Square wave excitability in quantum dot lasers under optical injection

Neuromorphic dynamics with optically injected quantum dot lasers

“…This manifests as a deterministic square wave cycle between the remnants of the two states. Close to this deterministic cycle, the system is excitable and noise induced pulsations are obtained as shown in [40]. Such optothermal coupling has also previously been described in [27,29,[43][44][45][46][47].…”

“…The pump laser was operated at 40 mA, 1.25 times threshold. FIG.1 shows the evolution of the intensity with detuning (as previously shown in [40] but displayed again here for completeness).We begin with large negative detuning, where the frequency of the master is far less than that of the slave. Here a simple limit cycle was obtained.…”

“…A 300 µm long InAs based QD laser similar to the one used in [40] was optically injected with a tunable laser source (TLS) in a unidirectional master-slave configuration. The TLS had a linewidth of approximately 100 kHz.…”

“…It typically manifests in fast-slow systems and the Van der Pol Fitzhugh Nagumo model is the prototypical model used to describe it. Recently, such excitability has been reported for optically injected QD devices: When a QD laser is optically injected with high injection strength, excitable square pulses are obtained [40]. The duration of each square is constant and on the order of a microsecond but the rise and fall times of each square are on the order of a nanosecond.…”

“…Depending on the system specifics, one typically obtains either Type I excitability or Type II excitability [39], but not both. Recently however, we have demonstrated that optically injected QD lasers can display both Type I and Type II excitability [40]. We investigate the emergence of the Type II phenomenon in greater depth in this work.…”