Scalability and miniaturization of optoelectronic hopfield networks based around micro- and diffractive optical elements

It is generally accepted that diffractive optical elements provide the optimal flexibility for the implementation of free-space interconnections between arrays of optoelectronic components. In this paper we discuss the Hopfield neural network demonstrator based around a 2D array of Vertical-Cavity Surface-Emitting Lasers and an off-the-shelf Si photodetector array. The interconnection matrix between the optoelectronic arrays is provided by a diffractive optical element, the precise nature of which is determined by the problem to be solved by the network. In order to study the potential of the optoelectronic Hopfield network topology for both scalability and miniaturization, the design and micro-fabrication techniques used in the creation of diffractive optical elements will be analyzed. This analysis will allow estimates to be made of the maximum number of devices that may be interconnected using diffractive optical elements as well as outlining possible approaches to system miniaturization by the use of micro-optical elements.