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Spontaneous spatial patterns occur in nonlinear optical systems where spatial coupling is present through diffraction and/or diffusion. Patterns usually consist of repeated units, and such units may exist in isolation as localized structures. Such structures are somewhat akin to spatial solitons, and are now usually known as cavity solitons They can exist in cavities hosting a variety of nonlinear media, in particular semiconductors. Because they can act as malleable, re-configurable optical pixels, they are potentially useful in image and/or information processing.
In order that cavity solitons can really be used in such applications, it is necessary that they can be created (and erased) at will, that configurations of them can be controlled to prevent errors, and that many of them can be manipulated and/or stored as complexes, i.e. structures composed of potentially-arbitrary combinations of solitons (1s) and soliton-vacancies (0s). In each of these topics, viz. Creation, control and complexes of cavity solitons, both experimental and theoretical progress are being made. Equally, however, significant open questions and major unsolved problems remain. In this talk these questions are discussed and illustrated, with examples taken from semiconductor and other experiments and from basic theoretical models and associated simulations. |
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