Progress in diffractive phase gratings used for spot array generation

Abstract

Prototype free-space photonic switching[1] and optical computing systems[2] rely on spot array generating systems to produce illumination needed to transfer information between arrays of optical processing elements. In these systems, the light from a single laser is split into a set of beams that are focussed onto an array of optical logic devices, such as S-SEEDs[3]. Although several methods are available for generating spot arrays[4], diffraction gratings (also referred to as Dammann gratings[5] [6]) were chosen to generate the spot arrays. Their advantages can be traced to the ease with which they are incorporated into an optical system. As illustrated in figure 1, the grating is simply inserted into the collimated beam with the appropriate imaging optics. Their operation is relatively insensitive to alignment. Provided the collimated beam illuminates a suitable size area of the grating, the performance is determined by the design and fabrication process.