Whispering gallery modes in zinc oxide micro‐ and nanowires

Czekalla, C.; Nobis, Thomas; Rahm, A.; Cao, Bingqiang; Zúñiga‐Pérez, Jesús; Sturm, Chris; Schmidt‐Grund, Rüdiger; Lorenz, Michael; Grundmann, Marius

doi:10.1002/pssb.200945527

Cited by 83 publications

(68 citation statements)

References 56 publications

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“…Our observation is also consistent with Ref. [24], where only TE-polarized WGMs switch to the photonic lasing regime. Having a closer look at a momentum profile [see Fig.…”

Section: P Dietrich Et Alsupporting

confidence: 93%

Parametric relaxation in whispering gallery mode exciton-polariton condensates

et al. 2015

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Polariton condensation of one-dimensional multimode whispering gallery mode exciton polaritons is investigated in hexagonal ZnO microwires at cryogenic temperatures. At threshold, stimulated scattering is fed by the resonant emission from highly populated defect-bound excitons. With further increasing excitation power, condensates relax within the multimode whispering gallery mode polariton ladder, leading to their effective evaporative cooling. The relaxation is a parametric polariton-polariton scattering process evidenced by its intensity, energy, and momentum evolution. The experimental observations are in good agreement with numerical simulations based on a model for polariton-polariton scattering extended to the multimodal whispering gallery mode system. [4]. Multimode polariton systems that undergo inter-or intrabranch parametric scattering processes [5][6][7] are promising for sources of entangled photons [8][9][10]. However, using those effects in integrated optical circuits requires manipulability and guidability that is more easily achieved in one-dimensional microcavities. A major step towards this goal has recently been demonstrated in polariton microcavities etched into wire-shaped structures resulting in the formation of one-dimensional polariton condensates with long polariton lifetimes and long propagation lengths [11]. Although parametric oscillation processes have already been demonstrated in those structures [6], a richer mode structure is necessary for the creation of entangled polaritons [8]. Our "bottom up" approach for the creation of one-dimensional multimode polariton systems combines the excellent photonic properties of whispering gallery modes (WGMs) with the outstanding electronic properties of excitons in hexagonal ZnO microwires. Beneficially, ZnO microwires can easily be grown by carbothermal vapor-phase transport [12] and naturally provide strong photonic confinement by total internal reflection (TIR) [13]. Hence, they obviate the need for highly reflecting Bragg mirrors and sophisticated fabrication steps. One-dimensional WGM exciton-polariton condensates in those ZnO microwires then benefit from the multimodal character of the photonic component along with a long photon lifetime. * cpd3@st-andrews.ac.uk † schmidt-grund@physik.uni-leipzig. de Here, we demonstrate the condensation of WGM exciton polaritons at cryogenic temperature being accompanied by complex parametric polariton scattering processes. We observe an efficient exciton relaxation into defect-bound states, whose radiative decay resonantly excites the polariton condensate above threshold in one of the many lower polariton branches. By increasing the excitation power, condensate relaxation into further lower polariton states takes place, providing an efficient evaporative cooling mechanism. We show experimentally and theoretically that this process is caused by multichannel scattering mechanisms leading to parametric mixing of polariton states at higher excitation densities, as evidenced by constant energy and momen...

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“…Our observation is also consistent with Ref. [24], where only TE-polarized WGMs switch to the photonic lasing regime. Having a closer look at a momentum profile [see Fig.…”

Section: P Dietrich Et Alsupporting

confidence: 93%

Parametric relaxation in whispering gallery mode exciton-polariton condensates

et al. 2015

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“…The lasing threshold is found to be ≈ 0.28 MW cm − 2 , which is comparable to those obtained at low temperature. [ 12 ] In order to understand the lasing mechanism, a μ -PL spectrum under low excitation density is enlarged and plotted in where D is the diameter of the circle that circumscribes the polygon, m is the number of facets, and R is the refl ectivity of the facets. If the laser was quasi-WGM or WGM, it can be deduced that the refl ectivity is about 89.35% for a quasi-WGM cavity and 93.71% for a WGM cavity.…”

Section: Doi: 101002/adma201100423mentioning

confidence: 99%

Room Temperature Excitonic Whispering Gallery Mode Lasing from High‐Quality Hexagonal ZnO Microdisks

et al. 2011

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“…[12], the impact of deformation away from straight facets and sharp edges has been investigated for m ¼ 3 and m ¼ 4. WGM have been experimentally studied in triangular [15], square [16], hexagonal [17,18], and dodecagonal [19] cavities. In particular hexagonal cavities ( Fig.…”

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confidence: 99%

Whispering gallery modes in deformed hexagonal resonators

Grundmann

Dietrich

2012

Physica Status Solidi (b)

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Optical resonances in polygonal resonators are due to whispering gallery modes (WGM). We investigate WGM in regular and deformed hexagonal ZnO microwire resonators. Four types of geometries are investigated: regular hexagonal and dodecagonal cross sections, hexagonal cross section elongated for one pair of facets and hexagonal cross section deformed by bending (uniaxial stress). Experimental data on mode energies and angular dispersion are correlated with model calculations and Poincaré surfaces of section. Hexagonal (ϕ = 60°), square (ϕ = 45°), triangular (ϕ = 30°), and Fabry–Pérot modes (ϕ = 0°) are observed in the various investigated geometries, ϕ being the angle of incidence at the facets with respect to the normal direction. magnified image Hexagonal WGMs (green, 6‐WGM), triangular (red, 3‐WGM), and double‐triangular (blue, D3‐WGM) rays in regular hexagons, elongated hexagons and hexagons deformed by bending. Triangular WGMs are stable modes in all three resonators. Hexagonal modes are not stable in the bent hexagon.

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Whispering gallery modes in zinc oxide micro‐ and nanowires

Cited by 83 publications

References 56 publications

Parametric relaxation in whispering gallery mode exciton-polariton condensates

Parametric relaxation in whispering gallery mode exciton-polariton condensates

Room Temperature Excitonic Whispering Gallery Mode Lasing from High‐Quality Hexagonal ZnO Microdisks

Whispering gallery modes in deformed hexagonal resonators

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