Current-driven Bistability In A Semiconductor Laser Subject To Optical Injection

The optical bistability (OB) of semiconductor lasers attracted much attention for its potential applications in optical computation and optical communication fields, such as optical logic switch, optical memory, optical signal reshap, optical wavelength converter, etc. Subject to the optical injection, semiconductor lasers behave plenty of nonlinear dynamics. At the appropriate working conditions, the system output may be present optical bistability phenomenon. Early results show:the bistability can be achieved by varying the injection optical frequency or the injection optical power of master laser (ML), and can also be achieved by varying the bias current of the slave laser (SL). When the above parameters are varied along different routes to the same value, the output power of the semiconductor laser may be different, thus the power-bistability can be obtained. But recent reports show:a new style bistability has been observed in a DFB semiconductor laser under optical injection, namely state-bistability between locking and bimodal region. In this paper, the new style state-bistability has been studied further.In this paper, based on the master-slave configuration of semiconductor lasers, the bistability of master laser's output have been investigated on experiment, here, master laser injected by slave laser. In the experiment, the bistability can be obtained by the follow two ways:(1) when the laser is biased nearby the threshold, sweeping the power of ML along different routes with the fixed frequency detuningΔf (Δf=fm-fS,fM,fS corresponding main slave laser free-running frequencies), the bistability can be observed, this bistability called power driven bistability. The experimental results show that:when bias current of the slave is fixed, the bistability is exists at negative frequency detuning, and state-bistability loop width increasing with frequency detuning increasing; and state bistability loop width increasing with bias current increasing, but when bias current increase to 12.6 mA, the bistability will disappears; (2) fixed the injection power, sweeping the current of SL nearby its threshold back and forth, the bistability can be observed, this bistability called current driven bistability. The experimental results show that:for much lower injection power, only state-bistability can be observed. For suitable injection power, both power-bistability and state-bisttability can be observed, and for much large injection power, the power-bistability and state-bistability will disappear. Additionally, the bistablility loop width is affected by the injection optical power.