Adaptive image transmission with a pattern forming system

Summary form only given. Photorefractive materials are well-suited for pattern observation since their intrinsically slow dynamics offers the opportunity to perform real-time measurements and observations. A single-feedback configuration creating two counterpropagating beams in the nonlinear optical medium gives rise to transverse modulational instability above a certain threshold. This instability generally leads to the formation of hexagonal patterns. In the case of the photorefractive feedback system, patterns of non-hexagonal geometry can be excited by changing the distance between the crystal and the feedback mirror. In addition, the powerful tool of spatial filtering can be applied to manipulate the system in a way that e.g. non-hexagonal patterns become dominant in a parameter region where the hexagon is the natural output of the system. From the point of view of all-optical image processing, this phenomenon can be interpreted as a distribution of a laser beam into an adaptive number of spots with the same intensity. Thus, switches from one to six, four or two channels can be realized. Taking into account higher order terms, other possible configurations of distributing channels are accessible. Our aim is to investigate the prospects of transmitting an image into these self-organized channels. We present experimental results for image transmission of simple geometric figures into the spatial sidebands, proving the principle function of our adaptive image processing system.