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Cavity Solitons

Multidimensional spatio-temporal localisation phenomena and pattern formation in semiconductor microcavities

Photonic structures, and in particular semiconductor microcavities containing resonant media, provide a uniquely advantageous combination of nonlinear properties thereby allowing highly nonlinear modes of propagation. The semiconductor microcavity represents a photonic structure specifically designed to amplify coherent light-matter interactions. The cavity photons are confined between Bragg mirrors and interact resonantly with the fundamental transition of the quantum well located at the cavity centre. The interplay between Bragg reflections that block light propagation in photonic bandgaps, and the dynamical modifications of these reflections by coherent nonlinear light-matter interactions results in a unique type of nonlinear mode, localised both in space and time, which we call cavity SIT-soliton. In order to model the spatio-temporal dynamics in more complex multilayer planar geometries, such as semiconductor microcavities (Fig.8) the dynamical model has been extended to two spatial dimensions.

Fig.8. 2D refractive index profile of a GaInNAs semiconductor microcavity designed at λ=1.3 mm

We have numerically demonstrated the phenomenon of a two-dimensional SIT-soliton pattern formation and stationary population inversion gratings in resonantly absorbing semiconductor microresonators (Fig.9, 10).

                            (a)                                                         (b)                                                           (c)                     
Fig.9. Light field and population inversion in a microcavity when an intense ultrashort (t~100 fs) pulse is injected in z-direction. (a,b) electric field pattern in the y and z direction (c) formation of a spatially-immobile population inversion grating. The simulated structure is a 5l GaAs cavity filled with absorbing medium; bottom DBR: 31 pairs GaAs/AlAs; top DBR: 24 pairs Al0.5Ga0.5As/Al0.8Ga0.2As

The predicted phenomena have the potential to be exploited for optical storage of information and parallel optical signal processing utilising spatial solitons as fast mobile information carriers in a new type of information processing device.

Fig.10. Time evolution of the population inversion and formation of intracavity patterns for l=1.3 mm geometry and pulse width t=100 fs 
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