IMAGE TRANSCRIPTION BETWEEN ARRAYS OF N-P-N-P OPTOELECTRONIC SWITCHES

Double-heterojunction optical thyristors with a low holding current (0.2 mu-A/6 x 10(-4) cm2) and a low breakover current (70 nA/6 x 10(-4) cm2) have been fabricated. Such thyristors can be made to switch when receiving an optical input signal from a twin device. Excellent uniformity and stability of the characteristics are obtained in arrays of such thyristors. Monolithic arrays of 25 thyristors connected in parallel have been processed. Winner-takes-all operation can be achieved in such arrays: when applying a bias to the array, only the one thyristor receiving maximum input light switches on, while all others are inhibited from reaching the on-state. With this system, the maximum of a light input pattern can be detected with a resolution of 0.3 nW-or 30 pJ for pulsed input light signals. Finally, we demonstrate image transcription between thyristor arrays: the on-state of more than one thyristor can be copied with a single electrical pulse to the corresponding thyristors of a twin array.