Theory of microscopic semiconductor lasers with external optical feedback.

The properties of microscopic semiconductor lasers with external optical feedback are theoretically analysed. The size-dependence of the critical feedback level, at which the laser first becomes unstable, is clarified, showing how the dominant indicator of feedback stability is the gain of the laser, irrespective of size. The impact of increased spontaneous emission β-factors and over-damped operation is evaluated, exposing a diminished phase sensitivity of microscopic lasers, and a trade-off between modulation bandwidth and feedback stability is identified.

Theory of slow-light semiconductor optical amplifiers.

We have developed an efficient framework for analyzing the reflection and transmission properties of semiconductor photonic crystal optical amplifiers. Specifically, we have investigated the use of slow light to enhance the gain of short integrated amplifiers. We find that the expected enhancement in transmission is limited by distributed feedback induced by the material gain itself.

All-optical non-linear activation function for neuromorphic photonic computing using semiconductor Fano lasers.

We predict that semiconductor Fano lasers can be used to realize an all-optical non-linear activation function for neuromorphic photonic computing. By exploiting optical control of a Fano mirror, the laser can generate optical pulses with low threshold energy, gigahertz repetition rates, and orders of magnitude suppression between the on- and off-states. Analytical estimates of the switching threshold energy, extinction ratio, and refractory period agree well with numerical results.

Suppression of Coherence Collapse in Semiconductor Fano Lasers.

We show that semiconductor Fano lasers strongly suppress dynamic instabilities induced by external optical feedback. A comparison with conventional Fabry-Perot lasers shows orders of magnitude improvement in feedback stability and in many cases even total suppression of coherence collapse, which is of major importance for applications in integrated photonics. The laser dynamics are analyzed using a generalization of the Lang-Kobayashi model for semiconductor lasers with external feedback, and an analytical expression for the critical feedback level is derived.

Modes, stability, and small-signal response of photonic crystal Fano lasers.

Photonic crystal Fano lasers have recently been realised experimentally, showing useful properties such as pinned single-mode lasing and passive pulse generation. Here the fundamental properties of the modes of the Fano laser are analysed, showing how the laser functionality depends sensitively on the system configuration. Furthermore the laser stability is investigated and linked to the small-signal response, which shows additional dynamics that cannot be explained with a conventional rate equation model, including a damping of relaxation oscillations and a frequency modulation bandwidth that is only limited by the nanocavity response.