Generation of random on-off modulation pulses by optically injecting a gain-switched Fabry-Pérot semiconductor laser...

We study the generation of random on-off modulation pulses by optically injecting a gain-switched Fabry-Pérot semiconductor laser with a dual-mode injection for random-modulation pulsed lidar applications. In the dual-mode injection scheme proposed, the first master laser (ML1) injecting on a resonant sidemode of the gain-switched slave laser (SL) randomly locks such injected sidemode and suppresses the output pulses in the center mode through gain-competition. The second master laser (ML2) injecting on the center mode then stabilizes and enhances the output pulses to have equal amplitudes suitable for digital threshold detection and time-correlated single photon counting. Under different injection conditions, we identify dynamical states including unlocked, stable locking, bistable, and instability. By operating the laser in the bistable states randomly switching between the unlocked and stable locking states, we successfully generate random on-off modulation pulses without employing any digital circuits or external modulators. We analyze the signal-to-noise ratio (SNR) and detection probability of the proposed scheme to show its feasibility in random-modulation pulsed lidar applications. Moreover, we study its anti-interference capability by adding interference from additional channels with similar modulated pulses. We show that, with injection strengths of 0.418 and 0.038 from the ML1 and ML2 and a correlation length T_c = 90 µs, a detection probability of 1 can be readily achieved even under the interference from more than 49 additional channels.