vortices. These are consistent with the presence of modulation instabilities. Furthermore, we find that measurements with flat-top spots are significantly influenced by disorder and can, in some cases, lead to the formation of mutually incoherent localized condensates.PACS numbers: 67.85. Hj, 81.05.Fb, 42.55.Sa, 71.36.+c In the last few years, a number of molecular systems that show room-temperature polariton condensation have emerged [1][2][3]. Polaritons are hybrid excitonphoton quasiparticles that form in optical microcavities when dissipation is low as compared to the the lightmatter interaction. Like their fundamental constituents, they obey Bose statistics at low densities. They inherit an effective mass as low as 10 −10 times that of a Rb 87 atom from their photonic component. Meanwhile, they collide with other polaritons and excitons due to an effective interaction stemming from their matter component. In inorganic microcavities, these features have been exploited to demonstrate rich phenomenology associated with Bose-Einstein condensation (BEC). The most wellknown of these effects is the macroscopic occupation of the ground state beyond a critical density n c . A perhaps more important consequence of the phase transition is the sudden appearance of off-diagonal long range order (ODLRO) in coordinate space [4,5]. This manifests itself in the non-vanishing long-range behaviour of the first-order spatial coherence g (1) (r, r'). At the polariton condensation threshold, a similar transition occurs, thus breaking U(1) symmetry, but also showing a number of distinct features resulting from the strongly non-equilibrium nature of the system [6].Several materials have been used to demonstrate polariton condensation. The majority of these have used CdTe-and GaAs-based semiconductors whose operation is limited to low temperatures due to their small exciton binding energy. Recently, however, wide bandgap semiconductors such as ZnO and GaN have emerged as viable materials for room-temperature applications [7][8][9][10]. Organic semiconductors are especially attractive in this context due to their large exciton binding energy. Molecular excitons are commonly of the Frenkel type where both electron and hole are localized on a single molecu...

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Spatial Coherence and Stability in a Disordered Organic Polariton Condensate

2015

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“…In GaAs/AlAs microcavities such crosshatches influence the propagation of polaritons and give rise to elastic scattering and the appearance of a cross-shaped signature in the far-field emission from a microcavity. [2][3][4][5][6] Furthermore, they can cause a localization of polariton condensates observed in such microcavities in the strong coupling regime. 7 In order to observe polariton fluid propagation over distances exceeding hundreds of lm, and spontaneous vortex dynamics in a homogeneous polariton superfluid, the cross-hatch pattern needs to be suppressed.…”

Section: Suppression Of Cross-hatched Polariton Disorder In Gaas/alasmentioning

confidence: 99%

Suppression of cross-hatched polariton disorder in GaAs/AlAs microcavities by strain compensation

2012

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“…In nominally planar samples it is typically observed that the cavity mode is elastically scattered on a crosshatched dislocation pattern [12][13][14][15][16] , while the excitonic part tends to exhibit a more isotropic disorder on the relevant micrometer length scale. In samples grown by MOCVD, additional random disorder is observed, indicating a fluctuation of the layer thickness in the micrometer spatial range due to the growth mode influenced by transport of the reactants via the gas-phase, allowing for nonhomogeneous deposition.…”

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Polariton states bound to defects in GaAs/AlAs planar microcavities

et al. 2012

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We report on polariton states bound to defects in planar GaAs/AlAs microcavities grown by molecular beam epitaxy. The defect types relevant for the spatial polariton dynamics in these structures are cross-hatch misfit dislocations, and point-like defects extended over several micrometers. We attribute the latter defects to Ga droplets emitted occasionally by the Ga cell during the growth. These defects, also known as oval defects, result in a dome-like local modulation of surface, which is translated into the cavity structure and leads to a lateral modulation of the cavity polariton energy of up to 15 meV. The resulting spatially localized potential landscape for the in-plane polariton motion creates a series of bound states. These states were characterized by spectrally resolved transmission imaging in real and reciprocal space, and reveal the spatial potential created by the defects. Interestingly, the defect states exhibit long lifetimes in the 10 ps range, which we attribute to a spatially smooth confinement potential.

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Experimental study of disorder in a semiconductor microcavity

Cited by 36 publications

References 14 publications

Spatial Coherence and Stability in a Disordered Organic Polariton Condensate

Spatial Coherence and Stability in a Disordered Organic Polariton Condensate

Suppression of cross-hatched polariton disorder in GaAs/AlAs microcavities by strain compensation

Polariton states bound to defects in GaAs/AlAs planar microcavities

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