Materials for optical computing

Information superhighways exploit optical-pulse propagation in silica fibre. Will the computers at the ends of the highway likewise exploit the optical representation of information? In the 1960s the first schemes for all-optical digital computers were proposed. In the 1990s emphasis has shifted to optical interconnection of arrays of semiconductor smart pixels. This paper presents reasons for this shift and, by complete contrast, possible applications for natural materials such as bacteriorhodopsin.