Hysteresis properties induced by variable polarization angle in the polarization switching of VCSELs

The influence of variable-polarization optical feedback (VPOF) on the polarization mode switching (PMS) properties of a vertical-cavity surface-emitting laser (VCSEL) has been investigated experimentally. Rotated-polarization optical feedback is considered. At high levels of optical feedback VCSEL exhibits an abrupt PMS when the polarization angle is swept from 0° to 90° and vice versa. We observe a hysteresis loop (HL) beyond the polarization angle of 45°, which is barely affected by the level of feedback. The experimental results demonstrate that the size of HL strongly depends on the feedback level, where a narrower and wider width HL are observed at higher and lower levels of feedback, respectively. An external optical feedback with the VPOF can significantly alter the bistability properties of PMS in VCSELs. VPOF can provide a new method to obtain the controllable bistable PMS in VCSELs, which is extremely useful for applications that use the optical bistability (OB).