Bit-Error-Rate measurement for an All-optical Set-Reset Flip-Flop based on semiconductor ring laser

In this work, the authors report on the demonstration of a monolithic semiconductor ring laser (SRL) as an all-optical set-reset flip-flop (SRFF). The SRL has a racetrack cavity, with 150 mum radius connecting two straight sections of 200 mum. Two straight output waveguides provide 4 input/output ports that can be used to inject/extract optical signals. The devices operate continuous wave at room temperature, with threshold currents between 35 and 60 mA, emitting up to 3 mW at lambda= 1550-1570 nm. The SRL exhibits inherent directional bistability: lasing action can occur unidirectionally either in the clockwise (CW) or in the counter-clockwise (CCW) direction. The lasing direction of the bistable SRL can be switched by an external optical signal that is injected into the SRL in the direction to be activated, with a response time around 100 ps.