Current-dependence of polarisation switching and locking in an optically injected 1550 nm vertical-cavity surface-emitting laser

The authors have studied the effects of polarised optical injection in a 1550 nm vertical-cavity surface-emitting laser (VCSEL) operated at currents up to 4.5 times threshold. Regions of stable injection locking have been measured for cases where the injected signal is polarised to match one of the two polarisations of the fundamental transverse mode of the solitary VCSEL. In addition regions of polarisation switching have been found for the case where the input polarisation is matched to that of the subsidiary mode of the solitary VCSEL. The variation of this behaviour with current has been investigated.