An all-optical flip-flop memory is built-up based on two ring lasers, where a semiconductor optical amplifier (SOA) is shared in two laser cavities. The flip-flop outputs short pulses that have tunable central wavelengths, a pulsewidth of 1.5 ps (FWHM) at 10 GHz, generated by actively modelocking using phase modulation. Bistability of the flip-flop is observed by introducing optical feedback via an external cavity. The static contrast ratio of the device is over 20 dB between the dominating and suppressed states and the switching power is as low as 18 dBm.
Yang, X., & Dorren, H. J. S. (2010). All-optical flip-flop memory using SOA-based modelocked ring lasers with optical feedback. Electronics Letters, 46(14), 1016-1017. https://doi.org/10.1049/el.2010.1136