Abstract: An optical computer includes a plurality of functional elements (thin-film elements) each adapted for causing an external signal to act on a two-dimensional-information incident light so as to perform information processing, and light sources for transferring the two-dimensional-information incident light between the functional elements. Each of the functional elements includes nanoparticles comprising molecules of an organic compound and associates/aggregates of these molecules. This structure makes it possible to input light beams from a plurality of functional elements to a single functional element and to output light beams from this single functional element to the plurality of functional elements.