Multistate optical memory based on serially interconnected lasers

A multistate optical memory based on serially interconnected lasers is presented. We show that only one of the lasers can lase at a time, thus, the state of the optical memory is determined by the wavelength of the dominant laser. The light from the dominant laser suppresses its neighboring lasers through gain saturation, but still receives amplification by the active element of the suppressed lasers, compensating for coupling losses. This light passes through each of the successive lasers, simultaneously suppressing and being amplified. By this mechanism, all other lasers are suppressed. A five-state optical memory based on this concept is experimentally demonstrated. The contrast ratio between different states is over 30 dB. Dynamic flip-flop operation based on two different all-optical switching methods is also demonstrated.