All-Optical Toggle Flip-Flop Based on Monolithic Semiconductor Ring Laser

A novel monolithic all-optical flip-flop of the toggle type with two complementary outputs is demonstrated based on a semiconductor ring laser (SRL), where the intrinsic directional bistability of the SRL device is combined with the saturable absorption effect that takes place in the reverse-biased input waveguides. Toggle flip-flop (TFF) operation is experimentally demonstrated using optical trigger toggle pulses of 500 ps duration. The achieved bit-rate of 500 Mb/s is the highest reported so far for all-optical TFFs. The operational speed is limited by the carrier recovery time of the saturable absorbers; however, the proposed technology has potential for multi-gigabits per second operation.