Effects of the linewidth enhancement factor on the microwave linewidth of the period-one oscillations of optically injected semiconductor lasers

We investigate the microwave linewidth of the period-one (P1) nonlinear dynamics of an optically injected semiconductor laser as a function of the linewidth enhancement factor. Under proper conditions of optical injection, the destabilizing effect of a large value of the linewidth enhancement factor of the injected semiconductor laser is found to be unexpectedly suppressed in the P1 oscillation of the laser, thus resulting in a narrow P1 linewidth equal to that generated by a laser of a small linewidth enhancement factor. By properly choosing the operating point, P1 oscillations with microwave linewidths that are an order of magnitude narrower than the free-running optical linewidths of the master and slave lasers are observed. (C) 2022 Optica Publishing Group