Nonlinear Neurons Using the Fieldshielding Effect in Photorefractive CdTe

A key element in the optical implementation of any neural network is the nonlinear neuron. The most common required feature of this device is a saturating response to an activation input. The activation input is the weighted sum of all the incident beams which are routed through an interconnection network to the neuron. We report on nonlinear neurons using the fieldshielding effect in photorefractive crystals which perform an incoherent addition of the incident intensities1,2. The device responds to CW or synchronously pulsed inputs in a variety of saturated, thresholded or bidirectional manners. Using photorefractive CdTe:In, we demonstrate a response to both inhibitory and excitatory inputs with a high sensitivity to incident light in the 1.0-1.4 μm range.