Optical processor and neuromorphic processor

A linear algebraic processor is provided, for instance for performing vector matrix multiplications as part of a neural network. Light emitting diode strips 4 are formed on one substrate 1 and are illuminated in accordance with the values of elements of an input vector. Photodiode strips 8 are arranged orthogonally to the light emitting diode strips 4 on another substrate 2. A ferro-electric liquid crystal layer 3 is disposed between the strips 4 and 8 and provided with polarisers and electrodes 7 and 9 to permit the light attenuation properties of each matrix element between facing portions of the light emitting diode strips 4 and photodiode strips 8 to be varied and stored in a non-volatile way. The optical attenuation represents the value of the elements of the matrix and the outputs of the photodiode strips 8 represent the value of the elements of an output vector formed as the product of the input vector and the matrix. The optical attenuation of the ferro-electric liquid crystal can be incremented or decremented by applying suitable voltages to the electrodes so as to create electric fields across the liquid crystal matrix elements.