Coherence effects in light scattering of two-dimensional photonic disordered systems: Elastic scattering of cavity polaritons

Abstract

Resonant scattering by cavity polaritons in a semiconductor microcavity is investigated. The bidimensional photonic behavior is well shown by the angular spread of the Rayleigh scattered light on the elastic cone. Moreover, the strong coupling between the excitonic oscillator and the cavity mode enables the simultaneous observation of both ͑i͒ universal properties of disordered systems such as coherent backscattering over a large angular width, and ͑ii͒ scattering anisotropy due to the microscopic nature of the scatterer.Interference and coherence effects in elastic light scattering from disordered systems have been the focus of wide interest due to their importance in many domains of physics. 1 They have also been revived by the analogies that could be made with theories and experiments developed for the propagation of electrons in disordered systems, such as the weak and strong localization regimes. 2 For electron systems, such studies have been seen as direct evidence of the quantum nature of the electron and resulted in the breakdown of classical transport descriptions such as the diffusion equation or the Boltzmann equation.For photons, coherence effects also led to the reexamination of radiative transfer equations. 1 Of paramount importance was the observation for electrons or photons of weak localization in the form of coherent backscattering ͑CBS͒, which provides an unambiguous signature of phase coherence in the system. 1 The latter experiments are usually carried out in a large variety of physical systems ͑thin films, dielectric spheres, rods, etc.͒, where the disorder is due to fluctuations of the real part of the effective refraction index originating in either composition or size fluctuations of the scatterers. These systems allow one to adjust the scatterer density to yield a favorable ratio of light wavelength () to light mean free path (l*). 3 In other light scattering experiments the light frequency is resonant with an elementary electronic excitation. In such studies the disorder being observed is the one acting on the resonant electronic excitations. 4-8 The light reemitted by the system consists of ͑i͒ a coherent, elastic part due to static disorder, called resonant Rayleigh scattering ͑RRS͒; ͑ii͒ an incoherent, elastic part called resonant hot luminescence, involving inelastic scattering events such as phonon scattering; ͑iii͒ partially or completely thermalized contributions called photoluminescence ͑PL͒. These emissions yield information on the energy level scheme and nature of these levels, as well as on their dynamics. This is well demonstrated in twodimensional ͑2D͒ semiconductor quantum wells ͑QW's͒: early work on RRS demonstrated exciton localization effects and the existence of a mobility edge 9 while more recent studies dealt with the dynamics of RRS, 10,11 and the speckle spectroscopy of disorder. 12 In this paper, we report on resonant elastic light scattering in a 2D system where the light-matter interaction is in the strong-coupling regime. We use semiconductor microcavities, whe...

Interaction-shaped vortex-antivortex lattices in polariton fluids

“…In our experiment we use a high finesse GaAs microcavity (F = 3000) with a polariton lifetime τ = 15 ps and a Rabi splitting of 5.1 meV [40][41][42] (see Appendix A: Sample description). The microcavity is excited with a continuous-wave single-mode Ti:Sa laser quasi resonant with the lower polariton branch at 837 nm.…”

Spatial Coherence and Stability in a Disordered Organic Polariton Condensate

“…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].…”

Observation of the optical spin Hall effect

“…Thus, when an initial polariton state with a given in-plane wavevector, k = (k x , k y ), and a given polarization state, transverse magnetic or transverse electric, is created, it is efficiently scattered towards states with in-plane wavevectors different from the initial one and with the same polarization state. As the modulus of k is conserved, this scattering gives rise to the Rayleigh scattering ring in the far-field emission 26,27 . Then the anisotropy in the orientation of the effective magnetic field creates an anisotropy in the polarization: in two opposite quadrants of the elastic circle, σ + polarization appears, whereas in the two others, σ − polarization appears (see Fig.…”