Dynamics of Nonlinear Polariton Wavepackets and Pattern Formation in Microcavity Structures

Nonlinear wavepackets, such as solitons, are seen in many areas of physics. A promising medium where they could be used in both classical and quantum computational devices is the exciton-polariton system. Exciton-polaritons are quasi-particles consisting of strongly coupled excitons and photons. Polariton-polariton interactions result in a system with a high degree of nonlinearity. In this thesis, the dynamics of nonlinear wavepackets and pattern formation in several microcavity structures are studied. Initially, the formation of a polariton condensate in a periodic potential induced by a Surface Acoustic Wave (SAW) is investigated, with a particular focus on the role played by phonons absorbed as polaritons scatter between certain states. This process can result in the formation of "gap solitons". It is further suggested that reflections of the SAW from features on the sample can contribute to pattern formation in the emission spot. Later chapters focus on nonlinear wavepackets propagating with high momentum which could be used for the transmission of signals across a polaritonic chip. Patterns of bright dissipative polariton solitons are studied in planar microcavities. Arrays can be generated with solitons arranged either along or perpendicular to the propagation direction, with different localisation mechanisms employed in each case. Finally, the dynamics of soliton-like wavepackets propagating through quasi one dimensional microwire structures are investigated. Measurements of the quantum properties of these nonlinear wavepackets reveal non-classical behaviour. Multi-peak patterns are observed as the excitation power is increased, accompanied by discontinuities in phase between the peaks for higher power cases. At high excitation powers, broadening of the energy spectrum is observed in a similar manner to the supercontinuum generation which has previously been seen in optical fibres