Cavity-polariton dispersion and polarization splitting in single and coupled semiconductor microcavities

Recent theoretical and experimental work on linear exciton-light coupling i n single and coupled semiconductor microcavities is reviewed: emphasis is g iven to angular dispersion and polarization effects in the strong-coupling regime, where cavity-polariton states are formed. The theoretical formulati on is based on semiclassical theory. The energy of single-cavity modes is d etermined by the Fabry-Perot frequency omega(c) as well as by the center of the stop band omega(s) of the dielectric mirrors; the phase delay in the d ielectric mirrors carries a nontrivial angle- and polarization dependence. The polarization splitting of cavity modes depends on the mismatch between omega(c) and omega(s), and increases with internal angle as sin(2)theta(eff ). Interaction between the cavity mode and quantum-well (QW) excitons is de scribed at each angle by a two-oscillator model, whose parameters are expre ssed in terms of microscopic quantities. Weak and strong coupling regimes a nd the formation of cavity polaritons are described. Comparison with experi mental results on a GaAs-based cavity with In0.13Ga0.87As QWs shows that a quantitative understanding of polariton dispersion and polarization splitti ng has been achieved. Coupling of two identical cavities thorugh a central dielectric mirror induces an optical splitting between symmetric and antisy mmetric modes. When QW excitons are embedded in both cavities at antinode p ositions, the system behaves as four coupled oscillators, leading to a spli tting of otherwise degenerate exciton states and to separate anticrossing o f symmetric and antisymmetric modes. These features are confirmed by experi mental results on coupled GaAs cavities with In0.06Ga0.94As QWs. An analysi s of reflectivity lineshapes requires the inclusion of the effect of resona nce narrowing of cavity polaritons. Finally, the polarization splitting in a coupled cavity depends both on the single-cavity factors and on the angle - and polarization dependence of the optical coupling between the cavities. Inclusion of all these effects provides a good description of the experime ntal findings. (C) 1999 American Institute of Physics. [S1063-7834(99)00108 -2].