New approaches namely circularly polarised optical injection and circularly polarised optical feedback have been used experimentally for the first time. Using circularly polarised externally optical injection, the output polarisation of electrically pumped VCSELs can be strongly influenced. The linear polarisation of VCSELs emission can become circularly polarised for bias currents below or near the threshold current of the stand-alone VCSELs. In addition, using a new circularly polarised optical feedback scheme, the VCSELs emission was made to exhibit a degree of circular polarisation. The degree of circular polarisation depends on the feedback power ratio and the VCSEL bias current.
