Spectral characteristics of vertical-cavity surface-emitting lasers with external optical feedback

The measurement of the effects of external optical feedback on the spectra of VCSELs (vertical-cavity surface-emitting lasers) is reported. It is surprising that VCSELs have a sensitivity to optical feedback comparable to that of conventional edge-emitting lasers such as DFBs despite their significantly different structures. This is because the extremely short cavity length of VCSELs negates the effects of their highly reflective output mirrors. As in edge-emitting lasers, VCSELs exhibit well-defined regimes of feedback effects in their spectra. Since optical isolators cannot be easily applied to VCSELs due to their array structure, these lasers may be most useful in applications which are not sensitive to the spectral qualities of the light source.<>