Optically induced hysteresis in a two-state quantum dot laser

Abstract

Quantum dot lasers can lase from the ground state only, simultaneously from both the ground and first excited states and from the excited state only. We examine the influence of optical injection at frequencies close to the ground state when the free-running operation of the device is excited state lasing only. We demonstrate the existence of an injection-induced bistability between ground state dominated emission and excited state dominated emission and the consequent hysteresis loop in the lasing output. Experimental and numerical investigations are in excellent agreement. Inhomogeneous broadening is found to be the underlying physical mechanism driving the phenomenon.

Stability of Optically Injected Two‐State Quantum‐Dot Lasers

“…Figure b and c now show that the same kind of bistability also occurs in the two‐state (between and ) and ES lasing regime (between and ). The bistability in the two‐state regime Figure b is very similar to the one reported in and the bistability in the ES regime reproduces the behavior that was observed in . Hence two‐state QD lasers combine a variety of different bistability scenarios of a similar mechanism, among which can be chosen be selecting an appropriate operating current.…”

“…So far our numeric results did not show bistability between the different sweep directions. However, an optically induced hysteresis has been observed experimentally in a two‐state QD laser . In the following, we therefore look for bistability in our two‐state QD laser model.…”

“…Theoretical results for two‐state lasers with optical injection suggest the inhomogeneous broadening of QD states to be crucial for the observation of the hysteresis . The authors also emphasize the need for a model that goes beyond the α‐factor approximation to describe the amplitude‐phase coupling of the gain medium.…”

Dual state antiphase excitability in optically injected quantum dot lasers

“…5 The slave laser (SL) was a 0.6 mm long InAs based QD laser with single mode GS emission at approximately 1300 nm and multimode ES emission at 1220 nm. There were three distinct thresholds: the GS threshold was at 34 mA, both the GS and the ES started to operate simultaneously at 60 mA and above 80 mA emission was from the ES only.…”

“…5,6 It consists of …ve equations for the complex electric …eld of the GS, the intensity of the ES, the occupation probabilities of the GS and ES and the carrier density in the wetting layer. To induce the excitable pulses stochastic e¤ects were also included.…”