Linewidth Enhancement Factor Impact on Optical Feedback Mutual Coupled Quantum Dot Lasers

In this article, we numerically study and analyse the roles of linewidth enhancement factor (α) in the dynamic operation of the mutual regime of the transmitter and receiver quantum dot laser lasers supported by optical feedback. A set model of adequate rate equations describing the overall dynamics in a quantum dot system subjected to optical feedback were solved numerically. The results reveal a clear chaotic regime between the receiver and the transmitter lasers at α = 3, which is incredibly advantageous for secure optical communications and encoding decoding data transmission. Moreover, at the other value of linewidth enhancement factors, namely 2, 2.5, 3.5 and 4, the optical regime works in high synchronisation with either periodic or steady state forms.

Practical lineshape of a laser operating near an exceptional point

We present a practical laser linewidth broadening phenomenon in the viewpoint of high sensitivity of an exceptional point (EP). A stochastic simulation model is implemented to describe the fluctuations in the cavity resonance frequencies. The linewidth originated from external noises are maximized at the EP. The linewidth enhancement factor behaves similarly to the Petermann factor although the Petermann effect is not considered. In the long coherence time limit, the power spectral density of the laser exhibits a splitting in the vicinity of the EP although the cavity eigenfrequencies coalesce at the EP.