Optically Controlled Jitter Generator
  A new simple circuit producing random pulse trains is proposed and experimentally studied. The circuit is composed of an operational amplifier and two feedback links, one of which comprises two photodiodes. The photodiodes are responsible for nonlinearity in the feedback. By varying the illumination it is possible to control the nonlinearity in the photodiode current-voltage characteristics and change the degree of randomness in the oscillations. The circuit's simplicity and optical control make it attractive for coupled map lattices. 
Julia Manasson and V. A. Manasson