Abstract

Previously we presented optical implementations of neural networks that use parallel optical interconnections between neurons.¹ In these systems, the nonlinear neural response is carried out electronically after detecting the optical signal. However, this would be better implemented by means of custom, parallel-optical in–optical/out–electro-optic spatial light modulators (SLM's). Here we present two types of such SLM's fabricated from amorphous silicon (a- Si:H)/FLC and VLSI/FLC technologies. In both cases, the input beam carrying the information from the previous layer of neurons is detected and is transformed into an electric current. This current is then electronically processed, and the resultant voltage is applied across an FLC modulator, which spatially modulates the output optical beam. For the a-Si:H/FLC device, simple linear subtractions between spatially separated optical channels can be achieved, with a nonlinear response obtained through the switching characteristic of the FLC.² This is particularly applicable in optical implementations that use bipolar interconnection weights.¹

© 1990 Optical Society of America