  Spatial solitons can exist in various kinds of nonlinear optical resonators
with and without amplification. In the past years different types of these
localized structures such as vortices, bright, dark solitons and phase solitons
have been experimentally shown to exist. Many links appear to exist to fields
different from optics, such as fluids, phase transitions or particle physics.
These spatial resonator solitons are bistable and due to their mobility suggest
schemes of information processing not possible with the fixed bistable elements
forming the basic ingredient of traditional electronic processing. The recent
demonstration of existence and manipulation of spatial solitons in emiconductor
microresonators represents a step in the direction of such optical parallel
processing applications. We review pattern formation and solitons in a general
context, show some proof of principle soliton experiments on slow systems, and
describe in more detail the experiments on semiconductor resonator solitons
which are aimed at applications.
