Abstract
We review results on the optical injection of dual state InAs quantum dot-based semiconductor lasers. The two states in question are the so-called ground state and first excited state of the laser. This ability to lase from two different energy states is unique amongst semiconductor lasers and in combination with the high, intrinsic relaxation oscillation damping of the material and the novel, inherent cascade like carrier relaxation process, endows optically injected dual state quantum dot lasers with many unique dynamical properties. Particular attention is paid to fast state switching, antiphase excitability, novel information processing techniques and optothermally induced neuronal phenomena. We compare and contrast some of the physical properties of the system with other optically injected two state devices such as vertical cavity surface emitting lasers and ring lasers. Finally, we offer an outlook on the use of quantum dot material in photonic integrated circuits.
Highlights
Quantum confinement of carriers in semiconductor material is responsible for many of the technological advances in modern technology, being central to the vast majority of semiconductor lasers in use worldwide
For very short devices or where losses are high, GS emission can be entirely removed, and excited states (ESs) emission only obtained[32]. This dual state nature opens up the possibility for many unique optical injection scenarios, of interest for fundamental science and for technological applications; chief among these are bistabilities with switching mechanisms and neuromorphic functionality. We focus on these below and look forward to exciting integration developments and photonic integrated circuits based on Quantum dot (QD) lasers[33]
For optically injected single mode QD lasers operated in the GS only regime, the injected light can cause the intensity of the emitted light to exceed that of the free-running emission but for certain combinations of the injection strength and the detuning, it can cause it to drop below the free-running value as shown experimentally in[87] and numerically in[83]
Summary
The experimental hysteresis results described above are reproduced successfully for control parameters where the free-running behaviour of the QD laser is emission from the ES only. For optically injected single mode QD lasers operated in the GS only regime, the injected light can cause the intensity of the emitted light to exceed that of the free-running emission but for certain combinations of the injection strength and the detuning, it can cause it to drop below the free-running value as shown experimentally in[87] (see Fig. 5.24 therein) and numerically in[83]. A short pulse momentarily increasing the injection strength can induce a switch back to the ES off Boundary dynamics In conventional optical injection configurations, dynamics are typically found and studied near locking/ unlocking boundaries and the dynamical regimes obtained depend on the bifurcations leading to phase locking. This intrinsic Q switching phenomenon is unique to QD lasers, arising directly from the carrier cascade pathway described above without any requirement for multisection fabrication
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