  Using a rate-equation model we numerically evaluate the carrier concentration
and photon number in an integrated two-section semiconductor laser, and analyse
its dynamics in three-dimensional phase space. The simulation comprises compact
model descriptions extracted from a commercially-available generic InP
technology platform, allowing us to model an applied reverse-bias voltage to
the saturable absorber. We use the model to study the influence of the injected
gain current, reverse-bias voltage, and cavity mirror reflectivity on the
excitable operation state, which is the operation mode desired for the laser to
act as an all-optical integrated neuron. We show in phase-space that our model
is capable of demonstrating four different operation modes, i.e. cw,
self-pulsating and an on-set and excitable mode under optical pulse injection.
In addition, we show that lowering the reflectivity of one of the cavity
mirrors greatly enhances the control parameter space for excitable operation,
enabling more relaxed operation parameter control and lower power consumption
of an integrated two-section laser neuron.
