Strong light-matter coupling in ultrathin double dielectric mirror GaN microcavities

Strong light-matter coupling is demonstrated at low temperature in an ultrathin GaN microcavity fabricated using two silica/zirconia Bragg mirrors, in addition to a three-period epitaxial (Al,Ga)N mirror serving as an etch stop and assuring good quality of the overgrown GaN. The λ/2 cavity is grown by molecular beam epitaxy on a Si substrate. Analysis of angle-resolved data reveal key features of the strong coupling regime in both reflectivity and transmission spectra at 5 K: anticrossing with a normal mode splitting of 43±2 meV and 56±2 meV for reflectivity and transmission, respectively, and narrowing of the lower polariton linewidth near resonance

Fabrication and Optical Properties of a Fully Hybrid Epitaxial ZnO-Based Microcavity in the Strong Coupling Regime

In order to achieve polariton lasing at room temperature, a new fabrication methodology for planar microcavities is proposed: a ZnO-based microcavity in which the active region is epitaxially grown on an AlGaN/AlN/Si substrate and in which two dielectric mirrors are used. This approach allows as to simultaneously obtain a high-quality active layer together with a high photonic confinement as demonstrated through macro-, and micro-photoluminescence ({\mu}-PL) and reflectivity experiments. A quality factor of 675 and a maximum PL emission at k=0 are evidenced thanks to {\mu}-PL, revealing an efficient polaritonic relaxation even at low excitation power.Comment: 12 pages, 3 figure

Strong light-matter coupling in bulk GaN-microcavities with double dielectric mirrors fabricated by two different methods

Two routes for the fabrication of bulk GaN microcavities embedded between two dielectric mirrors are described, and the optical properties of the microcavities thus obtained are compared. In both cases, the GaN active layer is grown by molecular beam epitaxy on (111) Si, allowing use of selective etching to remove the substrate. In the first case, a three period Al0.2Ga0.8N / AlN Bragg mirror followed by a lambda/2 GaN cavity are grown directly on the Si. In the second case, a crack-free 2,mu m thick GaN layer is grown, and progressively thinned to a final thickness of lambda. Both devices work in the strong coupling regime at low temperature, as evidenced by angle-dependent reflectivity or transmission experiments. However, strong light-matter coupling in emission at room temperature is observed only for the second one. This is related to the poor optoelectronic quality of the active layer of the first device, due to its growth only 250 nm above the Si substrate and its related high defect density. The reflectivity spectra of the microcavities are well accounted for by using transfer matrix calculations. (C) 2010 American Institute of Physics. [doi:10.1063/1.3477450

LO-phonon assisted polariton lasing in a ZnO based microcavity

Polariton relaxation mechanisms are analysed experimentally and theoretically in a ZnO-based polariton laser. A minimum lasing threshold is obtained when the energy difference between the exciton reservoir and the bottom of the lower polariton branch is resonant with the LO phonon energy. Tuning off this resonance increases the threshold, and exciton-exciton scattering processes become involved in the polariton relaxation. These observations are qualitatively reproduced by simulations based on the numerical solution of the semi-classical Boltzmann equations

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

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

Influence of the mirrors on the strong coupling regime in planar GaN microcavities

The optical properties of bulk $\lambda/2$ GaN microcavities working in the strong light-matter coupling regime are investigated using angle-dependent reflectivity and photoluminescence at 5 K and 300 K. The structures have an Al$_{0.2}$Ga$_{0.8}$N/AlN distributed Bragg reflector as the bottom mirror and either an aluminium mirror or a dielectric Bragg mirror as the top one. First, the influence of the number of pairs of the bottom mirror on the Rabi splitting is studied. The increase of the mirror penetration depth is correlated with a reduction of the Rabi splitting. Second, the emission of the lower polariton branch is observed at low temperature in a microcavity containing two Bragg mirrors and exibiting a quality factor of 190. Our simulations using the transfer-matrix formalism, taking into account the real structure of the samples investigated are in good agreement with experimental results.Comment: published versio