Based on the framework of the spin-flip model (SFM), for the GHz level modulation frequency, the polarization
performances of current-modulated vertical-cavity surface emitting lasers (VCSELs) subject to weak optical
feedback have been theoretically investigated. The results show that, for type I polarization switching (PS), under
small signal modulation, the variation of the modulation frequency does not affect the polarization direction of the
VCSEL output, but due to the influence of the optical feedback, the VCSEL output may behave period, doubling
period and chaos state with modulation frequency variation. For the case of the large signal modulation, optical
feedback can result in the generation of a new style of PS with the variation of the modulation frequency.