Fixed holographic optical interconnects for neural networks

The non-interacting nature and free spsce propagation of light allows optical interconnectioni with higher degree of connectivity then is pouible with conventional electronic integrated circuits where the interacting electroni must travel along paths which do not meet and where the geometry is confined to two dimensions. Optical interconnection can be realised in free space with arrays of computer generated holograms (CGHs) and are suitable for the interconnection of neural networks. Fan-out presents a problem of low diffraction efficiency and quantisation noise due to the dynamic range of the associated Fourier transform used to encode the hologram. Manipulation of the phase of individual output spots diminLshes the dynamic range and helps to alieviate this problem. Systems assembled using commercially available SLMs, detector arrays and computer workstations together with the CGH arrays are described and the realisation of more complex systems discussed.