Abstract

The successful construction of a digital optical processor or photonic switching network depends on our ability to efficiently power and interconnect together arrays of optical logic devices. Thus components capable of generating, re-routing and fanning-out arrays of beams must be available if full advantage is to be taken of the parallelism and improved communications inherent in optics. This has led to a great deal of effort being invested into the design and fabrication of optical interconnects using, for example, bulk optics, computer generated holograms and volume phase holographic optical elements. At present, one of the most promising techniques is based on CGH‘s which have a continuous phase profile. Such holographic gratings, commonly referred to as kinoforms, can theoretically reconstruct arrays of equal intensity light beams with a diffraction efficiency approaching 100%. These CGH's are therefore ideal for many applications, ie array generation and fan-out, both of which are vital for the construction of a digital optical processor or a photonic switching network. The fabrication of optical elements which have continuous surface-relief or refractive index profiles is, unfortunately, an extremely demanding task. Much of the recent work in the field of array generation has therefore been devoted to the design of kinoforms which have only a few, discrete, equally spaced phase levels. Recently however we have demonstrated an alternative technique of fabricating kinoforms which is based on the concept of the hybrid hologram¹. This is a volume phase hologram recorded optically using a plane reference beam and an object wavefront generated from a binary amplitude CGH. By spatially filtering out all but the first diffraction order of the CGH it is possible to generate a uniform amplitude, continuous phase wavefront at the hologram plane, a form of wavefront ideal for recording a volume phase hologram.

© 1990 Optical Society of America