Polarization Properties of Vertical-cavity Surface-emitting Lasers Subject to Variable Optical Feedback Polarization Angle

In this paper, the influence of variable polarization angle (θp) of optical feedback (OF) on the polarization properties of a vertical-cavity surface-emitting lasers (VCSELs) is investigated experimentally. Parallel polarization optical feedback (PPOF) and orthogonal polarization optical feedback (OPOF) are employed, where the polarization light is re-injected back into the laser. For the PPOF (OPOF), polarization of the feedback light is parallel (orthogonal) to the polarization light of solitary VCSEL. With respect to PPOF, no polarization switching (PS) occurs over the entire range of θp. However, when apply both the PPOF and OPOF PS takes places for a fixed OF level and at certain value of θp with increasing bias current (Ib). Furthermore, when increasing θp PS occur for a fixed OF level and bias Ib. The results show that a variable polarization optical feedback technique is an effective tool for controlling the polarization instabilities of VCSEL.