Formation Of Cavity Polaritons Research Articles

Long-Range Transport of Organic Exciton-Polaritons Revealed by Ultrafast Microscopy

We directly measure micron-scale transport in organic materials, induced by strong coupling and formation of cavity polaritons. Using ultrafast microscopy we follow the motion of polaritons in real-time, finding that their propagation is surprisingly slow.

Cavity polaritons in one-dimensional photonic crystals containing dye molecule–titanate nanosheet hybrids

We investigated the optical properties of one dimensional photonic crystal (1D-PC) microcavity with a wedge-shaped cavity layer containing fluorescent pseudoisocyanine (PIC)-gelatin and nonfluorescent PIC–H1.07Ti1.73O4∙nH2O (HTO) nanohybrids. In the case of the PIC-gelatin, the formation of cavity polaritons with a Rabi splitting energy of 49.2 meV was clearly observed. Contrary to our expectations, the formation of cavity polaritons in the case of the PIC–HTO nanohybrids was also observed, even though their splitting energy of 5.8 meV was small. Although different possible explanations were considered, at present, there is insufficient information to completely explain the phenomena. The formation of cavity polaritons with nonfluorescent excitons is indeed very rare and therefore interesting.

Room-Temperature Fluorescence Lifetime of Pseudoisocyanine (PIC) J Excitons with Various Aggregate Morphologies in Relation to Microcavity Polariton Formation

The results of room-temperature fluorescence lifetime measurements are reported for the excitation of J aggregates (Js) of pseudoisocyanine chloride (PIC-Cl) prepared in potassium polyvinyl sulfate (PVS) polymer thin films, their aqueous solutions, and NaCl aqueous solutions. Variations of the microscopic morphologies of the aggregates were investigated. The results show that fluorescence decay features correlated to the morphology change. The observed fluorescence lifetime and quantum efficiency of PIC J aggregates (PIC-Js) in a NaCl aqueous solution were 310 ps and 28%, respectively. The lifetime of the fibril-shaped macroaggregates prepared in PVS thin films was below the instrumental time resolution of 5 ps, and the efficiency decreased to below 3%. The results indicate that PIC-Js prepared with PVS polymers have an increased nonradiative contribution to the excitation deactivation process. In particular, macro-Js with isolated fibril-shaped structures revealed nonradiative pathway(s) that are closely associated to the specific packaging morphology of the constituent meso-Js. The possibility of a destructive effect on the formation of cavity-polaritons is also discussed.

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

Recent theoretical and experimental work on linear exciton-light coupling in single and coupled semiconductor microcavities is reviewed: emphasis is given to angular dispersion and polarization effects in the strong-coupling regime, where cavity-polariton states are formed. The theoretical formulation is based on semiclassical theory. The energy of single-cavity modes is determined by the Fabry-Perot frequency ω c as well as by the center of the stop band ω s of the dielectric mirrors; the phase delay in the dielectric mirrors carries a nontrivial angle-and polarization dependence. The polarization splitting of cavity modes depends on the mismatch between ω c and ω s, and increases with internal angle as sin2 θ eff. Interaction between the cavity mode and quantum-well (QW) excitons is described at each angle by a two-oscillator model, whose parameters are expressed in terms of microscopic quantities. Weak and strong coupling regimes and the formation of cavity polaritons are described. Comparison with experimental results on a GaAs-based cavity with In0.13Ga0.87As QWs shows that a quantitative understanding of polariton dispersion and polarization splitting has been achieved. Coupling of two identical cavities through a central dielectric mirror induces an optical splitting between symmetric and antisymmetric modes. When QW excitons are embedded in both cavities at antinode positions, the system behaves as four coupled oscillators, leading to a splitting of otherwise degenerate exciton states and to separate anticrossing of symmetric and antisymmetric modes. These features are confirmed by experimental results on coupled GaAs cavities with In0.06Ga0.94As QWs. An analysis of reflectivity lineshapes requires the inclusion of the effect of resonance 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 experimental findings.